Semiconductor device

Abstract

Provided is a semiconductor device that can be miniaturized or highly integrated. The semiconductor device includes: a first insulator; an oxide semiconductor over the first insulator; a first conductor, a second conductor, and a third insulator over the oxide semiconductor; a second insulator on the first insulator, the first conductor and the second conductor; and a third conductor on the third insulator. The oxide semiconductor has a first region overlapping the first conductor, a second region overlapping the second conductor, and a third region between the first region and the second region. The second insulator has an opening in a region overlapping the third region, and a third insulator and a third conductor are provided inside the opening. The first and second regions are in contact with the first and second insulators, and the third region is in contact with the first and third insulators. The first insulator and the second insulator each contain silicon and nitrogen.

Description

Technical Field

[0001] One aspect of the present invention relates to a semiconductor device, a storage device, and an electronic device. Another aspect of the present invention relates to a method for manufacturing the semiconductor device described above.

[0002] Note that one aspect of the present invention is not limited to the above technical field. As an example of the technical field of one aspect of the present invention, semiconductor devices, display devices, light-emitting devices, power storage devices, storage devices, electronic devices, lighting devices, input devices (e.g., touch sensors), input / output devices (e.g., touch panels), and driving methods or manufacturing methods of the above devices can be cited.

[0003] Note that in this specification and the like, a semiconductor device refers to all devices that can operate by utilizing semiconductor characteristics. In addition to semiconductor elements such as transistors, semiconductor circuits, arithmetic devices, or storage devices are also one aspect of semiconductor devices. Sometimes it can be said that display devices (liquid crystal display devices, light-emitting display devices, etc.), projection devices, lighting devices, electro-optical devices, power storage devices, storage devices, semiconductor circuits, imaging devices, electronic devices, etc. include semiconductor devices. Background Art

[0004] In recent years, semiconductor devices have been developed, and LSI (Large Scale Integrated Circuit), CPU (Central Processing Unit), memories, etc. are mainly used for semiconductor devices. A CPU is an aggregate of semiconductor elements including a semiconductor integrated circuit formed by processing a semiconductor wafer to form a chip (including at least transistors and memories) and having electrodes as connection terminals.

[0005] Semiconductor circuits (IC chips) such as LSI, CPU, and memories are mounted on a circuit board (e.g., printed wiring board) and are used as one of the components of various electronic devices.

[0006] In addition, a technique of forming a transistor using a semiconductor thin film formed on a substrate having an insulating surface has attracted attention. This transistor is widely used in electronic devices such as integrated circuits (ICs) and image display devices (simply referred to as display devices). As a semiconductor thin film that can be applied to a transistor, silicon-based semiconductor materials are widely known. As other materials, oxide semiconductors have attracted attention.

[0007] In addition, it is known that a transistor using an oxide semiconductor has an extremely small leakage current in the non-conducting state. For example, Patent Document 1 has disclosed a low-power CPU or the like that utilizes the characteristic of a small leakage current of a transistor using an oxide semiconductor. In addition, for example, Patent Document 2 has disclosed a storage device or the like that can achieve long-term retention of stored content by utilizing the characteristic of a small leakage current of a transistor using an oxide semiconductor.

[0008] In recent years, with the miniaturization and weight reduction of electronic devices, the demand for further high-density integration of integrated circuits has increased. In addition, it is required to improve the productivity of semiconductor devices including integrated circuits. For example, Patent Document 3 and Non-Patent Document 1 have disclosed a technique in which a plurality of memory cells are overlapped by laminating a first transistor using an oxide semiconductor film and a second transistor using an oxide semiconductor film, thereby increasing the density of the integrated circuit. In addition, for example, as shown in Patent Document 4, a technique has also been disclosed in which the channels of transistors using an oxide semiconductor film are vertically arranged to achieve high-density integration of the integrated circuit.

[0009] [Prior Art Documents]

[0010] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-257187

[0012] [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-151383

[0013] [Patent Document 3] International Patent Application Publication No. 2021 / 053473

[0014] [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-211537

[0015] [Non-Patent Documents]

[0016] [Non-Patent Document 1] M.Oota et al., “3D-Stacked CAAC-In-Ga-Zn Oxide FETs with Gate Length of 72nm”, IEDM Tech. Dig., 2019, pp.50-53 Summary of the Invention

[0017] Technical Problem to be Solved by the Invention

[0018] One of the objects of one embodiment of the present invention is to provide a semiconductor device that can be miniaturized or highly integrated. One of the objects of one embodiment of the present invention is to provide a semiconductor device with a high operating speed. One of the objects of one embodiment of the present invention is to provide a semiconductor device having excellent electrical characteristics. One of the objects of one embodiment of the present invention is to provide a semiconductor device in which the electrical characteristics of transistors are less uneven. One of the objects of one embodiment of the present invention is to provide a semiconductor device with high reliability. One of the objects of one embodiment of the present invention is to provide a semiconductor device with a large on-state current. One of the objects of one embodiment of the present invention is to provide a low-power semiconductor device. One of the objects of one embodiment of the present invention is to provide a novel semiconductor device. One of the objects of one embodiment of the present invention is to provide a method for manufacturing a semiconductor device with high productivity. One of the objects of one embodiment of the present invention is to provide a novel method for manufacturing a semiconductor device.

[0019] In addition, one of the objects of one embodiment of the present invention is to provide a storage device that can be miniaturized or highly integrated. One of the objects of one embodiment of the present invention is to provide a storage device with a large storage capacity. One of the objects of one embodiment of the present invention is to provide a storage device with a high operating speed. One of the objects of one embodiment of the present invention is to provide a low-power storage device. One of the objects of one embodiment of the present invention is to provide a novel storage device.

[0020] Note that the description of these objects does not preclude the existence of other objects. One embodiment of the present invention does not need to achieve all of the above objects. Objects other than the above can be extracted from the description of the specification, drawings, and claims.

[0021] Means for Solving the Technical Problem

[0022] One embodiment of the present invention is a semiconductor device including: a first insulator; an oxide semiconductor on the first insulator; a first conductor and a second conductor on the oxide semiconductor; a second insulator on the first insulator, the first conductor, and the second conductor; a third insulator on the oxide semiconductor; and a third conductor on the third insulator, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region located between the first region and the second region, the second insulator has an opening in a region overlapping with the third region, at least a part of each of the third insulator and the third conductor is provided inside the opening, both the first region and the second region are in contact with the first insulator and the second insulator, the third region is in contact with the first insulator and the third insulator, both the first insulator and the second insulator contain silicon and nitrogen, and the first insulator has a region with a thickness of 1.0 nm or more and 5.0 nm or less.

[0023] Further, one aspect of the present invention is a semiconductor device including: a first insulator; an oxide semiconductor on the first insulator; a first conductor and a second conductor on the oxide semiconductor; a second insulator on the first insulator, the first conductor, and the second conductor; a third insulator on the oxide semiconductor; a third conductor on the third insulator; and a fourth insulator on the third insulator and the third conductor, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region located between the first region and the second region, the second insulator has an opening in a region overlapping with the third region, at least a part of each of the third insulator and the third conductor is disposed inside the opening, both the first region and the second region are in contact with the first insulator and the second insulator, the third region is in contact with the first insulator and the third insulator, the first insulator, the second insulator, and the fourth insulator each contain silicon and nitrogen, the first insulator has a region with a thickness smaller than that of the fourth insulator, and the concentration of impurity elements in the first insulator is higher than the concentration of impurity elements in the fourth insulator.

[0024] In the above semiconductor device, preferably, the impurity element is fluorine, chlorine, bromine, iodine, hydrogen, or carbon.

[0025] In the above semiconductor device, preferably, a fourth conductor is further included under the first insulator, and the fourth conductor has a region overlapping with the third conductor with the first insulator, the oxide semiconductor, and the third insulator therebetween.

[0026] In the above semiconductor device, preferably, the first insulator is strip-shaped and is disposed to extend in a direction in which the third conductor extends.

[0027] In the above semiconductor device, preferably, the first insulator is island-shaped, a side end portion of the first insulator coincides with a side end portion of the oxide semiconductor, and the second insulator is in contact with a side surface of the first insulator.

[0028] In the above semiconductor device, preferably, a side surface of the third region of the oxide semiconductor near the second insulator includes crystals, the crystals have a crystal structure in which a plurality of layers are stacked, and the layers included in the crystals extend in a direction parallel or substantially parallel to the side surface of the oxide semiconductor.

[0029] One aspect of the present invention is a semiconductor device, which includes: a first insulator; a second insulator on the first insulator; an oxide semiconductor located on the first insulator and covering the top surface and side surfaces of the second insulator; a first conductor and a second conductor on the oxide semiconductor; a third insulator on the first insulator, the first conductor, and the second conductor; a fourth insulator on the oxide semiconductor; and a third conductor on the fourth insulator, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region located between the first region and the second region, the third insulator has an opening in a region overlapping with the third region, at least a part of each of the fourth insulator and the third conductor is provided inside the opening, both the first region and the second region are in contact with the first insulator, the second insulator, and the third insulator, the third region is in contact with the first insulator, the second insulator, and the fourth insulator, the first insulator, the second insulator, and the third insulator all contain silicon and nitrogen, and the first insulator has a region with a thickness of 1.0 nm or more and 5.0 nm or less.

[0030] In the above semiconductor device, preferably, the height of the second insulator is greater than the length of the second insulator in the direction in which the third conductor extends.

[0031] In the above semiconductor device, preferably, a fifth insulator is further included on the fourth insulator and the third conductor, the first insulator has a region with a thickness smaller than that of the fifth insulator, and the concentration of impurity elements in the first insulator is higher than the concentration of impurity elements in the fifth insulator.

[0032] In the above semiconductor device, preferably, the impurity element is fluorine, chlorine, bromine, iodine, hydrogen, or carbon.

[0033] In the above semiconductor device, preferably, the side surface of the third region of the oxide semiconductor near the fourth insulator contains crystals, the crystals have a crystal structure in which a plurality of layers are stacked, and the layers included in the crystals extend in a parallel or substantially parallel manner to the surface of the oxide semiconductor.

[0034] One aspect of the present invention is a semiconductor device, which includes: a first insulator; a second insulator, a third insulator on the first insulator, and a fourth insulator located between the second insulator and the third insulator; an oxide semiconductor on the second insulator, the third insulator, and the fourth insulator; a first conductor and a second conductor on the oxide semiconductor; a fifth insulator on the first insulator, the first conductor, and the second conductor; a sixth insulator on the oxide semiconductor; and a third conductor on the sixth insulator, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region located between the first region and the second region, the fifth insulator has an opening in a region overlapping with the third region, at least a part of each of the sixth insulator and the third conductor is provided inside the opening, the first region contacts the second insulator and the fifth insulator, the second region contacts the third insulator and the fifth insulator, the third region contacts the fourth insulator and the sixth insulator, the second insulator, the third insulator, and the fifth insulator all contain silicon and nitrogen, the thicknesses of the second insulator, the third insulator, and the fourth insulator are the same as each other, and the second insulator has a region with a thickness of 1.0 nm or more and 5.0 nm or less.

[0035] One aspect of the present invention is a semiconductor device, which includes: a first insulator; a second insulator, a third insulator on the first insulator, and a fourth insulator located between the second insulator and the third insulator; an oxide semiconductor on the second insulator, the third insulator, and the fourth insulator; a first conductor and a second conductor on the oxide semiconductor; a fifth insulator on the first insulator, the first conductor, and the second conductor; a sixth insulator on the oxide semiconductor; a third conductor on the sixth insulator; and a seventh insulator on the sixth insulator and the third conductor, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region located between the first region and the second region, the fifth insulator has an opening in a region overlapping with the third region, at least a part of each of the sixth insulator and the third conductor is provided inside the opening, the first region contacts the second insulator and the fifth insulator, the second region contacts the third insulator and the fifth insulator, the third region contacts the fourth insulator and the sixth insulator, the second insulator, the third insulator, the fifth insulator, and the seventh insulator all contain silicon and nitrogen, the thicknesses of the second insulator, the third insulator, and the fourth insulator are the same as each other, the second insulator has a region with a thickness smaller than that of the seventh insulator, and the concentration of impurity elements in the second insulator is higher than the concentration of impurity elements in the seventh insulator.

[0036] In the above semiconductor device, preferably, the impurity element is fluorine, chlorine, bromine, iodine, hydrogen, or carbon.

[0037] In the above-described semiconductor device, preferably, a fourth conductor is further included under the first insulator, and the fourth conductor has a region overlapping with the third conductor with the first insulator, the fourth insulator, the oxide semiconductor, and the sixth insulator therebetween.

[0038] In the above-described semiconductor device, preferably, the second insulator, the third insulator, and the fourth insulator are each strip-shaped and are arranged to extend in the direction in which the third conductor extends.

[0039] In the above-described semiconductor device, preferably, the second insulator, the third insulator, and the fourth insulator are each island-shaped, a side end portion of the second insulator coincides with a side end portion of the oxide semiconductor, a side end portion of the third insulator coincides with a side end portion of the oxide semiconductor, a side end portion of the fourth insulator coincides with a side end portion of the oxide semiconductor, and the fifth insulator contacts side surfaces of the second insulator and the third insulator.

[0040] In the above-described semiconductor device, preferably, a third region of the oxide semiconductor includes crystals on a side surface near the sixth insulator, the crystals have a crystal structure in which a plurality of layers are stacked, and the layers included in the crystals extend in a direction parallel or substantially parallel to the side surface of the oxide semiconductor.

[0041] One aspect of the present invention is a semiconductor device including: a first insulator; a second insulator, a third insulator on the first insulator, and a fourth insulator between the second insulator and the third insulator; a fifth insulator on the second insulator, the third insulator, and the fourth insulator; an oxide semiconductor covering a top surface and side surfaces of the fifth insulator on the second insulator, the third insulator, and the fourth insulator; a first conductor and a second conductor on the oxide semiconductor; a sixth insulator on the first insulator, the first conductor, and the second conductor; a seventh insulator on the oxide semiconductor; and a third conductor on the seventh insulator, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region between the first region and the second region, the sixth insulator has an opening in a region overlapping with the third region, at least a part of each of the seventh insulator and the third conductor is provided inside the opening, the first region contacts the second insulator, the fifth insulator, and the sixth insulator, the second region contacts the third insulator, the fifth insulator, and the sixth insulator, the third region contacts the fourth insulator, the fifth insulator, and the seventh insulator, the second insulator, the third insulator, the fifth insulator, and the seventh insulator all contain silicon and nitrogen, the thicknesses of the second insulator, the third insulator, and the fourth insulator are the same as each other, and the second insulator has a region with a thickness of 1.0 nm or more and 5.0 nm or less.

[0042] In the above semiconductor device, preferably, the height of the fifth insulator is greater than the length of the fifth insulator in the direction in which the third conductor extends.

[0043] In the above semiconductor device, preferably, an eighth insulator is further included on the seventh insulator and the third conductor, the second insulator has a region with a thickness smaller than that of the eighth insulator, and the concentration of impurity elements in the second insulator is higher than the concentration of impurity elements in the eighth insulator.

[0044] In the above semiconductor device, preferably, the impurity element is fluorine, chlorine, bromine, iodine, hydrogen, or carbon.

[0045] In the above semiconductor device, preferably, the third region of the oxide semiconductor includes crystals on the side surface near the seventh insulator, the crystals have a crystal structure in which a plurality of layers are stacked, and the layers included in the crystals extend in a direction parallel or substantially parallel to the surface of the oxide semiconductor.

[0046] Advantages of the Invention

[0047] According to one aspect of the present invention, a semiconductor device capable of miniaturization or high integration can be provided. According to one aspect of the present invention, a semiconductor device with a high operating speed can be provided. According to one aspect of the present invention, a semiconductor device having excellent electrical characteristics can be provided. According to one aspect of the present invention, a semiconductor device in which the non-uniformity of the electrical characteristics of a transistor is small can be provided. According to one aspect of the present invention, a highly reliable semiconductor device can be provided. According to one aspect of the present invention, a semiconductor device with a large on-state current can be provided. According to one aspect of the present invention, a low-power semiconductor device can be provided. According to one aspect of the present invention, a novel semiconductor device can be provided. According to one aspect of the present invention, a method for manufacturing a semiconductor device with high productivity can be provided. According to one aspect of the present invention, a method for manufacturing a novel semiconductor device can be provided.

[0048] In addition, according to one aspect of the present invention, a storage device capable of miniaturization or high integration can be provided. According to one aspect of the present invention, a storage device with a large storage capacity can be provided. According to one aspect of the present invention, a storage device with a high operating speed can be provided. According to one aspect of the present invention, a low-power storage device can be provided. According to one aspect of the present invention, a novel storage device can be provided.

[0049] Note that the description of these effects does not preclude the existence of other effects. One aspect of the present invention does not necessarily have all of the above effects. Effects other than the above can be extracted from the description in the specification, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1A is a plan view showing an example of a semiconductor device. Figures 1B to 1D is a cross-sectional view showing an example of a semiconductor device. Figure 1E is a three-dimensional schematic diagram showing an example of a semiconductor device.

[0051] Figure 2A and Figure 2B is a cross-sectional view showing an example of a semiconductor device.

[0052] Figure 3A and Figure 3B is a cross-sectional view showing an example of a semiconductor device.

[0053] Figure 4A is a plan view showing an example of a semiconductor device. Figures 4B to 4D is a cross-sectional view showing an example of a semiconductor device.

[0054] Figure 5A is a plan view showing an example of a semiconductor device. Figures 5B to 5D is a cross-sectional view showing an example of a semiconductor device.

[0055] Figure 6A is a plan view showing an example of a semiconductor device. Figures 6B to 6D is a cross-sectional view showing an example of a semiconductor device.

[0056] Figure 7A is a plan view showing an example of a semiconductor device. Figures 7B to 7D is a cross-sectional view showing an example of a semiconductor device.

[0057] Figure 8A is a plan view showing an example of a semiconductor device. Figures 8B to 8D is a cross-sectional view showing an example of a semiconductor device.

[0058] Figure 9A is a plan view showing an example of a semiconductor device. Figures 9B to 9D is a cross-sectional view showing an example of a semiconductor device.

[0059] Figure 10A is a plan view showing an example of a semiconductor device. Figures 10B to 10D is a cross-sectional view showing an example of a semiconductor device.

[0060] Figure 11A is a plan view showing an example of a semiconductor device. Figures 11B to 11D is a cross-sectional view showing an example of a semiconductor device.

[0061] Figure 12A is a plan view showing an example of a semiconductor device.Figures 12B to 12D It is a cross-sectional view showing an example of a semiconductor device.

[0062] Figure 13A It is a plan view showing an example of a semiconductor device. Figures 13B to 13D It is a cross-sectional view showing an example of a semiconductor device.

[0063] Figure 14A It is a plan view showing an example of a semiconductor device. Figures 14B to 14D It is a cross-sectional view showing an example of a semiconductor device. Figure 14E It is a three-dimensional schematic view showing an example of a semiconductor device.

[0064] Figure 15 It is a cross-sectional view showing an example of a semiconductor device.

[0065] Figure 16A It is a plan view showing an example of a semiconductor device. Figures 16B to 16D It is a cross-sectional view showing an example of a semiconductor device.

[0066] Figure 17A It is a plan view showing an example of a semiconductor device. Figures 17B to 17D It is a cross-sectional view showing an example of a semiconductor device.

[0067] Figure 18A It is a plan view showing an example of a semiconductor device. Figures 18B to 18D It is a cross-sectional view showing an example of a semiconductor device.

[0068] Figure 19A It is a plan view showing an example of a semiconductor device. Figures 19B to 19D It is a cross-sectional view showing an example of a semiconductor device.

[0069] Figure 20A It is a plan view showing an example of a semiconductor device. Figures 20B to 20D It is a cross-sectional view showing an example of a semiconductor device.

[0070] Figure 21A It is a plan view showing an example of a semiconductor device. Figures 21B to 21D It is a cross-sectional view showing an example of a semiconductor device.

[0071] Figure 22A It is a plan view showing an example of a semiconductor device. Figures 22B to 22D It is a cross-sectional view showing an example of a semiconductor device.

[0072] Figure 23A It is a plan view showing an example of a semiconductor device. Figures 23B to 23D It is a cross-sectional view showing an example of a semiconductor device.

[0073] Figure 24A is a plan view showing an example of a semiconductor device. Figures 24B to 24D is a cross-sectional view showing an example of a semiconductor device.

[0074] Figure 25A is a plan view showing an example of a semiconductor device. Figures 25B to 25D is a cross-sectional view showing an example of a semiconductor device.

[0075] Figure 26A is a plan view showing an example of a semiconductor device. Figures 26B to 26D is a cross-sectional view showing an example of a semiconductor device.

[0076] Figure 27A is a plan view showing an example of a semiconductor device. Figures 27B to 27D is a cross-sectional view showing an example of a semiconductor device.

[0077] Figure 28A is a plan view showing an example of a semiconductor device. Figures 28B to 28D is a cross-sectional view showing an example of a semiconductor device.

[0078] Figure 29A is a plan view showing an example of a semiconductor device. Figures 29B to 29D is a cross-sectional view showing an example of a semiconductor device.

[0079] Figure 30A is a plan view showing an example of a semiconductor device. Figures 30B to 30D is a cross-sectional view showing an example of a semiconductor device.

[0080] Figure 31A is a plan view showing an example of a semiconductor device. Figures 31B to 31D is a cross-sectional view showing an example of a semiconductor device.

[0081] Figure 32A is a plan view showing an example of a semiconductor device. Figures 32B to 32D is a cross-sectional view showing an example of a semiconductor device.

[0082] Figure 33A is a plan view showing an example of a semiconductor device. Figures 33B to 33D is a cross-sectional view showing an example of a semiconductor device.

[0083] Figure 34A and Figure 34B is a cross-sectional view showing an example of a semiconductor device.

[0084] Figure 35A and Figure 35BIt is a cross-sectional view showing an example of a semiconductor device.

[0085] Figure 36A It is a plan view showing an example of a semiconductor device. Figures 36B to 36D It is a cross-sectional view showing an example of a semiconductor device.

[0086] Figure 37A It is a plan view showing an example of a semiconductor device. Figures 37B to 37D It is a cross-sectional view showing an example of a semiconductor device.

[0087] Figures 38A to 38C It is a cross-sectional view showing an example of a semiconductor device.

[0088] Figures 39A to 39C It is a cross-sectional view showing an example of a semiconductor device.

[0089] Figure 40A It is a plan view showing an example of a semiconductor device. Figures 40B to 40D It is a cross-sectional view showing an example of a semiconductor device.

[0090] Figure 41A It is a plan view showing an example of a semiconductor device. Figures 41B to 41D It is a cross-sectional view showing an example of a semiconductor device.

[0091] Figure 42 It is a cross-sectional view showing an example of a semiconductor device.

[0092] Figures 43A to 43D It is a cross-sectional view showing an example of a semiconductor device.

[0093] Figures 44A to 44C It is a cross-sectional view showing an example of a semiconductor device.

[0094] Figure 45A It is a plan view showing an example of a semiconductor device. Figures 45B to 45D It is a cross-sectional view showing an example of a semiconductor device.

[0095] Figure 46A It is a plan view showing an example of a semiconductor device. Figures 46B to 46D It is a cross-sectional view showing an example of a semiconductor device.

[0096] Figure 47A and Figure 47B It is a cross-sectional view showing an example of a semiconductor device.

[0097] Figures 48A to 48C It is a cross-sectional view showing an example of a semiconductor device.

[0098] Figures 49A to 49CIt is a cross-sectional view showing an example of a semiconductor device.

[0099] Figure 50A It is a plan view showing an example of a semiconductor device. Figures 50B to 50D It is a cross-sectional view showing an example of a semiconductor device.

[0100] Figure 51 It is a block diagram showing an example of a storage device.

[0101] Figure 52A and Figure 52B It is a schematic diagram and a circuit diagram showing an example of a storage device.

[0102] Figure 53A and Figure 53B It is a schematic diagram showing an example of a storage device.

[0103] Figure 54 It is a circuit diagram showing an example of a storage device.

[0104] Figure 55A and Figure 55B It is a cross-sectional view showing an example of a storage device.

[0105] Figure 56A and Figure 56B It is a cross-sectional view showing an example of a storage device.

[0106] Figure 57 It is a cross-sectional view showing an example of a storage device.

[0107] Figure 58A and Figure 58B It is a diagram showing an example of a semiconductor device.

[0108] Figure 59A and Figure 59B It is a diagram showing an example of an electronic component.

[0109] Figure 60A and Figure 60B It is a diagram showing an example of an electronic device, Figures 60C to 60E It is a diagram showing an example of a mainframe computer.

[0110] Figure 61 It is a diagram showing an example of a space device.

[0111] Figure 62 It is a diagram showing an example of a storage system that can be used in a data center.

[0112] Figure 63 It is a diagram explaining the stacked structure of a stacked film.

[0113] Figure 64A andFigure 64B These are the results of SIMS analysis of the fabricated samples.

[0114] Figures 65A to 65C These are the SIMS analysis results of the fabricated samples. Detailed Embodiments

[0115] The embodiments will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following description, and those of ordinary skill in the art can easily understand the fact that its mode and details can be changed into various forms without departing from the gist and scope of the present invention. Therefore, the present invention should not be construed as being limited only to the content described in the embodiments shown below.

[0116] Note that in the inventive structures described below, the same reference numerals are used in different drawings to denote the same parts or parts having the same functions, and repeated descriptions are omitted. In addition, when denoting parts having the same functions, the same hatching is sometimes used without particularly attaching reference numerals.

[0117] In addition, for ease of understanding, the positions, sizes, and ranges of the respective components shown in the drawings do not necessarily represent their actual positions, sizes, and ranges. Therefore, the disclosed invention is not necessarily limited to the positions, sizes, and ranges disclosed in the drawings.

[0118] In addition, especially in a plan view (also called a top view) or a perspective view, etc., for ease of understanding of the invention, the description of some components may be omitted. In addition, the description of some hidden lines may be omitted.

[0119] Note that in this specification, etc., for convenience, ordinal numbers such as "first" and "second" are added, and they do not limit the number of components or the order of components (for example, the process order or the stacking order). In addition, the ordinal numbers attached to a component in a part of this specification may sometimes be inconsistent with the ordinal numbers attached to the same component in other parts of this specification or in the claims.

[0120] In addition, depending on the situation or circumstances, "film" and "layer" can be interchanged with each other. For example, "conductive layer" can be changed to "conductive film". In addition, "insulating film" can be changed to "insulating layer". In addition, depending on the situation or circumstances, "conductor" can be interchanged with "conductive layer" or "conductive film". In addition, depending on the situation or circumstances, "insulator" can be interchanged with "insulating layer" or "insulating film".

[0121] In this specification and the like, "parallel" means a state in which the angle formed by two straight lines is -10 degrees or more and 10 degrees or less. Therefore, it also includes a state in which the angle is -5 degrees or more and 5 degrees or less. "Substantially parallel" means a state in which the angle formed by two straight lines is -30 degrees or more and 30 degrees or less. In addition, "perpendicular" means a state in which the angle between two straight lines is 80 degrees or more and 100 degrees or less. Therefore, it also includes a state in which the angle is 85 degrees or more and 95 degrees or less. "Substantially perpendicular" means a state in which the angle formed by two straight lines is 60 degrees or more and 120 degrees or less.

[0122] The opening includes, for example, a groove, a slit, and the like. In addition, the region where the opening is formed is sometimes referred to as an opening portion.

[0123] In addition, the drawings used in this embodiment show the case where the side wall of the opening of the insulator is perpendicular or substantially perpendicular to the substrate surface or the formation surface, but the side wall may also have a conical shape.

[0124] Note that in this specification and the like, the conical shape means a shape in which at least a part of the side surface of the component is inclined with respect to the substrate surface or the formation surface. For example, it has a region where the angle formed by the inclined side surface and the substrate surface or the formation surface (hereinafter sometimes referred to as the cone angle) is less than 90°. Note that the side surface of the component and the substrate surface do not necessarily have to be completely flat, and may be an approximately planar shape with a minute curvature or an approximately planar shape with fine unevenness.

[0125] Note that in this specification and the like, "the same height" means a structure in which the heights from a reference surface (for example, a flat surface such as the substrate surface) are equal in a cross section. For example, in the manufacturing process of a storage device, a planarization process (typically a CMP (Chemical Mechanical Polishing) process) is sometimes performed to expose the surface of a single layer or multiple layers. At this time, the surface to be processed by the CMP process has a structure in which the heights from the reference surface are equal. However, depending on the processing device, processing method, or material of the surface to be processed used in the CMP process, the heights of multiple layers may sometimes be different. In this specification and the like, "the same height" also includes the above cases. For example, in the case of including layers having two heights with respect to the reference surface (hereinafter referred to as the first layer and the second layer), when the difference in height between the top surface of the first layer and the top surface of the second layer is 20 nm or less, it is also referred to as "the same height".

[0126] Note that in this specification and the like, "the side ends coincide" means that at least a part of the outlines between the stacked layers overlaps when viewed from above. For example, it includes the case where the upper layer and the lower layer are processed by the same mask pattern or a part of the same mask pattern. However, strictly speaking, there are cases where the outlines do not overlap and the outline of the upper layer is inside the outline of the lower layer or the outline of the upper layer is outside the outline of the lower layer, and these cases can also be said to be "the side ends coincide".

[0127] Note that generally, it is difficult to clearly distinguish between "completely coincide" and "substantially coincide". Therefore, in this specification and the like, "coincide" includes both the case of complete coincidence and the case of substantial coincidence.

[0128] Note that in this specification and the like, the first thickness coincides with the second thickness means that the value obtained by dividing the absolute value of the difference between the first thickness and the second thickness by the first thickness is 0.1 or less. Or, it means that the value obtained by dividing the absolute value of the difference between the first thickness and the second thickness by the second thickness is 0.1 or less.

[0129] Note that in this specification and the like, the distance A coincides with the distance B means that the value obtained by dividing the absolute value of the difference between the distance A and the distance B by the distance A is 0.1 or less. Or, it means that the value obtained by dividing the absolute value of the difference between the distance A and the distance B by the distance B is 0.1 or less.

[0130] (Embodiment 1)

[0131] In this embodiment, with reference to Figures 1A to 32D an example of the structure of a semiconductor device according to one aspect of the present invention will be described. A semiconductor device according to one aspect of the present invention includes a transistor.

[0132] In Figures 1A to 1D , Figures 4A to 14D , Figures 16A to 32D , each Figure A shows a plan view of the semiconductor device. In addition, each Figure B is a cross-sectional view corresponding to the portion indicated by the dotted line A1 - A2 in each Figure A, and is also a cross-sectional view in the channel length direction of the transistor. In addition, each Figure C is a cross-sectional view corresponding to the portion indicated by the dotted line A3 - A4 in each Figure A, and is also a cross-sectional view in the channel width direction of the transistor. Each Figure D is a cross-sectional view corresponding to the portion indicated by the dotted line A5 - A6 in each Figure A. For clarity, some constituent elements are omitted in the plan view of each Figure A.

[0133] <Structural Example 1>

[0134] [Structural Example 1 - 1]

[0135] With reference to Figures 1A to 1D an example of the structure of the semiconductor device will be described. Figures 1A to 1D are a plan view and a cross-sectional view of a semiconductor device including a transistor 200.

[0136] Figures 1A to 1D The semiconductor device shown includes an insulator 222 on a substrate (not shown), a transistor 200 on the insulator 222, an insulator 280 on the transistor 200, and an insulator 283 on the insulator 280. The insulator 222, the insulator 280, and the insulator 283 are used as interlayer insulating films.

[0137] The transistor 200 includes an insulator 223 on the insulator 222, an oxide semiconductor 230 on the insulator 223, conductors 242a and 242b on the oxide semiconductor 230, an insulator 275 on the insulator 223, the conductors 242a, and the conductor 242b, an insulator 250 on the oxide semiconductor 230, and a conductor 260 on the insulator 250 and overlapping a part of the oxide semiconductor 230.

[0138] The conductor 260 is used as a gate electrode of the transistor 200. The insulator 250 is used as a gate insulator of the transistor 200. In addition, one of the conductors 242a and 242b is used as one of a source electrode and a drain electrode of the transistor 200, and the other conductor 242b is used as the other of the source electrode and the drain electrode of the transistor 200. Further, at least a part of the region of the oxide semiconductor 230 overlapping the conductor 260 is used as a channel formation region of the transistor 200.

[0139] Figure 1E A perspective schematic view showing the above semiconductor device is shown. In Figure 1E a part of the insulator 222, the insulator 223, the oxide semiconductor 230, the conductor 242b, the insulator 250, the conductor 260, the insulator 275, and their peripheries is cut away and shown. In addition, in Figure 1E a part of the constituent elements (for example, the insulator 280 and the insulator 283) are shown only by their outlines in dashed lines.

[0140] The oxide semiconductor 230 is provided in contact with the top surface of the insulator 223.

[0141] The conductors 242a and 242b are provided in contact with the top surface of the oxide semiconductor 230.

[0142] The insulator 275 is disposed on the insulator 223, the oxide semiconductor 230, the conductors 242a, and the conductor 242b. Specifically, the insulator 275 is provided in contact with the top surface of the insulator 223, the side surface of the oxide semiconductor 230, the top surface and the side surfaces of the conductor 242a, and the top surface and the side surfaces of the conductor 242b.

[0143] The insulator 280 is provided in contact with the top surface of the insulator 275.

[0144] An opening reaching the oxide semiconductor 230 is provided in each of the insulators 280 and 275. In addition, an opening is provided in the insulator 223 in a region of the opening that does not overlap with the oxide semiconductor 230. Hereinafter, the opening provided in the insulator 280 is referred to as the first opening, the opening provided in the insulator 275 is referred to as the second opening, and the opening provided in the insulator 223 is referred to as the third opening. In addition, the first opening, the second opening, and the third opening are collectively referred to as the opening 290.

[0145] The insulator 250 and the conductor 260 are provided inside the opening 290. In other words, at least a part of each of the insulator 250 and the conductor 260 is provided inside the first opening, inside the second opening, and inside the third opening. In addition, the insulator 250 and the conductor 260 are provided between the conductors 242a and 242b in the channel length direction of the transistor 200.

[0146] The insulator 250 contacts the side surfaces of the insulator 280 and the insulator 275 in the opening 290. In addition, the insulator 250 contacts the side surfaces of the conductors 242a and 242b on the side of the conductor 260. In addition, as Figure 1C shown, the insulator 250 contacts the top surface and the side surface of the oxide semiconductor 230, the side surface of the insulator 223, and the top surface of the insulator 222 in the opening 290.

[0147] The conductor 260 is formed self-aligned so as to fill the opening 290. By forming the conductor 260 in this way, the conductor 260 can be surely arranged in the region between the conductors 242a and 242b without alignment. In addition, the height of the top surface of the conductor 260 is the same as that of the insulator 250 and the insulator 280.

[0148] Note that in Figure 1B , the side wall of the opening 290 is perpendicular or substantially perpendicular to the formed surface of the oxide semiconductor 230, but the present embodiment is not limited thereto. For example, the bottom surface of the opening 290 may have a U-shaped shape with a gentle curved surface. For example, the side wall of the opening 290 may have a tapered shape. Here, the side wall of the opening 290 corresponds to the side surface of the insulator 280 in the opening 290, the side surface of the insulator 275 in the opening 290, and the side surface of the insulator 223 in the opening 290.

[0149] The insulator 283 is disposed on the insulator 280, the insulator 250, and the conductor 260. Preferably, in the transistor 200, a metal oxide (also referred to as an oxide semiconductor) that serves as a semiconductor is used for the oxide semiconductor 230 including the channel formation region. As the oxide semiconductor 230, a single layer or a stack of metal oxides described in [Metal Oxide] to be described later can be used.

[0150] Specifically, as the oxide semiconductor 230, a metal oxide having a composition of In:M:Zn = 1:3:2 [atomic ratio] or around it, In:M:Zn = 1:3:4 [atomic ratio] or around it, In:M:Zn = 1:1:0.5 [atomic ratio] or around it, In:M:Zn = 1:1:1 [atomic ratio] or around it, In:M:Zn = 1:1:1.2 [atomic ratio] or around it, In:M:Zn = 1:1:2 [atomic ratio] or around it, or In:M:Zn = 4:2:3 [atomic ratio] or around it can be used. Note that the composition around it includes a range of ±30% of the desired atomic ratio. In addition, gallium is preferably used as the element M.

[0151] The oxide semiconductor 230 may not contain the element M. For example, an In-Zn oxide can also be used as the metal oxide serving as the oxide semiconductor 230. Specifically, the oxide semiconductor 230 may have a composition of In:Zn = 1:1 [atomic ratio] or around it, or In:Zn = 4:1 [atomic ratio] or around it.

[0152] For the analysis of the composition of the metal oxide used for the oxide semiconductor 230, for example, energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS), or inductively coupled plasma atomic emission spectrometry (ICP-AES) can be used. Alternatively, multiple of the above methods can be combined for analysis. Note that elements with low contents are sometimes affected by the analysis accuracy, and the actual content is different from the content obtained by analysis. For example, when the content of the element M is low, the content of the element M obtained by analysis is sometimes lower than the actual content.

[0153] The metal oxide can be appropriately formed by sputtering or atomic layer deposition (ALD: Atomic Layer Deposition). Note that, when the metal oxide is formed by sputtering, the composition of the formed metal oxide is sometimes different from that of the sputtering target. In particular, the zinc content in the formed metal oxide sometimes decreases to about 50% of the sputtering target.

[0154] Examples of the ALD method include the thermal ALD (Thermal ALD) method in which only heat energy is used to react the precursor and the reactant, and the plasma ALD (PEALD: Plasma Enhanced ALD) method in which the reactant excited by plasma is used.

[0155] The ALD method can deposit atoms layer by layer, and thus has effects such as being able to deposit extremely thinly, being able to deposit on a structure with a high aspect ratio or a surface with large steps, being able to deposit in a manner with few defects such as pinholes, being able to perform high-coverage deposition, and being able to deposit at low temperatures. In addition, in the PEALD method, deposition can be performed at a lower temperature by using plasma, so it is sometimes preferred. In addition, the precursors used in the ALD method sometimes contain elements such as carbon or chlorine. Therefore, the film formed by the ALD method sometimes contains more elements such as carbon or chlorine than the film formed by other deposition methods. In addition, the quantification of these elements can be performed by XPS or secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry). Note that, in the deposition method of the metal oxide according to one embodiment of the present invention, since the ALD method is used and one or both of the conditions of a high substrate temperature during deposition and an impurity removal treatment are employed, the carbon content and chlorine content in the film are sometimes less than those in the case where the ALD method is used without these conditions.

[0156] The ALD method is different from deposition methods that deposit particles released from a target or the like, and is a deposition method that forms a film due to a reaction on the surface of the object to be processed. Therefore, the ALD method is a deposition method that is not easily affected by the shape of the object to be processed and has high step coverage. In particular, the ALD method has good step coverage and thickness uniformity, so the ALD method is suitable for forming a film that covers the surface of an opening with a high aspect ratio. However, the deposition rate of the ALD method is relatively slow, so it is sometimes preferable to use it in combination with other deposition methods such as a sputtering method or a CVD method with a high deposition rate. For example, when a metal oxide has a stacked structure of a first metal oxide and a second metal oxide, a method of depositing the first metal oxide by a sputtering method and depositing the second metal oxide on the first metal oxide by an ALD method can be cited. For example, when the above-mentioned first metal oxide has a crystalline part, the above-mentioned second metal oxide sometimes crystallizes and grows with the crystalline part as a nucleus.

[0157] The ALD method can control the composition of the obtained film according to the introduction amount of the source gas. For example, when using the ALD method, a film with an arbitrary composition can be deposited by adjusting the introduction amount of the source gas, the number of introductions (also referred to as the number of pulses), and the time required for one pulse (also referred to as the pulse time). In addition, for example, when using the ALD method, a film with a continuously changing composition can be deposited by changing the source gas while performing deposition. When depositing while changing the source gas, since the time required for transfer and pressure adjustment is not required, the deposition time can be shortened compared to the case of depositing using multiple deposition chambers. Therefore, the productivity of the storage device can sometimes be improved.

[0158] Here, Figure 2A shows Figure 1B an enlarged view of the channel formation region and its vicinity in Figure 2B shows Figure 1C an enlarged view of the channel formation region and its vicinity in. As Figure 2A shown, the oxide semiconductor 230 has a region 231a overlapping with the conductor 242a, a region 231b overlapping with the conductor 242b, and a region 231c located between the region 231a and the region 231b. In other words, the oxide semiconductor 230 has a region 231c, and regions 231a and 231b arranged so as to sandwich the region 231c.

[0159] At least a part of region 231c overlaps with conductor 260. In addition, region 231c has a region that overlaps with opening 290. That is, region 231c has a region that overlaps with the first opening provided in insulator 280 and the second opening provided in insulator 275. In other words, insulator 280 includes the first opening in the region that overlaps with region 231c, and insulator 275 includes the second opening in the region that overlaps with region 231c.

[0160] Region 231c is used as the channel formation region of transistor 200. In addition, region 231a is used as one of the source region and the drain region of transistor 200, and region 231b is used as the other of the source region and the drain region of transistor 200.

[0161] When an oxide semiconductor is used for the semiconductor layer of a transistor, the channel formation region of the transistor is a high-resistance region with a low carrier concentration. Thus, the channel formation region of the transistor can be said to be i-type (intrinsic) or substantially i-type. In addition, compared with the channel formation region, the source region and the drain region of the transistor are regions with a higher carrier concentration and a lower resistance (low-resistance n-type regions).

[0162] In a transistor using an oxide semiconductor for the semiconductor layer, if there are impurities or oxygen vacancies in the channel formation region of the oxide semiconductor, the electrical characteristics are likely to vary, and sometimes the reliability is reduced. In addition, hydrogen near the oxygen vacancy forms a defect in which hydrogen enters the oxygen vacancy (hereinafter sometimes referred to as V O H), and electrons that become carriers may be generated. Therefore, when the channel formation region of the oxide semiconductor contains oxygen vacancies, the transistor easily has a normally-on characteristic (a characteristic in which a channel exists even when no voltage is applied to the gate electrode and current flows through the transistor). Therefore, in the channel formation region of the oxide semiconductor, preferably, compared with the source region and the drain region, there are fewer oxygen vacancies, less V o H, or a lower impurity concentration of hydrogen, nitrogen, metal elements, etc.

[0163] In contrast, in the source region and the drain region of the oxide semiconductor, preferably, compared with the channel formation region, there are more oxygen vacancies, more V O H, or a higher impurity concentration of hydrogen, nitrogen, metal elements, etc.

[0164] Then, it is preferable to provide an insulator containing oxygen that is released by heating (hereinafter sometimes referred to as excess oxygen) near the oxide semiconductor. By performing heat treatment after providing this insulator, oxygen can be supplied from the insulator to the channel formation region of the oxide semiconductor, and oxygen vacancies and V OH. Note that when an excessive amount of oxygen is supplied to the source region and the drain region of the oxide semiconductor, the on-state current of the transistor may decrease or the field effect mobility may decrease. Furthermore, when the amount of oxygen supplied to the source region or the drain region is uneven within the substrate surface, the electrical characteristics of the transistor may become uneven. That is, it is preferable that the source region and the drain region of the oxide semiconductor are not supplied with an excessive amount of oxygen.

[0165] Therefore, in this embodiment, it is preferable to use an insulator containing excess oxygen as an insulator in contact with the top surface and side surfaces of the region 231c, and to use an oxygen blocking insulator described in [Insulator] described later as an insulator in contact with the bottom surface of the oxide semiconductor 230 (regions 231a to 231c). In the semiconductor device described in this embodiment, the top surface and side surfaces of the region 231c are in contact with the insulator 250, and the bottom surface of the oxide semiconductor 230 is in contact with the insulator 223.

[0166] Furthermore, when an insulator containing excess oxygen is provided near the insulator 250, an insulator that easily transmits oxygen may be used as the insulator 250. With such a structure, oxygen in the insulator containing excess oxygen can be supplied to the region 231c through the insulator 250. In the semiconductor device described in this embodiment, as an insulator provided near the insulator 250, for example, the insulator 280 can be cited.

[0167] When an insulator containing excess oxygen is used as the insulator 280, an oxygen blocking insulator is preferably provided between the insulator 280 and the regions 231a and 231b. With such a structure, the amount of oxygen supplied to the source region or the drain region of the oxide semiconductor 230 can be reduced. In the semiconductor device described in this embodiment, the insulator 275 is provided between the insulator 280 and the regions 231a and 231b.

[0168] As the insulator 223 and the insulator 275, for example, silicon nitride is preferably used, more preferably silicon nitride formed by the ALD method, and further preferably silicon nitride formed by the PEALD method. In this case, the insulator 223 and the insulator 275 both contain silicon and nitrogen. The ALD method has good step coverage and thickness uniformity, so it is suitable for depositing thin films, covering surfaces with high aspect ratios, etc.

[0169] For example, when a silicon nitride film is deposited by PEALD, a precursor containing halogen such as fluorine, chlorine, bromine, or iodine is preferably used. 2 、N 2 O、NH 3 ,NO,NO 2 and N 2 O2 Under the atmosphere of an equal nitriding agent, plasma treatment is carried out, whereby a high-quality silicon nitride film can be deposited.

[0170] As Figure 1D shown, the insulator 275 has a structure in contact with a part of the top surface of the insulator 223. At this time, both the region 231a and the region 231b are surrounded by the insulator 223 and the insulator 275. In addition, both the region 231a and the region 231b are in contact with the insulator 223 and the insulator 275.

[0171] In addition, as Figure 1C shown, the insulator 250 is in contact with the side surface of the insulator 223 and a part of the top surface of the insulator 222. At this time, the region 231c is surrounded by the insulator 223 and the insulator 250. In addition, the region 231c is in contact with the insulator 223 and the insulator 250.

[0172] In this specification and the like, the structure that the structure body is surrounded by the first insulator and the second insulator means that the first insulator is located at least a part of the top surface and at least a part of the side surface of the structure body and the second insulator is located at least a part of the bottom surface of the structure body. Or, it means that the first insulator is located at least a part of the top surface of the structure body and the second insulator is located at least a part of the side surface and at least a part of the bottom surface of the structure body. In addition, other structures may be provided between the first insulator and the structure body. In addition, other structures may be provided between the second insulator and the structure body.

[0173] Figure 2A And Figure 2B The arrows shown in and are to visualize the case where oxygen contained in the insulator 280 diffuses through the insulator 250 into the region 231c.

[0174] In addition, in the present embodiment, it is preferable to perform microwave treatment in an oxygen-containing atmosphere in a state where the conductors 242a and 242b are provided on the oxide semiconductor 230.

[0175] In this specification and the like, microwave treatment means a treatment using a device including a power source that generates high-density plasma with microwaves. In addition, in this specification and the like, microwaves refer to electromagnetic waves having a frequency of 300 MHz or more and 300 GHz or less. Microwave treatment may also be referred to as microwave-excited high-density plasma treatment.

[0176] By performing microwave treatment in an oxygen-containing atmosphere, oxygen gas can be plasmaized using high frequencies such as microwaves or RF (Radio Frequency) and the oxygen plasma can act. At this time, high frequencies such as microwaves or RF may also be irradiated to the region 231c. By the action of plasma, microwaves, etc., the V of the region 231c OH is separated into an oxygen vacancy (V O ), and hydrogen (H). The hydrogen can be removed from region 231c and the oxygen vacancy can be filled with oxygen. Thus, the hydrogen concentration, oxygen vacancy, and V O H in region 231c can be reduced, thereby reducing the carrier concentration.

[0177] In addition, when microwave treatment is performed in an oxygen-containing atmosphere, the effects of high-frequency waves such as microwaves or RF, and oxygen plasma are shielded by the conductors 242a and 242b and do not affect regions 231a and 231b. Furthermore, the effect of oxygen plasma can be reduced by the insulators 275 and 280 provided so as to cover the oxide semiconductor 230, the conductor 242a, and the conductor 242b. Thus, during microwave treatment, the reduction of V O H and the supply of an excessive amount of oxygen do not occur in regions 231a and 231b, and thus a reduction in the carrier concentration can be prevented.

[0178] In addition, it is preferable to perform microwave treatment in an oxygen-containing atmosphere after depositing the insulating film that will become the insulator 250. Thus, by performing microwave treatment through the insulator 250 in an oxygen-containing atmosphere, oxygen can be efficiently injected into region 231c. In addition, by disposing the insulator 250 in contact with the side surfaces of the conductor 242a, the conductor 242b, and the surface of region 231c, unnecessary oxygen injection into region 231c can be suppressed, and thus oxidation of the side surfaces of the conductor 242a and the conductor 242b can be suppressed.

[0179] In addition, as the oxygen injected into region 231c, there are various forms such as oxygen atoms, oxygen molecules, oxygen ions (charged oxygen atoms or oxygen molecules), and oxygen radicals (oxygen atoms, oxygen molecules, or oxygen ions containing unpaired electrons). The oxygen injected into region 231c can be one or more of the above forms, and oxygen radicals are particularly preferred. In addition, since the film quality of the insulator 250 can be improved, the reliability of the transistor 200 is improved.

[0180] As described above, oxygen vacancies and V O H can be selectively removed in region 231c used as a channel formation region to make region 231c an i-type or substantially i-type. And, the supply of excessive oxygen to regions 231a and 231b used as source regions or drain regions can be suppressed, and the state of the n-type regions before microwave treatment can be maintained. Thus, variations in the electrical characteristics of the transistor 200 can be suppressed, and non-uniformity in the electrical characteristics of the transistor 200 within the substrate surface can be suppressed.

[0181] By adopting the above structure, as Figure 2A and Figure 2BAs shown, oxygen can be efficiently supplied to region 231c, so that the channel formation region can be made into an i-type region. Furthermore, since the amount of oxygen supplied to region 231a and region 231b is less than that to region 231c, a decrease in the carrier concentration in the source region and the drain region can be prevented.

[0182] In addition, as the insulators 223 and 275, a hydrogen-blocking insulator described in [Insulator] to be described later is preferably used. By adopting such a structure, hydrogen contained in a structure provided below the insulator 223 or a structure provided above the insulator 275 can be suppressed from mixing into the oxide semiconductor 230. Since silicon nitride has hydrogen-blocking properties, it can be applied to the insulator 275 and the insulator 223.

[0183] The silicon nitride that can be used for the insulator 223 and the insulator 275 has oxygen-blocking properties when the thickness is, for example, 1.0 nm or more, and has high oxygen-blocking properties when the thickness is, for example, 1.4 nm or more. In addition, the silicon nitride has hydrogen-blocking properties when the thickness is, for example, 2.5 nm or more, and has high hydrogen-blocking properties when the thickness is, for example, 3.3 nm or more.

[0184] Since the insulator 223 preferably has at least oxygen-blocking properties, the thickness of the insulator 223 is preferably 1.0 nm or more, more preferably 1.4 nm or more. Note that there is no particular limitation on the upper limit value of the thickness of the insulator 223, but from the viewpoints of miniaturization or high integration of the semiconductor device and improvement of the productivity of the semiconductor device, the upper limit value is preferably 20 nm or less, 10 nm or less, or 5.0 nm or less. Therefore, the insulator 223 preferably has a region with a thickness of 1.0 nm or more and 10 nm or less, and more preferably has a region with a thickness of 1.0 nm or more and 5.0 nm or less. In addition, the insulator 223 preferably has a region with a thickness of 1.4 nm or more and 10 nm or less, and more preferably has a region with a thickness of 1.4 nm or more and 5.0 nm or less.

[0185] When the insulators 223 and 275 are formed of the same insulating material, when the second opening is formed by etching the insulator 275, a third opening is formed in the insulator 223. At this time, in the third opening, the insulator 250 is in contact with the insulator 222 (see Figure 1C ).

[0186] The insulators that can be used as insulator 223 and insulator 275 are not limited to silicon nitride. For example, alumina or hafnium oxide can also be used. In addition, insulator 223 and insulator 275 can also have a stacked structure. For example, a stacked structure of silicon nitride and alumina on the silicon nitride can be used as insulator 223, and a stacked structure of alumina and silicon nitride on the alumina can be used as insulator 275. Or, a stacked structure of alumina and silicon nitride on the alumina can be used as insulator 223, and a stacked structure of silicon nitride and alumina on the silicon nitride can be used as insulator 275.

[0187] The oxide semiconductor 230 preferably has crystallinity. Examples of the oxide semiconductor having crystallinity include CAAC-OS (c-axis aligned crystalline oxide semiconductor), nc-OS (nanocrystalline oxide semiconductor), polycrystalline oxide semiconductor, single crystal oxide semiconductor, etc. CAAC-OS or nc-OS is preferably used as the oxide semiconductor 230, and CAAC-OS is particularly preferably used.

[0188] CAAC-OS has a dense structure with high crystallinity and is a metal oxide with few impurities and defects (for example, oxygen vacancies, etc.). In particular, by performing heat treatment at a temperature at which the metal oxide is not polycrystallized (for example, 400 °C or higher and 600 °C or lower) after forming the metal oxide, CAAC-OS can have a denser structure with higher crystallinity. Thus, by further increasing the density of CAAC-OS, the diffusion of impurities or oxygen in the CAAC-OS can be further reduced.

[0189] In addition, distinct grain boundaries are not easily observed in CAAC-OS, so a decrease in electron mobility due to grain boundaries is not likely to occur. Therefore, the physical properties of the metal oxide containing CAAC-OS are stable. Therefore, the metal oxide having CAAC-OS has heat resistance and high reliability.

[0190] In addition, when a crystalline oxide such as CAAC-OS is used as the oxide semiconductor 230, oxygen extraction from the oxide semiconductor 230 by the source electrode or the drain electrode can be suppressed. Therefore, even when heat treatment is performed, oxygen extraction from the oxide semiconductor 230 can be suppressed, so the transistor 200 is very stable with respect to high temperatures (so-called thermal budget) in the manufacturing process.

[0191] Here, Figure 3A and Figure 3B show Figure 1CAn enlarged view of the channel formation region and its vicinity.

[0192] CAAC-OS has a plurality of crystals, and each of the plurality of crystals has a crystal structure in which a plurality of layers are stacked. The c-axis of the crystals included in the CAAC-OS used as the oxide semiconductor 230 is preferably oriented in a direction perpendicular to the channel length direction. In addition, the c-axis of the crystals included in the region 231c used as the channel formation region is preferably oriented in a direction perpendicular to the channel length direction. By adopting such a structure, the layers included in the crystals extend in the channel length direction of the transistor 200, so that the on-state current of the transistor 200 can be increased.

[0193] In particular, it can be said that in Figures 1A to 1D In the semiconductor device shown, the channel formation region is electrically surrounded by the electric field of the conductor 260. Therefore, the side surface of the region 231c is also used as the channel formation region. Thus, it is preferable that the c-axis is also oriented in a direction perpendicular to the channel length direction in the crystals near the side surface of the region 231c facing the insulator 250. In other words, it is preferable that the side surface of the region 231c near the insulator 250 includes crystals whose c-axis is oriented in a direction perpendicular to the channel length direction.

[0194] As an example of the above structure, a structure in which the layers included in the crystals extend in a parallel or substantially parallel manner to the formation surface of the oxide semiconductor 230 can be cited (refer to Figure 3A ). By forming the above crystals when depositing the oxide semiconductor film that will become the oxide semiconductor 230, the oxide semiconductor 230 including the crystals can be formed. For example, it is preferable to deposit the oxide semiconductor film while heating the substrate. In addition, since the oxide semiconductor film deposited by the sputtering method easily has crystallinity, it is suitable for forming the oxide semiconductor 230 including the crystals.

[0195] In addition, as another example of the above structure, a structure in which the layers included in the crystals extend in a parallel or substantially parallel manner to the surface (top surface or side surface) of the oxide semiconductor 230 can be cited (refer to Figure 3B)。In addition, the oxide semiconductor 230 including the above crystals can be formed by a process performed after processing the oxide semiconductor film that will become the oxide semiconductor 230 into an island shape. For example, it is preferable that after depositing an oxide semiconductor film with low crystallinity and processing it into an island shape, one or more processes selected from plasma processing, microwave processing, and heat treatment are performed so that the oxide semiconductor 230 includes crystals. Note that when depositing an oxide semiconductor film using the ALD method, impurities contained in raw materials such as precursors sometimes remain, so the crystallinity of the oxide semiconductor film is low. Thus, by performing the above process after depositing the oxide semiconductor film and processing it into an island shape, the impurity concentration of the oxide semiconductor 230 can be reduced, and crystal growth from the surface side of the oxide semiconductor 230 can be promoted.

[0196] Note that there is no particular limitation on the method of depositing the oxide semiconductor film that will become the oxide semiconductor 230. For example, the oxide semiconductor film can be deposited using the CVD method, MBE method, PLD method, etc. In addition, the structure shown can be formed using the ALD method Figure 3A or the structure shown can be formed using the sputtering method. Figure 3B shown.

[0197] The crystallinity of the oxide semiconductor 230 can be analyzed by, for example, X-ray diffraction (XRD: X-Ray Diffraction), transmission electron microscope (TEM: Transmission Electron Microscope), or electron diffraction (ED: Electron Diffraction). Alternatively, it can also be analyzed by combining multiple of the above methods.

[0198] Note that in Figure 1B and Figure 1C the structure in which the oxide semiconductor 230 is a single layer is shown, but the present invention is not limited thereto. The oxide semiconductor 230 can also have a stacked structure of multiple oxide layers with different chemical compositions. For example, various metal oxides selected from the above metal oxides and the metal oxides described in [metal oxide] to be described later can be appropriately stacked.

[0199] For example, as Figures 4A to 4D shown, the oxide semiconductor 230 can have a stacked structure of an oxide semiconductor 230a, an oxide semiconductor 230b on the oxide semiconductor 230a, and an oxide semiconductor 230c on the oxide semiconductor 230b.

[0200] The atomic number ratio of element M to In in the metal oxide for the oxide semiconductor 230a is preferably greater than the atomic number ratio of element M to In in the metal oxide for the oxide semiconductor 230b. By adopting such a structure, diffusion of impurities and oxygen from the structure formed under the oxide semiconductor 230a to the oxide semiconductor 230b can be suppressed. In addition, diffusion of elements in the insulator 223 into the oxide semiconductor 230b can be suppressed.

[0201] For example, when the thickness of the insulator 223 is small, the effect of the insulator 223 in suppressing hydrogen diffusion is sometimes low. In this case, by providing the oxide semiconductor 230a between the insulator 223 and the oxide semiconductor 230b, diffusion of hydrogen from the substrate side to the oxide semiconductor 230b can be suppressed.

[0202] Note that when the effect of the insulator 223 in suppressing hydrogen and oxygen diffusion is high, the oxide semiconductor 230a may not be provided. For example, when the thickness of the insulator 223 is 2.5 nm or more, preferably 3.3 nm or more, the oxide semiconductor 230a may not be provided. At this time, the oxide semiconductor 230 may also have a stacked structure of the oxide semiconductor 230b and the oxide semiconductor 230c on the oxide semiconductor 230b. Note that depending on the structure of the insulator 222, the thickness of the insulator 223 is not limited to the above thickness. Even when the thickness of the insulator 223 is 1.0 nm or more or 1.4 nm or more and 2.5 nm or less, sometimes the oxide semiconductor 230a may not be provided.

[0203] In addition, for example, when depositing an oxide semiconductor film by a formation method that causes less damage to the insulator 223, the oxide semiconductor 230a may not be provided. For example, when depositing an oxide semiconductor film that will become the oxide semiconductor 230b by the ALD method or the CVD method, the oxide semiconductor 230a may not be provided. When depositing an oxide semiconductor film by the ALD method or the CVD method, damage to the insulator 223 is reduced, and diffusion of elements in the insulator 223 into the oxide semiconductor film can be suppressed.

[0204] Note that when the composition of the oxide semiconductor 230a is different from the composition of the oxide semiconductor 230b, the conductivity of the material for the oxide semiconductor 230b is sometimes different from the conductivity of the material for the oxide semiconductor 230a. In addition, the bandgap of the material for the oxide semiconductor 230b is sometimes different from the bandgap of the material for the oxide semiconductor 230a.

[0205] The conductivity of the material for the oxide semiconductor 230b is preferably different from that of the material for the oxide semiconductor 230c. For example, a material with a higher conductivity than that of the oxide semiconductor 230c can be used for the oxide semiconductor 230b. By using a material with a higher conductivity for the oxide semiconductor 230b, a transistor with a large on-state current can be realized.

[0206] Note that a material with a higher conductivity than that of the oxide semiconductor 230a can be used for the oxide semiconductor 230b. By using a material with a higher conductivity for the oxide semiconductor 230b, a transistor with a large on-state current can be realized.

[0207] In order to realize the above structure, for example, the atomic number ratio of In to Zn in the oxide semiconductor 230b is preferably greater than the atomic number ratio of In to Zn in the oxide semiconductor 230a. In addition, the atomic number ratio of In to Zn in the oxide semiconductor 230b is preferably greater than the atomic number ratio of In to Zn in the oxide semiconductor 230c. Alternatively, for example, the thickness of the oxide semiconductor 230b is preferably greater than the thicknesses of the oxide semiconductor 230a and the oxide semiconductor 230c.

[0208] Here, when a material with a higher conductivity than that of the oxide semiconductor 230c is used for the oxide semiconductor 230c provided on the side of the conductor 260 serving as the gate electrode, sometimes the threshold voltage of the transistor 200 drifts, so that the drain current flowing when the gate voltage is 0V (hereinafter, also referred to as the cutoff current) becomes large. Specifically, in the case where the transistor 200 is an n-channel transistor, the threshold voltage sometimes decreases. Therefore, a material with a lower conductivity than that of the oxide semiconductor 230b is preferably used for the oxide semiconductor 230c. Thereby, in the case where the transistor 200 is an n-channel transistor, the threshold voltage can be increased, and a transistor with a small cutoff current can be realized. Note that a small cutoff current is sometimes referred to as normally off.

[0209] By using a material with a higher conductivity than that of the oxide semiconductor 230c for the oxide semiconductor 230b as described above, a normally off and large on-state current transistor can be realized. Thereby, a low-power and high-performance semiconductor device can be realized.

[0210] In addition, the carrier concentration of the oxide semiconductor 230b is preferably higher than the carrier concentration of the oxide semiconductor 230c. By increasing the carrier concentration of the oxide semiconductor 230b, the conductivity becomes higher, and thereby a transistor with a large on-state current can be realized. By reducing the carrier concentration of the oxide semiconductor 230c, the conductivity becomes lower, and thereby a normally off transistor can be realized.

[0211] Here, although an example is shown in which a material having a higher conductivity than that of the oxide semiconductor 230c is used for the oxide semiconductor 230b, one aspect of the present invention is not limited thereto. The oxide semiconductor 230b may also use a material having a lower conductivity than that of the oxide semiconductor 230c. The carrier concentration of the oxide semiconductor 230b may be lower than the carrier concentration of the oxide semiconductor 230c.

[0212] The bandgap of the first metal oxide used for the oxide semiconductor 230b is preferably different from the bandgap of the second metal oxide used for the oxide semiconductor 230c. For example, the difference between the bandgap of the first metal oxide and the bandgap of the second metal oxide is preferably 0.1 eV or more, more preferably 0.2 eV or more, and further preferably 0.3 eV or more.

[0213] The bandgap of the first metal oxide used for the oxide semiconductor 230b may be smaller than the bandgap of the second metal oxide used for the oxide semiconductor 230c. By adopting such a structure, a transistor with a large on-state current can be achieved. In addition, when the transistor 200 is an n-channel transistor, the threshold voltage can be increased, thereby achieving a normally-off transistor.

[0214] Here, an example is shown in which the bandgap of the first metal oxide is smaller than the bandgap of the second metal oxide, but the present invention is not limited thereto. The bandgap of the first metal oxide may be larger than the bandgap of the second metal oxide.

[0215] In addition, the oxide semiconductor 230c preferably has a higher oxygen barrier property than the oxide semiconductor 230b. By disposing the oxide semiconductor 230c between the conductor 242a and the oxide semiconductor 230b and between the conductor 242b and the oxide semiconductor 230b, oxidation of the conductor 242a and the conductor 242b caused by oxygen in the oxide semiconductor 230b can be suppressed, so that the resistivity increases and the on-state current decreases. Therefore, the electrical characteristics, field-effect mobility, and reliability of the transistor 200 can be improved.

[0216] For example, when the oxide semiconductor 230a has the above three-layer stacked structure, a metal oxide having a composition of In:Ga:Zn = 1:1:1 [atomic ratio] or near it can be used as the oxide semiconductor 230a, and a metal oxide having a composition of In:Zn = 1:1 [atomic ratio] or near it or a metal oxide having a composition of In:Zn = 4:1 [atomic ratio] or near it can be used as the oxide semiconductor 230b, and a metal oxide having a composition of In:Ga:Zn = 1:1:1 [atomic ratio] or near it can be used as the oxide semiconductor 230c. By adopting this structure, the on-state current of the transistor 200 can be increased, and a transistor structure with less non-uniformity and high reliability can be achieved.

[0217] Note that when the compositions and thicknesses of the oxide semiconductors 230a and 230b are appropriately set to obtain the characteristics required for the transistor 200, the oxide semiconductor 230c may not be provided. In this case, the oxide semiconductor 230 may also have a stacked structure of the oxide semiconductor 230a and the oxide semiconductor 230b on the oxide semiconductor 230a.

[0218] As the insulator 250, a single layer or a stack of insulators described in [Insulator] to be described later can be used. As the insulator 250, for example, silicon oxide or silicon oxynitride can be used. Silicon oxide and silicon oxynitride have thermal stability, so they are preferred.

[0219] In addition, as the insulator 250, a material with a high relative dielectric constant, so-called high-k material, described in [Insulator] to be described later can also be used. For example, hafnium oxide or aluminum oxide can also be used.

[0220] The insulator 250 and the conductor 260 are provided together in the opening formed in the insulator 280 or the like. In order to miniaturize the transistor 200, the thickness of the insulator 250 is preferably small. The thickness of the insulator 250 is preferably 0.5 nm or more and 15 nm or less, more preferably 0.5 nm or more and 12 nm or less, and further preferably 0.5 nm or more and 10 nm or less. At least a part of the insulator 250 having a region with the above thickness is sufficient.

[0221] The impurity concentration of water, hydrogen, etc. in the insulator 250 is preferably reduced. Thereby, the mixing of impurities such as water and hydrogen into the channel formation region of the oxide semiconductor 230 can be suppressed.

[0222] Note that in Figure 1B and Figure 1C a single-layer insulator 250 is shown, but the present invention is not limited thereto. The insulator 250 may also have a stacked structure. For example, as Figures 4A to 4D shown, the insulator 250 may also have a stacked structure of the insulator 250a, the insulator 250b on the insulator 250a, and the insulator 250c on the insulator 250b.

[0223] The insulator 250b is preferably made of the insulator that can be used for the insulator 250 described above.

[0224] The insulator 250a preferably uses an oxygen barrier insulator described in [Insulator] which will be described later. The insulator 250a has a region in contact with the oxide semiconductor 230. When the insulator 250a has oxygen barrier properties, it is possible to suppress the detachment of oxygen from the oxide semiconductor 230 during heat treatment or the like. Therefore, it is possible to suppress the formation of oxygen vacancies in the oxide semiconductor 230. Thereby, the electrical characteristics of the transistor 200 can be improved and the reliability can be enhanced. As the insulator 250a, for example, alumina is preferably used. In this case, the insulator 250a contains at least oxygen and aluminum.

[0225] The insulator 250c preferably uses a hydrogen barrier insulator described in [Insulator] which will be described later. Thereby, it is possible to suppress the diffusion of impurities contained in the conductor 260 into the oxide semiconductor 230. Since silicon nitride has high hydrogen barrier properties, it is preferably used for the insulator 250c. In this case, the insulator 250c contains at least nitrogen and silicon.

[0226] The insulator 250c may also have oxygen barrier properties. The insulator 250c is provided between the insulator 250b and the conductor 260. Thereby, it is possible to prevent oxygen contained in the insulator 250b from diffusing into the conductor 260 and suppress the oxidation of the conductor 260. In addition, it is possible to suppress a decrease in the amount of oxygen supplied to the region 231c.

[0227] In addition, an insulator may be provided between the insulator 250b and the insulator 250c. This insulator preferably uses an insulator having a function of capturing or fixing hydrogen described in [Insulator] which will be described later. By providing this insulator, it is possible to more efficiently capture or fix hydrogen contained in the oxide semiconductor 230. Therefore, the hydrogen concentration in the oxide semiconductor 230 can be reduced. As this insulator, for example, hafnium oxide is preferably used. In this case, this insulator contains at least oxygen and hafnium. In addition, this insulator may also have an amorphous structure.

[0228] In order to miniaturize the transistor 200, the thicknesses of the insulators 250a to 250c are preferably small, and it is preferable to set their thicknesses within the above ranges. Typically, the thicknesses of the insulator 250a, the insulator 250b, the insulator having a function of capturing or fixing hydrogen, and the insulator 250c are set to 1 nm, 2 nm, 2 nm, and 1 nm, respectively. By adopting such a structure, good electrical characteristics can also be obtained when the transistor 200 is miniaturized or highly integrated.

[0229] In order to reduce the thicknesses of the insulators 250a to 250c as described above, it is preferable to perform deposition using the ALD method. In addition, in order to provide the insulators 250a to 250c inside the openings of the insulator 280 or the like, it is preferable to perform deposition using the ALD method.

[0230] In Figures 4A to 4D the insulator 250 has a stacked structure of three layers, namely insulator 250a to insulator 250c, but the present invention is not limited thereto. The insulator 250 may also have a stacked structure of two layers or four or more layers. At this time, each layer included in the insulator 250 is preferably appropriately selected from insulator 250a to insulator 250c and an insulator having a function of capturing or fixing hydrogen.

[0231] The insulator 280 is used as an interlayer film, so its relative dielectric constant is preferably low. By using a material with a low relative dielectric constant for the interlayer film, the parasitic capacitance generated between wirings can be reduced. As the insulator 280, a single layer or a stack of insulators containing a material with a low relative dielectric constant described in [Insulator] to be described later can be used. Silicon oxide and silicon oxynitride have thermal stability, so they are preferred.

[0232] In addition, the concentration of impurities such as water and hydrogen in the insulator 280 is preferably reduced. Thereby, the mixing of impurities such as water and hydrogen into the channel formation region of the oxide semiconductor 230 can be suppressed.

[0233] The insulator 283 is preferably a hydrogen barrier insulator described in [Insulator] to be described later. Thereby, the diffusion of hydrogen from the outside of the transistor 200 through the insulator 250 to the oxide semiconductor 230 can be suppressed. Since both silicon nitride and silicon oxynitride have the characteristics of less release of impurities (such as water and hydrogen) from themselves and being less permeable to oxygen and hydrogen, they can be applied to the insulator 283.

[0234] Particularly preferably, silicon nitride deposited by a sputtering method is used as the insulator 283. At this time, the insulator 283 contains silicon and nitrogen. The sputtering method does not require the use of a molecule containing hydrogen as a deposition gas, so the hydrogen concentration of the insulator 283 can be reduced. In addition, by depositing the insulator 283 using the sputtering method, a silicon nitride with a high density can be formed.

[0235] The thickness of the insulator 223 may also be different from the thickness of the insulator 283. For example, the thickness of the insulator 223 is preferably smaller than the thickness of the insulator 283. It is sufficient that at least a part of the insulator 223 has a region with a thickness smaller than that of the insulator 283. As described above, the insulator 223 preferably has at least oxygen barrier properties, and the insulator 283 preferably has hydrogen barrier properties. Therefore, the insulator 223 may also have a region with a thickness smaller than that of the insulator 283.

[0236] The concentration of impurity elements in the insulator 223 can also be different from the concentration of impurity elements in the insulator 283. For example, the concentration of impurity elements in the insulator 223 is sometimes higher than the concentration of impurity elements in the insulator 283. Note that the impurity elements are halogens such as fluorine, chlorine, bromine, iodine, etc., hydrogen, or carbon. As described above, the insulator 223 is preferably deposited by the ALD method, and the insulator 283 is preferably deposited by the sputtering method. When depositing an insulator by the ALD method, impurities contained in raw materials such as precursors remain. Therefore, an insulator deposited by the ALD method tends to have a high concentration of impurity elements. For example, when using a precursor containing a halogen such as fluorine, chlorine, bromine, iodine, etc., an insulator deposited by the ALD method tends to have a high halogen concentration. That is, the halogen concentration in the insulator 223 is sometimes higher than the halogen concentration in the insulator 283. Additionally, for example, when using a precursor formed of an organic substance (hereinafter referred to as an organic precursor), an insulator deposited by the ALD method tends to have a high hydrogen concentration and a high carbon concentration. That is, the hydrogen concentration in the insulator 223 is sometimes higher than the hydrogen concentration in the insulator 283. Furthermore, the carbon concentration in the insulator 223 is sometimes higher than the carbon concentration in the insulator 283.

[0237] The insulator 222 is preferably a hydrogen-blocking insulator described in [Insulator] which will be described later. When the insulator 222 has hydrogen-blocking properties, even if the thickness of the insulator 223 is reduced, diffusion of hydrogen from below the insulator 222 to the oxide semiconductor 230 can be suppressed.

[0238] Additionally, as the insulator 222, a metal oxide having an amorphous structure is preferably used. By adopting such a structure, hydrogen in the channel formation region of the transistor 200 can be captured or fixed.

[0239] Note that the insulator 222 can also have oxygen-blocking properties. By providing the insulator 222 and the insulator 223 having oxygen-blocking properties, detachment of oxygen from the oxide semiconductor 230 can be suppressed.

[0240] As the insulator 222, an insulator preferably selected as an etch stop film when etching the insulator 223 to form the third opening is used.

[0241] Note that in Figure 1B and Figure 1C a structure in which the insulator 222 is a single layer is shown, but the present invention is not limited thereto. The insulator 222 can also have a stacked structure. As an example, a stacked structure of silicon nitride and hafnium oxide on the silicon nitride can also be adopted. By adopting such a structure, diffusion of hydrogen from below the insulator 222 to the oxide semiconductor 230 can be suppressed.

[0242] As the conductor 260, a single layer or a stack of the conductors described in [Conductor] which will be described later can be used. As the conductor 260, for example, a highly conductive material such as tungsten can be used.

[0243] In addition, as the conductor 260, it is preferable to use a conductive material that is not easily oxidized or a conductive material having a function of suppressing oxygen diffusion. As such a conductive material, a conductive material containing nitrogen (for example, titanium nitride or tantalum nitride, etc.) and a conductive material containing oxygen (for example, ruthenium oxide, etc.) can be cited. When a conductive material containing metal and nitrogen is used as the conductor 260, the conductor 260 contains at least metal and nitrogen. Thereby, a decrease in the conductivity of the conductor 260 can be suppressed.

[0244] Note that, Figure 1B and Figure 1C show a single-layer conductor 260, but the present invention is not limited thereto. The conductor 260 may also have a stacked structure. For example, as shown in Figure 4B and Figure 4C , the conductor 260 may also have a stacked structure of a conductor 260a and a conductor 260b on the conductor 260a.

[0245] As the conductor 260a, it is preferable to use a conductive material having a function of suppressing oxygen diffusion. Thereby, oxidation of the conductor 260b by oxygen in the insulator 280 etc. can be suppressed, resulting in a decrease in conductivity. For example, titanium nitride can be used for the conductor 260a.

[0246] The conductor 260b is preferably a highly conductive material. For example, tungsten can be used as the conductor 260b. By providing a layer containing tungsten in this way, the conductivity of the conductor 260 can be improved, enabling the conductor 260 to fully function as a wiring.

[0247] In Figure 4B and Figure 4C , the conductor 260 has a stacked structure of two layers, namely the conductor 260a and the conductor 260b, but the present invention is not limited thereto. The conductor 260 may also have a stacked structure of three or more layers.

[0248] As the conductor 260a and the conductor 260b, a single layer or a stack of the conductors described in [Conductor] which will be described later can be used. As the conductor 260a and the conductor 260b, a highly conductive material such as tungsten can be used.

[0249] Similar to the conductor 260, the conductors 242a and 242b are preferably made of a conductive material that is not easily oxidized or a conductive material having a function of suppressing oxygen diffusion, etc. For example, titanium nitride or tantalum nitride can be used. At this time, both the conductor 242a and the conductor 242b contain at least metal and nitrogen. By adopting such a structure, over-oxidation of the conductors 242a and 242b due to the oxide semiconductor 230 can be suppressed.

[0250] Note that in Figure 1B and Figure 1C the conductors 242a and 242b are both single-layer, but the present invention is not limited thereto. The conductors 242a and 242b may also have a laminated structure. For example, as shown in Figure 4B and Figure 4C the conductor 242a may also have a laminated structure of a conductor 242a1 and a conductor 242a2 on the conductor 242a1. The conductor 242b may also have a laminated structure of a conductor 242b1 and a conductor 242b2 on the conductor 242b1. At this time, for example, titanium nitride or tantalum nitride can be used as the conductor 242a1 and the conductor 242b1, and tungsten can be used as the conductor 242a2 and the conductor 242b2. By providing a layer containing tungsten in this way, the conductivity of the conductors 242a and 242b can be improved and their function as wiring can be fully exerted.

[0251] Note that in Figure 1B and Figure 1D an insulator 275 is provided in contact with the top surfaces of the conductor 242a and the conductor 242b, but the present invention is not limited thereto. For example, as shown in Figure 4B and Figure 4D an insulator 271a may also be provided between the conductor 242a and the insulator 275, and an insulator 271b may be provided between the conductor 242b and the insulator 275.

[0252] Both the insulator 271a and the insulator 271b are used as an etch stop layer for protecting the conductors 242a and 242b. Therefore, as shown in Figure 4B and Figure 4D in the cross-section of the transistor 200, preferably, the side ends of the insulator 271a coincide with the side ends of the conductor 242a, and the side ends of the insulator 271b coincide with the side ends of the conductor 242b.

[0253] The insulators 271a and 271b are preferably inorganic insulators that are not easily oxidized by the conductors 242a and 242b because they are in contact with the conductors 242a and 242b, respectively. For example, as the insulators 271a and 271b, insulators that can be used for the insulator 275 are preferably used.

[0254] Note that Figure 4B and Figure 4D show a structure in which both the insulators 271a and 271b are single layers, but the present invention is not limited thereto. The insulators 271a and 271b may also both have a laminated structure.

[0255] In Figures 1B to 1D , the insulator 283 is provided in contact with the top surface of the insulator 280, the top surface of the insulator 250, and the top surface of the conductor 260, but the present invention is not limited thereto. For example, as shown in Figures 4B to 4D , an insulator 282 may also be provided between the insulator 283 and the insulator 280, the insulator 250, and the conductor 260.

[0256] As the insulator 282, an insulator that can add oxygen to the insulator 280 is preferably used. For example, alumina is preferably used as the insulator 282. In this case, the insulator 282 contains at least oxygen and aluminum. In addition, the insulator 282 or the insulating film that will become the insulator 282 is preferably deposited by a sputtering method, and more preferably deposited by a sputtering method in an oxygen-containing atmosphere. By depositing the insulator 282 by a sputtering method in an oxygen-containing atmosphere, oxygen can be added to the insulator 280 while depositing. Thereby, the insulator 280 can contain excess oxygen.

[0257] Here, as the insulator 282, a metal oxide having an amorphous structure is preferably used. A metal oxide having an amorphous structure sometimes has the following property: oxygen atoms having dangling bonds exist and hydrogen is captured or fixed by the dangling bonds. By using the above metal oxide having an amorphous structure as a component of the transistor 200 or disposing it around the transistor 200, hydrogen contained in the transistor 200 can be captured or fixed. In particular, it is preferable to capture or fix hydrogen contained in the channel formation region of the transistor 200. By adopting such a structure, a transistor 200 having good characteristics and high reliability can be manufactured.

[0258] In addition, the insulator 282 preferably has an amorphous structure, but a region having a polycrystalline structure may be formed in a part thereof. Also, the insulator 282 may have a multilayer structure in which a layer having an amorphous structure and a layer having a polycrystalline structure are laminated. For example, it may have a laminated structure in which a layer having a polycrystalline structure is formed on a layer having an amorphous structure.

[0259] Note that Figures 4B to 4DThe insulator 282 is shown as having a single-layer structure, but the present invention is not limited thereto. The insulator 282 may also have a stacked structure.

[0260] [Structural Example 1-2]

[0261] Although Figures 1A to 1D the transistor 200 is shown as having a single-gate structure including one gate, the present invention is not limited to this structure. For example, the transistor 200 may also include a back gate.

[0262] Referring to Figures 5A to 5D Another example of the structure of the semiconductor device will be described. Figures 5A to 5D are a plan view and a cross-sectional view of the semiconductor device. Figures 5A to 5D The semiconductor device shown mainly differs from the Figures 1A to 1D semiconductor device shown in that it includes a conductor 215 and an insulator 216. The following mainly describes the parts different from the description of the above [Structural Example 1-1], and the description of the repeated parts will sometimes be omitted by referring to the above description.

[0263] As Figures 5A to 5D shown, an insulator 216 and a conductor 215 are provided below the insulator 222. In addition, the conductor 215 is arranged so as to be embedded in the opening formed in the insulator 216. Here, the height of the top surface of the conductor 215 is the same as the height of the top surface of the insulator 216.

[0264] In Figures 5A to 5D the transistor 200 shown, the conductor 260 is used as the first gate (also called the top gate) electrode, and the conductor 215 is used as the second gate (also called the back gate) electrode. In addition, the insulator 250 is used as the first gate insulator, and a part of the insulator 222 and a part of the insulator 223 are used as the second gate insulator. Therefore, it can be said that the transistor 200 also includes the conductor 215 and the insulator 222.

[0265] The conductor 215 has a region overlapping the conductor 260 with the insulators 222, 223, the oxide semiconductor 230, and the insulator 250 therebetween.

[0266] In addition, as Figure 5B shown, the conductor 215 is preferably larger than the region in the oxide semiconductor 230 that does not overlap with the conductors 242a and 242b. In addition, as Figure 5CAs shown, the conductor 215 preferably extends to a region outside the end portion in the channel width direction of the oxide semiconductor 230. That is, preferably, outside the side surface in the channel width direction of the oxide semiconductor 230, the conductor 215 overlaps with the conductor 260 with an insulator therebetween. By having the above structure, the channel formation region of the oxide semiconductor 230 can be electrically surrounded by the electric field of the conductor 260 serving as the first gate electrode and the electric field of the conductor 215 serving as the second gate electrode.

[0267] Note that in this specification and the like, a transistor structure in which the channel formation region is at least electrically surrounded by the electric field of the first gate electrode is referred to as a surrounded channel (S-channel) structure. In addition, the S-channel structure disclosed in this specification and the like is different from the Fin type structure and the planar type structure. On the other hand, the S-channel structure disclosed in this specification and the like can be regarded as a kind of Fin type structure. In addition, in this specification and the like, the Fin type structure refers to a structure in which gate electrodes are arranged so as to surround at least two or more surfaces of the channel (specifically, two surfaces, three surfaces, four surfaces, etc.). By adopting the Fin type structure and the S-channel structure, the tolerance to the short channel effect can be improved. In other words, a transistor in which the short channel effect is not likely to occur can be realized.

[0268] By adopting the above S-channel structure as the transistor 200, the channel formation region can be electrically surrounded. Since the S-channel structure is a structure that electrically surrounds the channel formation region, it can also be said that this structure is substantially the same as the GAA (Gate All Around) structure or the LGAA (Lateral Gate All Around) structure. By making the transistor 200 have the S-channel structure, the GAA structure, or the LGAA structure, the channel formation region formed at the interface or near the interface between the oxide semiconductor 230 and the gate insulator can be regarded as the entire bulk of the oxide semiconductor 230. Therefore, the current density flowing through the transistor can be increased, and thus an increase in the on-state current of the transistor or the field effect mobility of the transistor can be expected.

[0269] In addition, as Figure 5C shown, the conductor 215 is extended to be used as a wiring. However, the present invention is not limited thereto, and a conductor used as a wiring may also be provided under the conductor 215. In addition, it is not necessarily required to provide one conductor 215 in each transistor. For example, the conductor 215 may also be shared among multiple transistors.

[0270] Figure 5BThe structure in which the conductor 215 is a single layer is shown, but the present invention is not limited thereto. For example, the conductor 215 may also have a stacked structure of two or more layers.

[0271] The conductor 215 is sometimes used as a second gate electrode. In this case, by independently changing the potential applied to the conductor 215 without linking it to the potential applied to the conductor 260, the threshold voltage (Vth) of the transistor 200 can be controlled. In particular, when a negative potential (a potential lower than the source potential) is applied to the conductor 215, the Vth of the transistor 200 can be increased and the off-state current can be reduced. Thus, compared with the case where a negative potential is not applied to the conductor 215, the drain current when the potential applied to the conductor 260 is 0 V can be reduced in the case where a negative potential is applied to the conductor 215.

[0272] In addition, the resistivity of the conductor 215 is designed in consideration of the potential applied to the conductor 215 as described above, and the thickness of the conductor 215 is set according to this resistivity. In addition, the thickness of the insulator 216 is substantially the same as the thickness of the conductor 215. Here, it is preferable to reduce the thicknesses of the conductor 215 and the insulator 216 within the range allowed by the design of the conductor 215. By reducing the thickness of the insulator 216, the absolute amount of impurities such as hydrogen contained in the insulator 216 can be reduced, so that the diffusion of such impurities into the oxide semiconductor 230 can be reduced.

[0273] Since the insulator 216 is used as an interlayer film, its relative dielectric constant is preferably low. By using a material with a low relative dielectric constant for the interlayer film, the parasitic capacitance generated between wirings can be reduced. As the insulator 216, an insulator containing a material with a low relative dielectric constant described in [Insulator] to be described later can be used in a single layer or a stacked layer. It is preferable to use silicon oxide and silicon oxynitride because they have thermal stability.

[0274] In addition, the impurity concentrations of water, hydrogen, etc. in the insulator 216 are preferably reduced. Thereby, the mixing of impurities such as water and hydrogen into the channel formation region of the oxide semiconductor 230 can be suppressed.

[0275] [Structural Examples 1-3]

[0276] In Figures 5A to 5D , the side end portion of the conductor 242a coincides with the side end portion of the oxide semiconductor 230, and the side end portion of the conductor 242b coincides with the side end portion of the oxide semiconductor 230, but the present invention is not limited to this structure. For example, the conductor 242a and the conductor 242b may also have regions in contact with the side surface of the oxide semiconductor 230.

[0277] Refer to Figures 6A to 6D to describe another example of the structure of the semiconductor device. Figures 6A to 6DIt is a plan view and a cross-sectional view of a semiconductor device including a transistor 200. Figures 6A to 6D The illustrated transistor 200 is Figures 5A to 5D The main difference from the illustrated transistor 200 lies in the shapes of the conductors 242a and 242b. The following mainly describes the parts different from the descriptions of the above [Structure Example 1-1] and [Structure Example 1-2]. For the repeated parts, refer to the above descriptions and sometimes omit the descriptions.

[0278] The conductor 242a has a region in contact with the top surface of the insulator 223 and the side surface of the oxide semiconductor 230 on the A1 side. In addition, the conductor 242b has a region in contact with the top surface of the insulator 223 and the side surface of the oxide semiconductor 230 on the A2 side. By adopting such a structure, the contact area between the oxide semiconductor 230 and the conductors 242a and 242b can be increased, thereby improving the on-state current, field-effect mobility, and frequency characteristics of the transistor 200.

[0279] The conductor 242a may also have a region extending in the channel length direction or the channel width direction of the transistor 200. At this time, the conductor 242a can also be used as a wiring. In addition, the same applies to the conductor 242b.

[0280] [Structure Example 1-4]

[0281] In Figures 5A to 5D , in the opening 290, the side surfaces of the insulator 250, the insulator 280, the insulator 275, and the insulator 223 are in contact, but the present invention is not limited to this structure. For example, in the opening 290, an insulator may also be provided between the insulator 250, the insulator 280, the insulator 275, and the insulator 223.

[0282] Refer to Figures 7A to 7D to describe another example of the structure of the semiconductor device. Figures 7A to 7D It is a plan view and a cross-sectional view of a semiconductor device including a transistor 200. Figures 7A to 7D The illustrated transistor 200 is mainly different from the Figures 5A to 5D illustrated transistor 200 in that it includes an insulator 255. In addition, Figures 7A to 7D shows a structure in which both the conductor 242a and the conductor 242b have a two-layer stacked structure. The following mainly describes the parts different from the descriptions of the above [Structure Example 1-1] and [Structure Example 1-2]. For the repeated parts, refer to the above descriptions and sometimes omit the descriptions.

[0283] The conductor 242a includes a conductor 242a1 and a conductor 242a2 on the conductor 242a1, and the conductor 242b includes a conductor 242b1 and a conductor 242b2 on the conductor 242b1.

[0284] The insulator 255 is disposed between the insulator 250 and the insulators 280, 275, and 223. Specifically, in the opening 290, the side surfaces of the insulator 250 and the insulator 280, the side surface of the insulator 250, the side surface of the conductor 242a2, the top surface of the conductor 242a1, the side surface of the conductor 242b2, the top surface of the conductor 242b1, the side surface of the insulator 223, and the top surface of the insulator 222 are in contact. In addition, the insulator 255 has an opening in the region between the conductors 242a1 and 242b1. Hereinafter, the opening provided in the insulator 255 is referred to as the fourth opening.

[0285] As Figure 7B shown, in a cross-section in the channel length direction of the transistor 200, the distance between the conductors 242a1 and 242b1 (referred to as the first distance) is smaller than the distance between the conductors 242a2 and 242b2 (referred to as the second distance). By adopting such a structure, the distance between the source and the drain can be further reduced and the channel length can be reduced accordingly. Therefore, the frequency characteristics of the transistor 200 can be improved. Thus, by realizing miniaturization of the semiconductor device, a semiconductor device with an increased operating speed can be provided.

[0286] The opening 290 overlaps with the region between the conductors 242a2 and 242b2. In addition, a part of the conductor 242a1 and a part of the conductor 242b1 are formed to protrude inwardly of the opening 290. Therefore, the insulator 255 is in contact with the top surface of the conductor 242a1, the top surface of the conductor 242b1, the side surface of the conductor 242a2, and the side surface of the conductor 242b2 inside the opening 290. In addition, the insulator 250 is in contact with the top surface of the oxide semiconductor 230 in the region between the conductors 242a1 and 242b1.

[0287] The insulator 255 is preferably an insulator that is not easily oxidized, such as a nitride. The insulator 255 is formed so as to be in contact with the side surfaces of the conductors 242a2 and 242b2, and has a function of protecting the conductors 242a2 and 242b2. Preferably, heat treatment is performed in an oxygen-containing atmosphere after separating the conductors 242a2 and 242b2 and before depositing the insulator 250. At this time, since the insulator 255 is formed so as to be in contact with the side surfaces of the conductors 242a2 and 242b2, the conductors 242a2 and 242b2 can be prevented from being excessively oxidized.

[0288] The thickness of the insulator 255 is preferably 1 nm or more and 20 nm or less, more preferably 1 nm or more and 15 nm or less, and still more preferably 3 nm or more and 10 nm or less. For example, it can be set to about 5 nm. When the insulator 255 has the above thickness, the distance between the conductor 260 and the conductor 242a or the conductor 242b can be increased to reduce the parasitic capacitance. Note that the insulator 255 only needs to have a region with a thickness of the above value in at least a part thereof.

[0289] As the insulator 255, it is preferable to use the insulator that can be used as the insulator 223 described above. As the insulator 255, for example, silicon nitride is preferably used, and silicon nitride formed by the ALD method is more preferably used. By using the ALD method, the insulator 255 can be deposited with high coverage and a relatively thin thickness on the side walls of the first opening and the second opening, and the sides of the conductors 242a2 and 242b2.

[0290] The portion of the insulator 255 disposed in the opening 290 reflects the shape of the opening 290. Therefore, the insulator 255 is provided so as to cover a part of the bottom and the side walls of the opening 290.

[0291] The portions of the insulator 250 and the conductor 260 disposed in the opening 290 and the fourth opening reflect the shapes of the opening 290 and the fourth opening. Therefore, the insulator 250 is provided so as to cover the insulator 255, the bottom and the side walls of the fourth opening, and the conductor 260 is provided so as to be embedded in the recess of the insulator 250 that reflects the shapes of the opening 290 and the fourth opening.

[0292] As Figure 7B shown, in the cross-section in the channel length direction of the transistor 200, the conductor 260 includes a first region having a first width and a second region having a second width on the first region. The first width is smaller than the second width.

[0293] [Structural Examples 1-5]

[0294] In Figures 7A to 7D it, the insulator 255 has a region located between the insulator 250 and the oxide semiconductor 230, but the present invention is not limited to this structure. For example, the insulator 255 may not have a region located between the insulator 250 and the oxide semiconductor 230.

[0295] Refer to Figures 8A to 8D to illustrate another example of the structure of the semiconductor device. Figures 8A to 8D is a plan view and a cross-sectional view of a semiconductor device including the transistor 200. Figures 8A to 8D Shown of the transistor 200 and Figures 7A to 7DThe transistor 200 shown is mainly different in the shapes of the insulator 255, the insulator 250, and the conductor 260. The following mainly describes the parts different from the descriptions of the above [Structure Examples 1-4], etc., and the descriptions of the repeated parts are sometimes omitted with reference to the above descriptions.

[0296] As shown in FIG. 8, in the cross-section in the channel length direction of the transistor 200, the distance (first distance) between the conductor 242a1 and the conductor 242b1 is smaller than the distance (second distance) between the conductor 242a2 and the conductor 242b2. Specifically, the difference between the first distance and the second distance is consistent with twice the thickness of the insulator 255. In other words, the first distance is consistent with the second distance plus twice the thickness of the insulator 255. Here, the thickness of the insulator 255 refers to the thickness in the A1-A2 direction of at least a part of the insulator 255. By adopting such a structure, the distance between the source and the drain can be further reduced and the channel length can be reduced correspondingly. Therefore, the frequency characteristics of the transistor 200 can be improved. Thus, by realizing the miniaturization of the semiconductor device, a semiconductor device with an improved operating speed can be provided.

[0297] In the cross-section in the channel length direction of the transistor 200, the side surface of the insulator 255 on the insulator 250 side is consistent with the side surface of the conductor 242a1. In addition, the side surface of the insulator 255 on the insulator 250 side is consistent with the side surface of the conductor 242b1.

[0298] The insulator 255 is formed in a sidewall shape by anisotropic etching so as to contact the sidewall of the opening 290. The insulator 255 is formed so as to contact the side surfaces of the conductor 242a2 and the conductor 242b2, and has the function of protecting the conductor 242a2 and the conductor 242b2. Note that it is preferable to perform heat treatment in an oxygen-containing atmosphere after dividing the conductor 242a1 and the conductor 242b1 and before depositing the insulator 250. At this time, since the insulator 255 is formed so as to contact the side surfaces of the conductor 242a2 and the conductor 242b2, the conductor 242a2 and the conductor 242b2 can be prevented from being over-oxidized. In addition, even if microwave treatment is performed after dividing the conductor 242a1 and the conductor 242b1, the formation of an oxide film on the side surfaces of the conductor 242a and the conductor 242b can be suppressed.

[0299] The arrangement of the insulator 250 and the conductor 260 in the opening 290 reflects the shape of the opening 290. Therefore, the insulator 250 is provided so as to cover the insulator 255, the bottom and the sidewall of the opening, and the conductor 260 is provided so as to be embedded in the recess of the insulator 250.

[0300] [Structure Examples 1-6]

[0301] In Figures 1A to 1D this structure, the oxide semiconductor 230 is disposed on the insulator 223, but the present invention is not limited to this structure. For example, an insulator may also be disposed between the insulator 223 and the oxide semiconductor 230.

[0302] Refer to Figures 9A to 9D to illustrate another example of the structure of the semiconductor device. Figures 9A to 9D are a plan view and a cross-sectional view of a semiconductor device including a transistor 200. Figures 9A to 9D The transistor 200 shown includes an insulator 225 and is mainly different from the transistor 200 shown in Figures 1A to 1D in this regard. The following mainly describes the parts different from the description of the above [Structure Example 1-1], and the description of the repeated parts will sometimes be omitted with reference to the above description.

[0303] The insulator 225 is disposed between the insulator 223 and the oxide semiconductor 230. Specifically, the insulator 225 is disposed on the insulator 223, and the oxide semiconductor 230 is disposed so as to cover the top surface and the side surfaces of the insulator 225. The oxide semiconductor 230 is in contact with the top surface and the side surfaces of the insulator 225 and the top surface of the insulator 223.

[0304] In the above structure, both the source region and the drain region are surrounded by the insulator 223 and the insulator 275 together with the insulator 225. In addition, both the source region and the drain region are in contact with the insulator 223, the insulator 225, and the insulator 275.

[0305] In addition, the channel formation region is surrounded by the insulator 223 and the insulator 250 together with the insulator 225. In addition, the channel formation region is in contact with the insulator 223, the insulator 225, and the insulator 250.

[0306] As described above, since the insulator 225 is surrounded by the insulator 223 and the insulator 275, there is no particular limitation on the material used for the insulator 225. For the insulator 225, for example, an insulating material that can be used for the insulator 222, the insulator 223, the insulator 280, or the insulator 250 may be used. In addition, since the insulator 225 has a high aspect ratio shape, it is preferably formed in a sidewall shape on the side surface of the sacrificial layer. Therefore, the insulator 225 is preferably formed by the ALD method with high coverage. For example, the insulator 225 may be formed of silicon nitride or hafnium oxide deposited by the ALD method. When silicon nitride is used as the insulator 225, the insulator 225 contains silicon and nitrogen.

[0307] The insulator 225 is formed in contact with the insulator 222. The insulator 225 is as Figure 9CAs shown, in the cross-section in the channel width direction, it has a shape with a high aspect ratio. Here, the aspect ratio of the insulator 225 in the cross-section in the channel width direction refers to the ratio of the length in the A3 - A4 direction of the insulator 225 to the length in the direction perpendicular to the formed surface of the insulator 225. Here, the length in the A3 - A4 direction of the insulator 225 can also be said to be the width of the insulator 225 or the length in the direction in which the conductor 260 of the insulator 225 extends. In addition, the formed surface of the insulator 225 is, for example, the insulator 222. In addition, the length in the direction perpendicular to the formed surface of the insulator 225 can also be said to be the height of the insulator 225.

[0308] The height of the insulator 225 is at least greater than the length in the A3 - A4 direction of the insulator 225. The height of the insulator 225 can be greater than 1 times the width of the insulator 225, preferably 2 times or more, more preferably 5 times or more, and further preferably 10 times or more. In addition, the height of the insulator 225 is preferably 20 times or less the width of the insulator 225.

[0309] The oxide semiconductor 230, the conductor 242a, and the conductor 242b are provided so as to cover such an insulator 225 with a high aspect ratio. In the transistor 200, as Figure 9C shown, the oxide semiconductor 230 is provided in a state of being folded in half with the insulator 225 sandwiched therebetween, and the insulator 250 and the conductor 260 are provided so as to cover the oxide semiconductor 230. Thus, in the cross-section in the channel width direction, the oxide semiconductor 230 and the conductor 260 are opposed to each other with the insulator 250 interposed therebetween at the top, the side surface on the A3 side, and the side surface on the A4 side of the insulator 225. That is, the oxide semiconductor 230 located at the top, the side surface on the A3 side, and the side surface on the A4 side of the insulator 225 all serve as channel formation regions. Therefore, the channel width of the transistor 200 is larger than that in the case where the insulator 225 is not provided by the portions of the oxide semiconductor 230 on the A3 side and A4 side surfaces of the insulator 225.

[0310] As described above, by increasing the channel width, the on-state current, field-effect mobility, frequency characteristics, etc. of the transistor 200 can be improved. Thereby, a semiconductor device with a high operating speed can be provided. In addition, in the above structure, by providing the insulator 225, the channel width can be increased without increasing the occupied area of the transistor 200. Thereby, miniaturization or high integration of the semiconductor device can be achieved.

[0311] As Figure 9CAs shown, the oxide semiconductor 230 is provided in a state where it sandwiches the insulator 225 and is folded in half. In the oxide semiconductor 230 in this state, the c-axis of the crystal contained in the oxide semiconductor 230 is preferably oriented in a direction perpendicular to the channel length direction. In addition, the c-axis of the crystal contained in the channel formation region is preferably oriented in a direction perpendicular to the channel length direction. By adopting such a structure, the layers included in the crystal extend in the channel length direction of the transistor 200, so that the on-state current of the transistor 200 can be increased.

[0312] In addition, as described in [Structural Example 1-1], it is preferable that the c-axis is also oriented in a direction perpendicular to the channel length direction in the crystal near the side surface of the region 231c facing the insulator 250. In other words, it is preferable that the side surface of the region 231c near the insulator 250 includes a crystal whose c-axis is oriented in a direction perpendicular to the channel length direction. At this time, in the Figure 9C structure shown, the layers included in this crystal extend in a direction parallel or substantially parallel to the surface (top surface or side surface) of the oxide semiconductor 230. In addition, the layers included in this crystal extend in a direction parallel or substantially parallel to the formed surface of the oxide semiconductor 230.

[0313] <Structural Materials of Semiconductor Devices>

[0314] Hereinafter, the constituent materials that can be used for semiconductor devices will be described.

[0315] [Substrate]

[0316] As the substrate for forming the transistor 200, for example, an insulator substrate, a semiconductor substrate, or a conductor substrate can be used. As the insulator substrate, for example, a glass substrate, a quartz substrate, a sapphire substrate, a stabilized zirconia substrate (such as a yttria-stabilized zirconia substrate), a resin substrate, etc. can be cited. In addition, as the semiconductor substrate, for example, a semiconductor substrate made of silicon, germanium, or a compound semiconductor substrate composed of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, gallium oxide, etc. can be cited. Also, a semiconductor substrate having an insulator region inside the above semiconductor substrate, such as an SOI (Silicon On Insulator) substrate, etc. can be cited. As the conductor substrate, a graphite substrate, a metal substrate, an alloy substrate, a conductive resin substrate, etc. can be cited. Or, a substrate containing a metal nitride, a substrate containing a metal oxide, etc. can be cited. In addition, an insulator substrate provided with a conductor or a semiconductor, a semiconductor substrate provided with a conductor or an insulator, a conductor substrate provided with a semiconductor or an insulator, etc. can be cited. Or, a substrate provided with elements on these substrates can also be used. As the elements provided on the substrate, a capacitor element, a resistor, a switching element, a light-emitting element, a storage element, etc. can be cited.

[0317] [Insulator]

[0318] As the insulator, there are oxides, nitrides, oxynitrides, nitrogen oxides, metal oxides, metal oxynitrides, metal nitrogen oxides, etc. having insulating properties.

[0319] For example, when miniaturizing and highly integrating transistors, due to the thinning of the gate insulator film, problems such as leakage current sometimes occur. By using a high-k material as the insulator for the gate insulator, low voltage operation of the transistor can be achieved while maintaining the physical thickness. In addition, the equivalent oxide thickness (EOT) of the insulator used as the gate insulator can be reduced. On the other hand, by using a material with a low relative dielectric constant for the insulator used as the interlayer film, the parasitic capacitance generated between the wirings can be reduced. Therefore, it is preferable to select the material according to the function of the insulator. In addition, a material with a low relative dielectric constant is also a material with a high dielectric strength.

[0320] As materials with a high relative dielectric constant (high-k), for example, alumina, gallium oxide, hafnium oxide, tantalum oxide, zirconium oxide, hafnium zirconium oxide, an oxide containing aluminum and hafnium, an oxynitride containing aluminum and hafnium, an oxide containing silicon and hafnium, an oxynitride containing silicon and hafnium, and a nitride containing silicon and hafnium can be cited.

[0321] As materials with a low relative dielectric constant, for example, inorganic insulating materials such as silicon oxide, silicon oxynitride, and silicon nitride oxide, resins such as polyester, polyolefin, polyamide (nylon, aramid, etc.), polyimide, polycarbonate, and acrylic resin can be cited. In addition, as inorganic insulating materials with a low relative dielectric constant other than the above, for example, silicon oxide added with fluorine, silicon oxide added with carbon, and silicon oxide added with carbon and nitrogen can be cited. In addition, porous silicon oxide can be cited. In addition, these silicon oxides can also contain nitrogen.

[0322] In addition, by surrounding a transistor using a metal oxide with an insulator having a function of suppressing the permeation of impurities and oxygen, the electrical characteristics of the transistor can be stabilized. As the insulator having a function of suppressing the permeation of impurities and oxygen, for example, a single layer or a laminate of an insulator containing boron, carbon, nitrogen, oxygen, fluorine, magnesium, aluminum, silicon, phosphorus, chlorine, argon, gallium, germanium, yttrium, zirconium, lanthanum, neodymium, hafnium, or tantalum can be used. Specifically, as the insulator having a function of suppressing the permeation of impurities and oxygen, metal oxides such as alumina, magnesia, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, tantalum oxide, and metal nitrides such as aluminum nitride, silicon oxynitride, and silicon nitride can be used.

[0323] In addition, insulators that come into contact with a semiconductor, such as a gate insulator, or insulators disposed near a semiconductor layer are preferably insulators having regions containing excess oxygen. For example, when an insulator having a region containing excess oxygen comes into contact with a semiconductor layer, or when an insulator having a region containing excess oxygen is disposed near a semiconductor layer, oxygen vacancies in the semiconductor layer can be reduced. Examples of insulators that easily form regions containing excess oxygen include silicon oxide, silicon oxynitride, or porous silicon oxide.

[0324] In addition, examples of oxygen barrier insulators include oxides containing one or both of aluminum and hafnium, oxides containing hafnium and silicon (hafnium silicate), magnesium oxide, gallium oxide, gallium zinc oxide, indium gallium zinc oxide, silicon nitride, and silicon oxynitride. In addition, examples of oxides containing one or both of aluminum and hafnium include aluminum oxide, hafnium oxide, and oxides containing aluminum and hafnium (hafnium aluminate).

[0325] Examples of hydrogen barrier insulators include aluminum oxide, magnesium oxide, hafnium oxide, gallium oxide, indium gallium zinc oxide, silicon nitride, or silicon oxynitride.

[0326] Oxygen barrier insulators and hydrogen barrier insulators can be said to be insulators that block one or both of oxygen and hydrogen.

[0327] In addition, examples of insulators having the function of capturing or fixing hydrogen include oxides containing magnesium or oxides containing one or both of aluminum and hafnium. In addition, these oxides more preferably have an amorphous structure. Oxides having an amorphous structure sometimes have the property that oxygen atoms have dangling bonds and capture or fix hydrogen by these dangling bonds. In addition, these metal oxides preferably have an amorphous structure, but a part thereof may form a crystal region.

[0328] Note that in this specification and the like, a barrier insulator refers to an insulator having barrier properties. In addition, barrier properties refer to the property of not easily diffusing the corresponding substance (also referred to as the property of not easily allowing the corresponding substance to permeate, the property of low permeability of the corresponding substance, or the function of suppressing the diffusion of the corresponding substance). In addition, the function of capturing or fixing (also referred to as gettering) the corresponding substance can be interchanged with barrier properties. In addition, hydrogen as the corresponding substance refers to at least one of, for example, hydrogen atoms, hydrogen molecules, water molecules, and substances bonded to hydrogen bonds such as OH - and the like. In addition, unless otherwise specified, impurities as the corresponding substance refer to impurities in the channel formation region or the semiconductor layer, and for example, refer to hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N 2 O, NO, NO 2at least one of, for example, copper atoms. In addition, oxygen referred to as the corresponding substance means, for example, at least one of oxygen atoms, oxygen molecules, etc. Specifically, oxygen barrier property means the property of not easily diffusing at least one of oxygen atoms, oxygen molecules, etc.

[0329] [Conductive body]

[0330] As the conductive body, it is preferable to use a metal element selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, lanthanum, etc., an alloy composed of the above metal elements, or an alloy combining the above metal elements, etc. As the alloy composed of the above metal elements, a nitride or an oxide of the alloy can also be used. For example, it is preferable to use tantalum nitride, titanium nitride, tungsten, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel, etc. In addition, a highly conductive semiconductor represented by polysilicon containing impurity elements such as phosphorus and silicides such as nickel silicide can also be used.

[0331] In addition, a conductive material containing nitrogen such as a nitride containing tantalum, a nitride containing titanium, a nitride containing molybdenum, a nitride containing tungsten, a nitride containing ruthenium, a nitride containing tantalum and aluminum, or a nitride containing titanium and aluminum, a conductive material containing oxygen such as ruthenium oxide, an oxide containing strontium and ruthenium, or an oxide containing lanthanum and nickel, and a material containing metal elements such as titanium, tantalum, or ruthenium are conductive materials that are not easily oxidized, conductive materials having a function of suppressing oxygen diffusion, or materials that maintain conductivity even when absorbing oxygen, so they are preferable. As the conductive material containing oxygen, indium oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide, indium tin oxide containing titanium oxide, indium tin oxide added with silicon, indium zinc oxide, and indium zinc oxide containing tungsten oxide can be cited. In this specification, etc., a conductive film deposited using a conductive material containing oxygen is sometimes referred to as an oxide conductive film.

[0332] In addition, a conductive material mainly composed of tungsten, copper, or aluminum has high conductivity, so it is preferable.

[0333] In addition, multiple conductive layers formed of the above materials can also be laminated. For example, a laminated structure combining a material containing the above metal elements and a conductive material containing oxygen can also be adopted. In addition, a laminated structure combining a material containing the above metal elements and a conductive material containing nitrogen can also be adopted. In addition, a laminated structure combining a material containing the above metal elements, a conductive material containing oxygen, and a conductive material containing nitrogen can also be adopted.

[0334] In addition, in the case where a metal oxide is used for a channel formation region of a transistor, a conductor serving as a gate electrode preferably has a stacked structure combining a material containing the above metal element and a conductive material containing oxygen. In this case, it is preferable to dispose the conductive material containing oxygen on the channel formation region side. By disposing the conductive material containing oxygen on the channel formation region side, oxygen released from the conductive material is easily supplied to the channel formation region.

[0335] In particular, as the conductor serving as the gate electrode, a conductive material containing a metal element and oxygen contained in the metal oxide in which the channel is formed is preferably used. In addition, a conductive material containing the above metal element and nitrogen may also be used. For example, a nitrogen-containing conductive material such as titanium nitride or tantalum nitride may be used. In addition, indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, or indium tin oxide added with silicon, or one or more thereof may be used. In addition, indium gallium zinc oxide containing nitrogen may be used. By using the above materials, hydrogen contained in the metal oxide in which the channel is formed may sometimes be captured. Or, hydrogen mixed from an external insulator or the like may sometimes be captured.

[0336] [Metal Oxide]

[0337] Metal oxides sometimes have lattice defects. Lattice defects refer to point defects such as atomic vacancies and foreign atoms, line defects such as dislocations, plane defects such as grain boundaries, and volume defects such as voids. In addition, as causes for the generation of lattice defects, there are deviations in the ratio of the number of atoms of constituent elements (excess or deficiency of constituent atoms) and impurities.

[0338] When a metal oxide is used for a semiconductor layer of a transistor, lattice defects in the metal oxide cause generation or capture of carriers, etc. Therefore, when a metal oxide with many lattice defects is used for a semiconductor layer of a transistor, the electrical characteristics of the transistor may be unstable. Therefore, lattice defects in the metal oxide used for the semiconductor layer of a transistor are preferably few.

[0339] The types of lattice defects that are likely to exist in a metal oxide and the amount of lattice defects present differ depending on the structure of the metal oxide or the deposition method of the metal oxide, etc.

[0340] The structure of a metal oxide is classified into a single crystal structure and other structures (non-single crystal structures). As non-single crystal structures, for example, there are CAAC structures, polycrystalline structures, nc structures, amorphous-like (a-like) structures, and amorphous structures. The a-like structure has a structure intermediate between the nc structure and the amorphous structure. Note that the classification of crystal structures will be described later.

[0341] In addition, voids or low-density regions exist in metal oxides having an a-like structure and metal oxides having an amorphous structure. In other words, the crystallinity of metal oxides having an a-like structure and metal oxides having an amorphous structure is lower than that of metal oxides having an nc structure and metal oxides having a CAAC structure. In addition, the hydrogen concentration in the metal oxides of the metal oxides having an a-like structure is higher than that of the metal oxides having an nc structure and the metal oxides having a CAAC structure. Therefore, lattice defects are likely to be generated in metal oxides having an a-like structure and metal oxides having an amorphous structure.

[0342] Therefore, it is preferable to use a metal oxide having high crystallinity for the semiconductor layer of the transistor. For example, it is preferable to use a metal oxide having a CAAC structure or a single crystal structure. By using this metal oxide for the transistor, a transistor having good electrical characteristics can be realized. In addition, a transistor having high reliability can be realized.

[0343] In addition, it is preferable to use a metal oxide that increases the on-state current of the transistor for the channel formation region of the transistor. In order to increase the on-state current of the transistor, it is only necessary to increase the carrier mobility of the metal oxide used for the transistor. In order to increase the carrier mobility of the metal oxide, it is necessary to improve the transport of carriers (electrons in the case of an n-channel transistor) or reduce the scattering factors that affect the transport of carriers. In addition, carriers flow from the source electrode to the drain electrode through the channel formation region. Therefore, by providing a channel formation region in which carriers easily flow in the channel length direction, the on-state current of the transistor can be increased.

[0344] Here, it is preferable to use a metal oxide having high crystallinity for the metal oxide having a channel formation region. Furthermore, the crystal preferably has a crystal structure in which a plurality of layers (for example, a first layer, a second layer, and a third layer) are stacked. In other words, the crystal has a layered crystal structure (also referred to as a layered crystal or a layered structure). At this time, the c-axis direction of the crystal is the direction in which a plurality of layers are stacked. Metal oxides having such a crystal include, for example, single crystal oxide semiconductors, CAAC-OS, and the like.

[0345] In addition, the c-axis of the above crystal is preferably oriented in the normal direction of the formation surface or film surface of the metal oxide. As a result, a plurality of layers are arranged in parallel or substantially parallel to the formation surface or film surface of the metal oxide. That is, a plurality of layers extend in the channel length direction.

[0346] For example, the above-mentioned three-layered crystal structure has the following structure. The first layer has an atomic coordination structure of an oxygen octahedron with the metal contained in the first layer at the center. In addition, the second layer has an atomic coordination structure of an oxygen trigonal bipyramid or a tetrahedron with the metal contained in the second layer at the center. In addition, the third layer has an atomic coordination structure of an oxygen trigonal bipyramid or a tetrahedron with the metal contained in the third layer at the center.

[0347] As the crystal structure of the above crystal, for example, there is a YbFe 2 O 4 type structure, a Yb 2 Fe 3 O 7 type structure, their deformed structures, and the like.

[0348] Furthermore, it is preferable that the first to third layers are each composed of one metal element or a plurality of metal elements having the same valence and oxygen. Note that it is preferable that the valence of one or more metal elements constituting the first layer is the same as the valence of one or more metal elements constituting the second layer. In addition, the first layer and the second layer may also contain the same metal element. In addition, it is preferable that the valence of one or more metal elements constituting the first layer is different from the valence of one or more metal elements constituting the third layer.

[0349] By adopting the above structure, the crystallinity of the metal oxide can be improved, and the carrier mobility of the metal oxide can be increased. As a result, by using the metal oxide for the channel formation region of a transistor, the on-state current of the transistor increases, and the electrical characteristics of the transistor can be improved.

[0350] As the metal oxide of one aspect of the present invention, for example, indium oxide, gallium oxide, and zinc oxide can be cited. The metal oxide of one aspect of the present invention preferably contains at least indium (In) or zinc (Zn). In addition, the metal oxide preferably contains two or three selected from indium, element M, and zinc. Note that element M is a metal element or a metalloid element having a high bonding energy with oxygen, for example, a metal element or a metalloid element having a higher bonding energy with oxygen than indium. As element M, specifically, aluminum, gallium, tin, yttrium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zirconium, molybdenum, hafnium, tantalum, tungsten, lanthanum, cerium, neodymium, magnesium, calcium, strontium, barium, boron, silicon, germanium, and antimony, etc. can be cited. The element M contained in the metal oxide is preferably one or more of the above elements, more preferably one or more selected from aluminum, gallium, tin, and yttrium, and further preferably gallium. When the element M contained in the metal oxide is gallium, the metal oxide of one aspect of the present invention preferably contains one or more selected from indium, gallium, and zinc. Note that in this specification and the like, metal elements and metalloid elements are sometimes collectively referred to as "metal elements", and the "metal elements" described in this specification and the like sometimes include metalloid elements.

[0351] As a metal oxide semiconductor according to one aspect of the present invention, for example, indium zinc oxide (In-Zn oxide), indium tin oxide (In-Sn oxide), indium titanium oxide (In-Ti oxide), indium gallium oxide (In-Ga oxide), indium gallium aluminum oxide (In-Ga-Al oxide), indium gallium tin oxide (In-Ga-Sn oxide), gallium zinc oxide (Ga-Zn oxide, also denoted as GZO), aluminum zinc oxide (Al-Zn oxide, also denoted as AZO), indium aluminum zinc oxide (In-Al-Zn oxide, also denoted as IAZO), indium tin zinc oxide (In-Sn-Zn oxide), indium titanium zinc oxide (In-Ti-Zn oxide), indium gallium zinc oxide (In-Ga-Zn oxide, also denoted as IGZO), indium gallium tin zinc oxide (In-Ga-Sn-Zn oxide, also denoted as IGZTO), indium gallium aluminum zinc oxide (In-Ga-Al-Zn oxide, also denoted as IGAZO or IAGZO), etc. may be used. Alternatively, indium tin oxide containing silicon, gallium tin oxide (Ga-Sn oxide), aluminum tin oxide (Al-Sn oxide), etc. may be cited.

[0352] By increasing the atomic number ratio of indium to the total number of atomic numbers of all metal elements in the metal oxide, the field effect mobility of the transistor can be increased.

[0353] Note that the metal oxide may also contain one or more of the metal elements with a large period number in the periodic table instead of indium. Alternatively, the metal oxide may also contain one or more of the metal elements with a large period number in the periodic table in addition to indium. There is a tendency that the larger the orbital overlap of the metal element, the greater the carrier conduction in the metal oxide. Therefore, by containing the metal elements with a large period number in the periodic table, the field effect mobility of the transistor can sometimes be increased. As the metal elements with a large period number in the periodic table, metal elements belonging to the 5th period and metal elements belonging to the 6th period, etc. may be cited. Specifically, as the metal element, yttrium, zirconium, silver, cadmium, tin, antimony, barium, lead, bismuth, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, etc. may be cited. Note that lanthanum, cerium, praseodymium, neodymium, promethium, samarium, and europium are called light rare earth elements.

[0354] In addition, the metal oxide may also contain one or more non-metal elements. By the metal oxide containing non-metal elements, the field effect mobility of the transistor can sometimes be increased. As the non-metal element, for example, carbon, nitrogen, phosphorus, sulfur, selenium, fluorine, chlorine, bromine, hydrogen, etc. may be cited.

[0355] In addition, by increasing the atomic ratio of zinc with respect to the total number of atoms of all metal elements in the metal oxide, the metal oxide can have high crystallinity, thereby suppressing the diffusion of impurities in the metal oxide. Therefore, variations in the electrical characteristics of the transistor are suppressed, and reliability can be improved.

[0356] In addition, by increasing the atomic ratio of element M with respect to the total number of atoms of all metal elements in the metal oxide, the formation of oxygen vacancies in the metal oxide can be suppressed. Therefore, the generation of carriers due to oxygen vacancies is suppressed, and a transistor with a small off-state current can be realized. In addition, variations in the electrical characteristics of the transistor are suppressed, and reliability can be improved.

[0357] In addition, by increasing the ratio of the number of In atoms with respect to the total number of atoms of all metal elements in the metal oxide, a transistor with a large on-state current and high frequency characteristics can be obtained.

[0358] In the present embodiment, as the metal oxide, an In-Ga-Zn oxide may be described as an example.

[0359] In order to form a metal oxide having the above-described layered crystal structure, it is preferable to deposit atoms layer by layer. In the method for depositing a metal oxide according to one aspect of the present invention, since the ALD method is used, a metal oxide having the above-described layered crystal structure can be easily formed.

[0360] [[Transistor including metal oxide]]

[0361] Next, a case where a metal oxide (oxide semiconductor) is used for a transistor will be described. Hereinafter, a transistor using an oxide semiconductor in the semiconductor layer may be referred to as an OS transistor, and a transistor using silicon in the semiconductor layer may be referred to as an Si transistor.

[0362] By using a metal oxide (oxide semiconductor) according to one aspect of the present invention for a transistor, a transistor with a high field-effect mobility can be realized. In addition, a transistor with high reliability can be realized. In addition, a miniaturized or highly integrated transistor can be realized. For example, a transistor with a channel length of 2 nm or more and 30 nm or less can be manufactured.

[0363] It is preferable to use an oxide semiconductor with a low carrier concentration for the channel formation region of the transistor. For example, the carrier concentration in the channel formation region of the oxide semiconductor can be 1×10 18 cm -3 Hereinafter, it is preferably 1×10 17 cm -3 Hereinafter, it is more preferably 1×10 15 cm -3 Hereinafter, it is more preferably 1×1013 cm -3 Hereinafter, it is more preferably 1×10 11 cm -3 Hereinafter, it is further preferably less than 1×10 10 cm -3 , and is 1×10 -9 cm -3 or more. In the case of aiming to reduce the carrier concentration of the oxide semiconductor film, the impurity concentration in the oxide semiconductor film can be reduced to reduce the density of defect states. In this specification and the like, a state with a low impurity concentration and a low density of defect states is referred to as high-purity intrinsic or substantially high-purity intrinsic. In addition, an oxide semiconductor with a low carrier concentration is sometimes referred to as a high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor.

[0364] Since the density of defect states of a high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor film is low, the density of trap states is sometimes also low.

[0365] In addition, it takes a long time for the charge trapped in the trap states of the oxide semiconductor to disappear and sometimes acts like a fixed charge. Therefore, the electrical characteristics of a transistor in which a channel formation region is formed in an oxide semiconductor with a high density of trap states are sometimes unstable.

[0366] Therefore, in order to stabilize the electrical characteristics of the transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. In order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in the nearby film. Examples of the impurity include hydrogen, carbon, nitrogen, etc. Note that the impurity in the oxide semiconductor refers to an element other than the main components constituting the oxide semiconductor. For example, an element with a concentration lower than 0.1 atomic% can be said to be an impurity.

[0367] In addition, the band gap of the oxide semiconductor is preferably larger than the band gap of silicon (typically 1.1 eV), preferably 2 eV or more, more preferably 2.5 eV or more, and still more preferably 3.0 eV or more. By using an oxide semiconductor with a band gap larger than that of silicon, the off-state current (also referred to as Ioff) of the transistor can be reduced.

[0368] In addition, in Si transistors, the short-channel effect (also referred to as Short Channel Effect: SCE) appears as the transistors are miniaturized. Therefore, it is difficult to miniaturize Si transistors. One of the reasons for the appearance of the short-channel effect can be cited as the relatively small band gap of silicon. On the other hand, in OS transistors, an oxide semiconductor with a large band gap is used as the semiconductor material, so the short-channel effect can be suppressed. In other words, OS transistors are transistors without or with very little short-channel effect.

[0369] The short-channel effect refers to the degradation of electrical characteristics that occurs with the miniaturization of transistors (reduction in channel length). Specific examples of the short-channel effect include a decrease in the threshold voltage, an increase in the subthreshold swing value (sometimes denoted as the S value), and an increase in the leakage current. Here, the S value refers to the change in the gate voltage in the subthreshold region when the drain current value changes by one order of magnitude with a fixed drain voltage.

[0370] As an index of the tolerance to the short-channel effect, the characteristic length is widely used. The characteristic length is an index of the curvature of the potential in the channel formation region. The smaller the characteristic length, the steeper the potential rise, so it can be said that the ability to resist the short-channel effect is high.

[0371] The OS transistor is an accumulation-type transistor, and the Si transistor is an inversion-type transistor. Therefore, compared with the Si transistor, the characteristic length between the source region and the channel formation region and the characteristic length between the drain region and the channel formation region in the OS transistor are smaller. Therefore, the OS transistor has a higher ability to resist the short-channel effect than the Si transistor. That is to say, when a transistor with a small channel length is to be fabricated, the OS transistor is more suitable than the Si transistor.

[0372] When the carrier concentration of the oxide semiconductor is reduced until the channel formation region becomes i-type or substantially i-type, in a short-channel transistor, due to the Conduction-Band-Lowering (CBL) effect, the lower end of the conduction band in the channel formation region drops, and thus the energy difference between the lower end of the conduction band between the source region or the drain region and the channel formation region may be reduced to more than 0.1 eV and less than 0.2 eV. Thus, the OS transistor can be regarded as having an n + / n - / n + accumulation-type junctionless transistor structure or an n + / n - / n + accumulation-type non-junction transistor structure, where the channel formation region is an n - -type region, and the source region and the drain region are n + -type regions.

[0373] With the OS transistor having the above structure, good electrical characteristics can be achieved even when the storage device is miniaturized or highly integrated. For example, even when the channel length or gate length of the OS transistor is 20 nm or less, 15 nm or less, 10 nm or less, 7 nm or less, or 6 nm or less and 1 nm or more, 3 nm or more, or 5 nm or more, good electrical characteristics can be obtained. On the other hand, in Si transistors, the short-channel effect occurs, and thus it is sometimes difficult to set the gate length to 20 nm or less or 15 nm or less. Therefore, compared with Si transistors, OS transistors are more suitable for use as transistors with a small channel length. Note that the gate length refers to the length of the gate electrode in the direction in which carriers migrate in the channel formation region during transistor operation.

[0374] In addition, by miniaturizing the OS transistor, the high-frequency characteristics of the transistor can be improved. Specifically, the cut-off frequency of the transistor can be increased. When the gate length of the OS transistor is within the above range, for example, at room temperature, the cut-off frequency of the transistor can be 50 GHz or more, preferably 100 GHz or more, and more preferably 150 GHz or more.

[0375] As described above, the OS transistor has excellent effects compared with Si transistors, such as a small off-state current and the ability to fabricate transistors with a small channel length.

[0376] [[Impurities in metal oxides]]

[0377] Here, the effects of various impurities in the metal oxide (oxide semiconductor) are described.

[0378] When the oxide semiconductor contains silicon or carbon, which is one of the Group 14 elements, defect states are formed in the oxide semiconductor. Thus, the carbon concentration in the channel formation region of the oxide semiconductor measured by SIMS is set to 1×10 20 atoms / cm 3 or less, preferably 5×10 19 atoms / cm 3 or less, more preferably 3×10 19 atoms / cm 3 or less, more preferably 1×10 19 atoms / cm 3 or less, more preferably 3×10 18 atoms / cm 3 or less, further preferably 1×10 18 atoms / cm 3 or less. In addition, the silicon concentration in the channel formation region of the oxide semiconductor measured by SIMS is set to 1×10 20 atoms / cm 3Hereinafter, preferably 5×10 19 atoms / cm 3 Hereinafter, more preferably 3×10 19 atoms / cm 3 Hereinafter, more preferably 1×10 19 atoms / cm 3 Hereinafter, more preferably 3×10 18 atoms / cm 3 Hereinafter, further preferably 1×10 18 atoms / cm 3 Hereinafter.

[0379] When the oxide semiconductor contains nitrogen, electrons are generated as carriers, increasing the carrier concentration and making it easy to be n-type. As a result, a transistor using an oxide semiconductor containing nitrogen is likely to have a normally-on characteristic. Or, when the oxide semiconductor contains nitrogen, trap states may be formed. As a result, the electrical characteristics of the transistor may sometimes be unstable. Therefore, the nitrogen concentration in the channel formation region of the oxide semiconductor measured by SIMS is set to 1×10 20 atoms / cm 3 Hereinafter, preferably 5×10 19 atoms / cm 3 Hereinafter, more preferably 1×10 19 atoms / cm 3 Hereinafter, more preferably 5×10 18 atoms / cm 3 Hereinafter, more preferably 1×10 18 atoms / cm 3 Hereinafter, further preferably 5×10 17 atoms / cm 3 Hereinafter.

[0380] The hydrogen contained in the oxide semiconductor reacts with the oxygen bonded to the metal atoms to generate water, so oxygen vacancies may sometimes be formed. When hydrogen enters the oxygen vacancies, electrons may sometimes be generated as carriers. In addition, sometimes due to a part of the hydrogen bonding with the oxygen bonded to the metal atoms, electrons are generated as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen is likely to have a normally-on characteristic. Thus, it is preferable to minimize the hydrogen in the channel formation region of the oxide semiconductor as much as possible. Specifically, the hydrogen concentration in the channel formation region of the oxide semiconductor measured by SIMS is set to be less than 1×10 20 atoms / cm 3 , preferably less than 5×10 19 atoms / cm 3 , more preferably less than 1×10 19atoms / cm 3 , more preferably less than 5×10 18 atoms / cm 3 , still more preferably less than 1×10 18 atoms / cm 3 .

[0381] In addition, when the oxide semiconductor contains an alkali metal or an alkaline earth metal, defect states are sometimes formed to generate carriers. Therefore, a transistor using an oxide semiconductor containing an alkali metal or an alkaline earth metal tends to have a normally-on characteristic. Thus, the concentration of the alkali metal or alkaline earth metal in the channel formation region of the oxide semiconductor measured by SIMS is set to 1×10 18 atoms / cm 3 or less, preferably 2×10 16 atoms / cm 3 or less.

[0382] By using an oxide semiconductor with sufficiently reduced impurities for the channel formation region of the transistor, the transistor can have stable electrical characteristics.

[0383] [Other semiconductor materials]

[0384] The oxide semiconductor 230 can be equivalently referred to as a semiconductor layer having a channel formation region of a transistor. The semiconductor material that can be used for the semiconductor layer is not limited to the above metal oxides. As the semiconductor layer, a semiconductor material having a bandgap (a semiconductor material that is not a zero-bandgap semiconductor) can also be used. For example, a single-element semiconductor, a compound semiconductor, or a layered material (also referred to as an atomic layer material, a two-dimensional material, etc.) is preferably used as the semiconductor material.

[0385] Here, in this specification, etc., the layered material is a general term for a group of materials having a layered crystal structure. The layered crystal structure is a structure in which layers formed by covalent bonds or ionic bonds are stacked by a bond weaker than covalent bonds and ionic bonds such as van der Waals forces. The layered material has high conductivity in the unit layer, that is, has high two-dimensional conductivity. By using a material that is used as a semiconductor and has high two-dimensional conductivity for the channel formation region, a transistor with a large on-state current can be provided.

[0386] Examples of the single-element semiconductor that can be used for the semiconductor material include silicon and germanium. Examples of the silicon that can be used for the semiconductor layer include single-crystalline silicon, polycrystalline silicon, microcrystalline silicon, and amorphous silicon. As the polycrystalline silicon, for example, low-temperature polycrystalline silicon (LTPS: Low Temperature Poly Silicon) can be cited.

[0387] As compound semiconductors that can be used for semiconductor materials, silicon carbide, silicon germanium, gallium arsenide, indium phosphide, boron nitride, boron arsenide, etc. can be cited. Boron nitride that can be used for the semiconductor layer preferably has an amorphous structure. Boron arsenide that can be used for the semiconductor layer preferably contains crystals having a cubic crystal structure.

[0388] As layered materials, there are graphene, silicene, boron carbonitride, chalcogenides, etc. In boron carbonitride as a layered material, carbon atoms, nitrogen atoms, and boron atoms are arranged in a hexagonal lattice structure on a plane. Chalcogenides are compounds containing chalcogen elements. In addition, chalcogen elements are a general term for elements belonging to Group 16, including oxygen, sulfur, selenium, tellurium, polonium, and livermorium. In addition, as chalcogenides, transition metal chalcogenides, Group 13 chalcogenides, etc. can be cited.

[0389] As the semiconductor layer, for example, it is preferable to use transition metal chalcogenides used as semiconductors. As transition metal chalcogenides that can be used as the semiconductor layer, specifically, molybdenum sulfide (typically MoS 2 ), molybdenum selenide (typically MoSe 2 ), molybdenum telluride (typically MoTe 2 ), tungsten sulfide (typically WS 2 ), tungsten selenide (typically WSe 2 ), tungsten telluride (typically WTe 2 ), hafnium sulfide (typically HfS 2 ), hafnium selenide (typically HfSe 2 ), zirconium sulfide (typically ZrS 2 ), zirconium selenide (typically ZrSe 2 ), etc. can be cited. By using the above transition metal chalcogenides for the semiconductor layer, a storage device with a large on-state current can be provided.

[0390] <Variant Example 1>

[0391] Hereinafter, Figures 10A to 13D is used to illustrate an example of a semiconductor device according to one aspect of the present invention.

[0392] In Figures 10A to 13D , the difference between the semiconductor devices shown in each of FIGS. A to D and the semiconductor device shown in Figures 1A to 1D lies in the shape of the insulator 223. Hereinafter, mainly the parts different from the description of the above <Structural Example 1> will be described, and the description of the repeated parts will be omitted with reference to the above description.

[0393] In addition, in the semiconductor devices shown in FIGS. A to D, the same reference numerals are assigned to the elements having the same functions as the elements constituting the semiconductor device shown in <Structural Example 1>. Note that the materials constituting the semiconductor device in this section may be the materials described in detail in <Structural Example 1>.

[0394] [Modification Example 1-1]

[0395] Figures 10A to 10D Shows Figures 1A to 1D A modification example of the semiconductor device shown. Figures 10A to 10D Is a plan view and a cross-sectional view of the semiconductor device.

[0396] In Figures 10A to 10D In the semiconductor device shown, the insulator 223 is processed into a strip shape. For example, as Figure 10A And Figure 10B Shown, the insulator 223 is disposed to extend in the channel length direction (A1 - A2 direction).

[0397] In addition, as Figure 10A And Figure 10D Shown, the side end portion on the A5 side of the insulator 223 coincides with the side end portion on the A5 side of the oxide semiconductor 230. In addition, the side end portion on the A6 side of the insulator 223 coincides with the side end portion on the A6 side of the oxide semiconductor 230.

[0398] In the above structure, as Figure 10B And Figure 10D Shown, the insulator 275 is disposed in contact with the top surface of the insulator 222, the top surface and side surfaces of the insulator 223, the side surfaces of the oxide semiconductor 230, the side surfaces and top surface of the conductor 242a, and the side surfaces and top surface of the conductor 242b. In this structure, both the region 231a and the region 231b are also surrounded by the insulator 223 and the insulator 275.

[0399] The insulator 223 is preferably formed before depositing the oxide semiconductor film that becomes the oxide semiconductor 230.

[0400] Note that Figure 10A And Figure 10D Show a structure in which the side end portion of the insulator 223 coincides with the side end portion of the oxide semiconductor 230 in a cross-section in the channel width direction, but the present invention is not limited thereto. For example, in a cross-section in the channel width direction, the side end portion of the insulator 223 may also be located outside the side end portion of the oxide semiconductor 230.

[0401] [Modification Example 1-2]

[0402] Figures 11A to 11D Shows Figures 1A to 1DModified examples of the semiconductor device shown. Figures 11A to 11D are a plan view and a cross-sectional view of the semiconductor device.

[0403] In Figures 11A to 11D the semiconductor device shown, the insulator 223 is processed into a strip shape. For example, as Figure 11A and Figure 11D shown, the insulator 223 is disposed to extend in the channel width direction (A3 - A4 direction). Further, the insulator 223 is disposed to extend in the direction in which the conductor 260 extends.

[0404] In addition, as Figure 11A and Figure 11B shown, the side end portion on the A1 side of the insulator 223 coincides with the side end portion on the A1 side of the oxide semiconductor 230. Further, the side end portion on the A2 side of the insulator 223 coincides with the side end portion on the A2 side of the oxide semiconductor 230.

[0405] In the above structure, as Figure 11B and Figure 11D shown, the insulator 275 is disposed so as to contact the top surface of the insulator 222, the top surface and side surfaces of the insulator 223, the side surfaces of the oxide semiconductor 230, the side surfaces and top surface of the conductor 242a, and the side surfaces and top surface of the conductor 242b. In this structure, both the region 231a and the region 231b are also surrounded by the insulator 223 and the insulator 275.

[0406] The insulator 223 is preferably formed before depositing the oxide semiconductor film that becomes the oxide semiconductor 230.

[0407] Note that Figure 11A and Figure 11B show a structure in which the side end portion of the insulator 223 coincides with the side end portion of the oxide semiconductor 230 in a cross-section in the channel length direction, but the present invention is not limited thereto. For example, in a cross-section in the channel length direction, the side end portion of the insulator 223 may also be located outside the side end portion of the oxide semiconductor 230.

[0408] [Modified Examples 1 - 3]

[0409] Figures 12A to 12D Shows Figures 1A to 1E modified examples of the semiconductor device shown. Figures 12A to 12D are a plan view and a cross-sectional view of the semiconductor device.

[0410] In Figures 12A to 12D the semiconductor device shown, the insulator 223 is processed into an island shape. In addition, as Figures 12A to 12D shown, the side end portion of the insulator 223 coincides with the side end portion of the oxide semiconductor 230.

[0411] Note that, in this specification and the like, "island-shaped" or "band-shaped" means a state in which two or more layers formed in the same process and using the same material are physically separated.

[0412] In the above structure, as Figures 12B to 12D shown, the insulator 275 is disposed in contact with the top surface of the insulator 222, the side surface of the insulator 223, the side surfaces of the oxide semiconductor 230, the side surface and the top surface of the conductor 242a, and the side surface and the top surface of the conductor 242b. In this structure, both the region 231a and the region 231b are also surrounded by the insulator 223 and the insulator 275.

[0413] The insulator 223 is preferably formed by processing the oxide semiconductor film and the insulating film into an island shape after depositing the insulating film that becomes the insulator 223 and the oxide semiconductor film that becomes the oxide semiconductor 230. By forming the insulator 223 in this way, the side end portions of the insulator 223 can be made to coincide with the side end portions of the oxide semiconductor 230.

[0414] Note that, not limited to the above method, the insulator 223 may also be formed before depositing the oxide semiconductor film that becomes the oxide semiconductor 230.

[0415] Note that, Figure 12A and Figure 12B show a structure in which the side end portions of the insulator 223 coincide with the side end portions of the oxide semiconductor 230, but the present invention is not limited thereto. For example, in a cross section in the channel length direction, the side end portions of the insulator 223 may also be located outside the side end portions of the oxide semiconductor 230. Further, in a cross section in the channel width direction, the side end portions of the insulator 223 may also be located outside the side end portions of the oxide semiconductor 230.

[0416] Figures 12A to 12D shows a structure in which the insulator 222 is in contact with the insulator 223, but the present invention is not limited thereto. For example, an insulator may also be provided between the insulator 222 and the insulator 223.

[0417] For example, as Figures 13A to 13D shown, an island-shaped insulator 221 may also be provided between the insulator 222 and the insulator 223. Further, the side end portions of the insulator 221 coincide with the side end portions of the insulator 223.

[0418] The thickness of the insulator 221 is preferably larger than the thickness of the insulator 250. In addition, the sum of the thickness of the insulator 221 and the thickness of the insulator 223 is preferably larger than the thickness of the insulator 250. By adopting such a structure, in the cross-section in the channel width direction of the transistor 200, the bottom surface of the conductor 260 in the region not overlapping with the oxide semiconductor 230 is lower than the bottom surface of the oxide semiconductor 230. In addition, the bottom surface of the conductor 260 in the region not overlapping with the oxide semiconductor 230 is located closer to the insulator 222 side than the bottom surface of the oxide semiconductor 230. Thus, a structure is formed in which the conductor 260 serving as a gate electrode covers the side surface and the top surface of the channel formation region of the oxide semiconductor 230 with the insulator 250 interposed therebetween, and it is easy for the electric field of the conductor 260 to act on the entire channel formation region of the oxide semiconductor 230. Thereby, the on-state current and the frequency characteristics of the transistor 200 can be improved.

[0419] In the above structure, as Figure 13B and Figure 13D shown, the insulator 275 is provided in contact with the top surface of the insulator 222, the side surface of the insulator 221, the side surface of the insulator 223, the side surface of the oxide semiconductor 230, the side surface and the top surface of the conductor 242a, and the side surface and the top surface of the conductor 242b. In this structure, both the region 231a and the region 231b are also surrounded by the insulator 223 and the insulator 275.

[0420] The insulator 221 is preferably formed by processing these films into an island shape after depositing the insulating film that becomes the insulator 221, the insulating film that becomes the insulator 223, and the oxide semiconductor film that becomes the oxide semiconductor 230. Alternatively, the insulator 221 is preferably formed by processing these films into an island shape after depositing the insulating film that becomes the insulator 221 and the insulating film that becomes the insulator 223. By forming the insulator 221 using the above method, the side end portion of the insulator 221 can be made to coincide with the side end portion of the insulator 223.

[0421] Note that, not limited to the above method, the insulator 221 may also be formed before depositing the insulating film that becomes the insulator 223.

[0422] Note that, Figure 13A and Figure 13B show a structure in which the side end portion of the insulator 221 coincides with the side end portion of the insulator 223, but the present invention is not limited thereto. For example, in the cross-section in the channel length direction, the side end portion of the insulator 221 may also be located outside the side end portion of the insulator 223. In addition, in the cross-section in the channel width direction, the side end portion of the insulator 221 may also be located outside the side end portion of the insulator 223.

[0423] In Figures 10A to 13DIn the semiconductor device shown in A to D of each figure, the insulator 222 and the structure on the insulator 223 are Figures 1A to 1D The insulator 222 and the structure on the insulator 223 of the semiconductor device shown in FIG. 1 are the same, but the present invention is not limited to this. The insulator 222 and the structure on the insulator 223 of the semiconductor device shown in FIG. 1 may also be the same as the structure on the insulator 222 and the structure on the insulator 223 of the semiconductor device shown in FIG. Figures 4A to 9D The structures on the insulator 222 and the insulator 223 of any of the semiconductor devices shown in the drawings are the same.

[0424] In addition, Figures 5A to 5D Similarly to the semiconductor device shown in FIGS. A to D , the semiconductor device shown in FIGS. 2A to 2B may include a conductor 215 and an insulator 216 below the insulator 222 .

[0425] <Structure Example 2>

[0426] In this section, reference is made to Figures 14A to 32D A semiconductor device having a structure different from that of the semiconductor device described in the above-mentioned <Structural Example 1> will be described.

[0427] exist Figures 14A to 32D In the semiconductor device shown, components having the same functions as those of the components constituting the semiconductor device shown in <Structural Example 1> are denoted by the same reference numerals. Note that the materials constituting the semiconductor device in this section can use the materials described in detail in <Structural Example 1>.

[0428] In the above-mentioned <Structural Example 1>, the channel formation region, the source region, and the drain region of the oxide semiconductor 230 are provided on the insulator 223. That is, the channel formation region, the source region, and the drain region of the oxide semiconductor 230 are provided on the same insulator. In other words, the insulator provided below the channel formation region, the insulator provided below the source region, and the insulator provided below the drain region are formed using the same insulating material.

[0429] As described in the above <Structural Example 1>, a transistor using an oxide semiconductor as a semiconductor layer preferably adopts a structure in which oxygen is supplied to the channel formation region and excessive oxygen is not supplied to the source region and the drain region. As long as such a structure can be adopted, the insulator disposed below the channel formation region may be different from the insulator disposed below the source region and the insulator disposed below the drain region. In other words, the insulator disposed below the channel formation region, the insulator disposed below the source region, and the insulator disposed below the drain region may also be formed using different insulating materials.

[0430] [Structural Example 2-1]

[0431] Reference Figures 14A to 14D Another example of the structure of a semiconductor device will be described.Figures 14A to 14D is a plan view and a cross-sectional view of a semiconductor device including a transistor 200A.

[0432] Figures 14A to 14D The semiconductor device shown Figures 1A to 1D The main difference from the semiconductor device shown is the structure of the insulator 223. The following mainly describes the parts different from the description of the above <Structure Example 1>, and the description of the repeated parts is sometimes omitted with reference to the above description.

[0433] As Figures 14A to 14D shown, the insulator 223 includes an insulator 223a, an insulator 223b, and an insulator 223c located between the insulator 223a and the insulator 223b. That is, the transistor 200A includes an insulator 223a, an insulator 223b, and an insulator 223c located between the insulator 223a and the insulator 223b on the insulator 222. In addition, the transistor 200A includes an oxide semiconductor 230 on the insulator 223a, the insulator 223b, and the insulator 223c. The insulators 223a to 223c are all arranged to extend in the channel width direction (A3 - A4 direction) of the transistor 200A. In addition, the insulator 223a has an area overlapping with the conductor 242a, the insulator 223b has an area overlapping with the conductor 242b, and the insulator 223c has an area overlapping with the insulator 250 and the conductor 260. In addition, the heights of the top surfaces of each of the insulators 223a to 223c are the same as each other. In other words, the thicknesses of each of the insulators 223a to 223c are the same as each other.

[0434] Figure 14E shows a perspective schematic view of the above semiconductor device. In Figure 14E , a part of the insulator 222, the insulator 223, the oxide semiconductor 230, the conductor 242b, the insulator 250, the conductor 260, the insulator 275, and its periphery is cut off and shown. In addition, in Figure 14E , some constituent elements (for example, the insulator 280 and the insulator 283) are shown only by their outlines in dotted lines.

[0435] Here, Figure 15 shows Figure 14B an enlarged view of the channel formation region and its vicinity in Figure 15 The arrow shown is to visualize the case where oxygen in the insulator 280 diffuses through the insulator 250 to the region 231c.

[0436] As Figure 15As shown, the oxide semiconductor 230 has a region 231a overlapping with the conductor 242a, a region 231b overlapping with the conductor 242b, and a region 231c located between the region 231a and the region 231b. In addition, the region 231a has a region overlapping with the insulator 223a, the region 231b has a region overlapping with the insulator 223b, and the region 231c has a region overlapping with the insulator 223c.

[0437] In Figures 14A to 14D In the structure shown, the region 231a is surrounded by the insulator 223a and the insulator 275, and the region 231b is surrounded by the insulator 223b and the insulator 275. In addition, the region 231a is in contact with the insulator 223a and the insulator 275, and the region 231b is in contact with the insulator 223b and the insulator 275.

[0438] In addition, as Figure 14C shown, the insulator 250 has a structure in contact with a part of the top surface of the insulator 223c. At this time, the region 231c is surrounded by the insulator 223c and the insulator 250. In addition, the region 231c is in contact with the insulator 223c and the insulator 250.

[0439] As the insulator 223a, the insulator 223b, and the insulator 275, it is preferable to use the oxygen barrier insulator described in the above [insulator]. As the insulator 223a, the insulator 223b, and the insulator 275, for example, silicon nitride is preferably used. At this time, the insulator 223a, the insulator 223b, and the insulator 275 all contain silicon and nitrogen. By adopting such a structure, since the amount of oxygen supplied to the region 231a and the region 231b is less than that to the region 231c, a decrease in the carrier concentration in the source region and the drain region can be prevented.

[0440] Furthermore, the insulator 223a and the insulator 223b preferably have a compressive stress, and this compressive stress is preferably greater than that of the oxide semiconductor 230. For example, the compressive stress of the silicon nitride that can be used for the insulator 223a and the insulator 223b is greater than that of the oxide semiconductor 230. By using an insulator having a compressive stress as the insulator 223a and the insulator 223b, especially an insulator whose compressive stress is greater than that of the oxide semiconductor 230, a strain extending in the tensile direction (hereinafter sometimes referred to as tensile strain) can be formed in the region 231a and the region 231b. By stably forming V O H by the tensile strain, the region 231a and the region 231b can be made into stable n-type regions. Note that the compressive stress of the insulator is a stress that relaxes the compressive shape of the insulator and is a stress having a vector in the direction from the central part to the end part of the insulator.

[0441] In addition, as the insulators 223a, 223b, and 275, silicon nitride formed by ALD method is more preferably used, and silicon nitride formed by PEALD method is particularly preferably used. Since the ALD method has good step coverage and thickness uniformity, it is suitable for depositing thin films, covering surfaces with high aspect ratios, etc.

[0442] The insulators 223a and 223b preferably have at least oxygen barrier properties, so the thickness of the insulators 223a and 223b is preferably 1.0 nm or more, more preferably 1.4 nm or more. Note that there is no particular limitation on the upper limit value of the thickness of the insulators 223a and 223b. However, from the viewpoints of miniaturization or high integration of semiconductor devices and improvement of the productivity of semiconductor devices, the upper limit value is preferably 20 nm or less, 10 nm or less, or 5.0 nm or less. Therefore, the insulators 223a and 223b preferably include regions with a thickness of 1.0 nm or more and 10 nm or less, and more preferably include regions with a thickness of 1.0 nm or more and 5.0 nm or less. In addition, the insulators 223a and 223b preferably include regions with a thickness of 1.4 nm or more and 10 nm or less, and more preferably include regions with a thickness of 1.4 nm or more and 5.0 nm or less.

[0443] The insulators that can be used as the insulators 223a, 223b, and 275 are not limited to silicon nitride. For example, alumina can also be used. In addition, the insulators 223a, 223b, and 275 can also have a stacked structure.

[0444] A material different from that of the insulators 223a and 223b can also be used for the insulator 223c. In other words, the oxygen barrier property of the insulator 223c can be equal to, higher than, or lower than that of the insulators 223a and 223b. For example, since it is preferable to supply oxygen to the region 231c in contact with the insulator 223c, the oxygen barrier property of the insulator 223c is preferably lower than that of the insulators 223a and 223b. The insulator 223c only needs to have oxygen barrier properties, and is not limited to insulating materials as the insulator 223c, and semiconductor materials can also be used.

[0445] For example, silicon oxynitride or oxynitride silicon is preferably used as the insulator 223c. In addition, for example, metal oxides such as hafnium oxide, gallium oxide, gallium zinc oxide, or indium gallium zinc oxide are preferably used as the insulator 223c. By adopting this structure, oxygen can be efficiently supplied to the region 231c, so that the channel formation region can be made into an i-type region.

[0446] In addition, for example, by using an insulator such as silicon oxynitride or silicon nitride oxynitride, which has a higher oxygen content than nitrogen content compared to silicon nitride, as the insulator 223c, the amount of nitrogen diffused into the channel formation region can be reduced. Further, by using the above metal oxide as the insulator 223c, nitrogen mixing into the channel formation region can be suppressed.

[0447] The insulators 223a to 223c are preferably formed before depositing the oxide semiconductor film that becomes the oxide semiconductor 230.

[0448] For example, when the etching selectivity of the insulator 275 with respect to the insulator 223c is high, the insulator 223c is used as an etch stop film when etching the insulator 275 to form an opening. At this time, the insulator 223c in the region that overlaps with the opening formed in the insulator 275 and does not overlap with the oxide semiconductor 230 remains (see Figure 14C ). Therefore, the insulator 223c is provided as a continuous insulator extending in the channel width direction (A3 - A4 direction).

[0449] In addition, for example, when the etching selectivity of the insulator 275 with respect to the insulator 223c is low, when etching the insulator 275 to form an opening, the insulator 223c in the region that overlaps with the oxide semiconductor 230 remains, and the insulator 223c in the region that does not overlap with the oxide semiconductor 230 is removed. That is, an opening is formed in the insulator 223c. At this time, in the opening formed in the insulator 223c, the insulator 250 contacts a part of the top surface of the insulator 222 (see Figures 16A to 16D ).

[0450] In addition, for example, when the etching selectivity of the oxide semiconductor 230 with respect to the insulator 223c is low, when processing the oxide semiconductor film that becomes the oxide semiconductor 230 to form the island - shaped oxide semiconductor 230, the insulator 223c in the region that overlaps with the oxide semiconductor 230 remains, and the insulator 223c in the region that does not overlap with the oxide semiconductor 230 is removed. Therefore, the insulator 223c is formed in an island shape. At this time, the insulator 275 contacts a part of the top surface of the insulator 222 in the region that does not overlap with the insulators 223a and 223b (see Figures 17A to 17D ).

[0451] In Figures 14A to 14D the structure shown, Figures 16A to 16D the structure shown, and Figures 17A to 17D in each of the structures shown, the region 231a is surrounded by the insulators 223a and 275, and the region 231b is surrounded by the insulators 223b and 275.

[0452] In Figures 14A to 14DIn the semiconductor device shown, the insulator 223c may also use an insulating material containing the same elements as the insulator 222. In this case, it may not be possible to clearly detect the boundary between the insulator 222 and the insulator 223c.

[0453] When using an insulating material containing the same elements as the insulator 222 as the insulator 223c, the insulator 222 and the insulator 223c may also be formed by different processes respectively. Alternatively, the insulator 222 having a convex shape may be formed by processing the insulating film that becomes the insulator 222 (see Figures 18A to 18D ). The convex shape is preferably formed such that at least a part of it overlaps with the conductor 260. At this time, the region of the convex shape corresponds to Figures 14A to 14D the insulator 223c shown.

[0454] In addition, in Figures 14A to 14D the semiconductor device shown, the insulator 223c may also use a material containing the same elements as the oxide semiconductor 230. In this case, it may not be possible to clearly detect the boundary between the insulator 223c and the oxide semiconductor 230.

[0455] When using a material containing the same elements as the oxide semiconductor 230 as the insulator 223c, the insulator 223c and the oxide semiconductor 230 may also be formed by different processes respectively. Alternatively, after forming the insulators 223a and 223b, an oxide semiconductor film that becomes the oxide semiconductor 230 may be deposited, and the oxide semiconductor film may be processed to form the oxide semiconductor 230 having a region protruding downward (see Figures 19A to 19D ). The region protruding downward is preferably formed such that at least a part of it overlaps with the conductor 260. At this time, the region protruding downward corresponds to Figures 14A to 14D the insulator 223c shown.

[0456] In addition, when depositing an oxide semiconductor film that becomes the oxide semiconductor 230 on the insulators 223a and 223b, sometimes the height of the top surface of the region in the oxide semiconductor film that does not overlap with the insulators 223a and 223b is lower than the height of the top surface of the region that overlaps with the insulator 223a or the insulator 223b. Therefore, in the oxide semiconductor 230, the height of the top surface of the region that overlaps with the conductor 260 is sometimes lower than the height of the top surface of the region that overlaps with the conductor 242a or the conductor 242b.

[0457] Note that in Figures 14A to 14D , the insulators 223a to 223c are all provided to extend in the channel width direction of the transistor 200A, but the present invention is not limited to this. The insulator 223c may also be island-shaped.

[0458] For example, in Figures 20A to 20D the semiconductor device shown, the insulator 223 includes an island-shaped insulator 223c and an insulator 223a provided on the outer periphery of the insulator 223c when viewed in plan. At least a part of the insulator 223c has a region overlapping with the conductor 260 with the oxide semiconductor 230 therebetween. In such a structure, the region 231a is surrounded by the insulator 223a and the insulator 275, and the region 231b is surrounded by the insulator 223b and the insulator 275.

[0459] Note that in Figure 20C , the side end portion of the insulator 223c is located outside the side end portion of the oxide semiconductor 230, but the present invention is not limited thereto. For example, in the channel width direction of the transistor 200A, the side end portion of the insulator 223c may also coincide with the side end portion of the oxide semiconductor 230.

[0460] Note that in Figures 20A to 20D the semiconductor device shown, similar to the structure shown in Figures 18A to 18D , an insulator 222 having a convex shape (see Figures 21A to 21D ) may also be provided. At this time, the convex-shaped region corresponds to the insulator 223c.

[0461] In addition, in Figures 20A to 20D the semiconductor device shown, similar to the structure shown in Figures 19A to 19D , an oxide semiconductor 230 having a region protruding downward (see Figures 22A to 22D ) may also be provided. At this time, the region protruding downward corresponds to the insulator 223c.

[0462] In Figures 14B to 14D , a structure in which the oxide semiconductor 230 is a single layer is shown, but the present invention is not limited thereto. The oxide semiconductor layer 230 may also have a stacked structure. For example, as shown in Figures 23A to 23D , the oxide semiconductor 230 may also have a stacked structure of an oxide semiconductor 230a, an oxide semiconductor 230b on the oxide semiconductor 230a, and an oxide semiconductor 230c on the oxide semiconductor 230b.

[0463] In addition, in Figure 14B and Figure 14C , a single-layer insulator 250 is shown, but the present invention is not limited thereto. The insulator 250 may also have a stacked structure. For example, as shown in Figures 23A to 23D , the insulator 250 may also have a stacked structure of an insulator 250a, an insulator 250b on the insulator 250a, and an insulator 250c on the insulator 250b.

[0464] In addition, in Figure 14B and Figure 14CA single-layer conductor 260 is shown, but the present invention is not limited thereto. The conductor 260 may also have a laminated structure. For example, as Figures 23A to 23D shown, the conductor 260 may also have a laminated structure of a conductor 260a and a conductor 260b on the conductor 260a.

[0465] In addition, in Figure 14B and Figure 14D the conductors 242a and 242b both have a single layer, but the present invention is not limited thereto. The conductors 242a and 242b may also adopt a laminated structure. For example, as Figures 23A to 23D shown, the conductor 242a may also have a laminated structure of a conductor 242a1 and a conductor 242a2 on the conductor 242a1, and the conductor 242b may also have a laminated structure of a conductor 242b1 and a conductor 242b2 on the conductor 242b1.

[0466] Note that in Figure 14B and Figure 14D an insulator 275 is provided in contact with the top surfaces of the conductor 242a and the conductor 242b, but the present invention is not limited thereto. For example, as Figures 23A to 23D shown, an insulator 271a may also be provided between the conductor 242a and the insulator 275, and an insulator 271b may be provided between the conductor 242b and the insulator 275.

[0467] In addition, in Figures 14B to 14D the insulator 283 is provided in contact with the top surfaces of the insulator 280, the insulator 250, and the conductor 260, but the present invention is not limited thereto. For example, as Figures 23B to 23D shown, an insulator 282 may also be provided between the insulator 283 and the insulator 280, the insulator 250, and the conductor 260.

[0468] [Structural Example 2-2]

[0469] Although Figures 14A to 14D shows that the transistor 200A has a single-gate structure including one gate, the present invention is not limited to this structure. For example, the transistor 200A may also include a back gate.

[0470] Refer to Figures 24A to 24D to illustrate another example of the structure of the semiconductor device. Figures 24A to 24D are a plan view and a cross-sectional view of the semiconductor device. Figures 24A to 24D The semiconductor device shown includes a conductor 215 and an insulator 216, and is mainly different from the semiconductor device shown in Figures 14A to 14D in this regard. Hereinafter, the description of the parts repeated from the above [Structural Example 2-1] will be omitted with reference to the above description.

[0471] Figures 24A to 24D The structure, material, etc. of the conductor 215 shown are the same as those of Figures 5A to 5D the conductor 215 shown. Figures 24A to 24D The structure, material, etc. of the insulator 216 shown are the same as those of Figures 5A to 5D the insulator 216 shown. Therefore, the structure, material, etc. of the conductor 215 and the insulator 216 can be referred to the description of the above [Structure Example 1-2].

[0472] [Structure Example 2-3]

[0473] In Figures 24A to 24D , the side end of the conductor 242a coincides with the side end of the oxide semiconductor 230, and the side end of the conductor 242b coincides with the side end of the oxide semiconductor 230. However, the present invention is not limited to this structure. For example, the conductor 242a and the conductor 242b may also have regions in contact with the side surface of the oxide semiconductor 230.

[0474] Refer to Figures 25A to 25D to illustrate another example of the structure of the semiconductor device. Figures 25A to 25D is a plan view and a cross-sectional view of a semiconductor device including a transistor 200A.

[0475] Figures 25A to 25D The main difference between the transistor 200A shown and Figures 24A to 24D the transistor 200A shown lies in the shapes of the conductor 242a and the conductor 242b. Hereinafter, the parts that are repeated with the descriptions of the above [Structure Example 2-1] and [Structure Example 2-2] will be omitted with reference to the above descriptions.

[0476] Figures 25A to 25D The structure, material, etc. of the conductor 242a and the conductor 242b shown are the same as those of Figures 6A to 6D the conductor 242a and the conductor 242b shown. Therefore, the structure, material, etc. of the conductor 242a and the conductor 242b can be referred to the description of the above [Structure Example 1-3].

[0477] [Structure Example 2-4]

[0478] In Figures 24A to 24D , in the opening 290, the insulator 250 contacts the side surfaces of the insulator 280, the insulator 275, and the insulator 223. However, the present invention is not limited to this structure. For example, in the opening 290, an insulator may also be provided between the insulator 250 and the insulator 280, the insulator 275, and the insulator 223.

[0479] Refer to Figures 26A to 26DAnother example of the structure of a semiconductor device is described. Figures 26A to 26D It is a plan view and a cross-sectional view of a semiconductor device including a transistor 200A.

[0480] Figures 26A to 26D The transistor 200A shown includes an insulator 255 and is mainly different in this regard from Figures 24A to 24D the transistor 200A shown. In addition, Figures 26A to 26D a structure in which both the conductor 242a and the conductor 242b have a two-layer stacked structure is shown. Hereinafter, parts that are repetitive of the above descriptions of [Structure Example 2-1] and [Structure Example 2-2] are omitted with reference to the above descriptions.

[0481] Figures 26A to 26D The structure, material, etc. of the insulator 255 shown are the same as Figures 7A to 7D the structure, material, etc. of the insulator 255 shown. Therefore, the structure, material, etc. of the insulator 255 can be referred to the description of [Structure Example 1-4] above.

[0482] [Structure Example 2-5]

[0483] In Figures 26A to 26D the insulator 255 has a region located between the insulator 250 and the oxide semiconductor 230, but the present invention is not limited to this structure. For example, the insulator 255 may not have a region located between the insulator 250 and the oxide semiconductor 230.

[0484] Refer to Figures 27A to 27D Another example of the structure of a semiconductor device is described. Figures 27A to 27D It is a plan view and a cross-sectional view of a semiconductor device including a transistor 200A.

[0485] Figures 27A to 27D The main difference between the transistor 200A shown and Figures 26A to 26D the transistor 200A shown lies in the shapes of the insulator 255, the insulator 250, and the conductor 260. Hereinafter, parts that are repetitive of the above descriptions of [Structure Example 2-4], etc. are omitted with reference to the above descriptions.

[0486] Figures 27A to 27D The structure, material, etc. of the insulator 255 shown are the same as Figures 8A to 8D the structure, material, etc. of the insulator 255 shown. Figures 27A to 27D The structure, material, etc. of the insulator 250 shown are the same as Figures 8A to 8D the structure, material, etc. of the insulator 250 shown. Figures 27A to 27D The structure, material, etc. of the conductor 260 shown are the same as Figures 8A to 8DThe structure, materials, etc. of the conductor 260 shown are the same. Therefore, the structure, materials, etc. of the insulator 255, the insulator 250, and the conductor 260 can be referred to the description of the above [Structure Examples 1-5].

[0487] [Structure Example 2-6]

[0488] In Figures 14A to 14D , the oxide semiconductor 230 is provided on the insulator 223, but the present invention is not limited to this structure. For example, an insulator may be provided between the insulator 223 and the oxide semiconductor 230.

[0489] Refer to Figures 28A to 28D to illustrate another example of the structure of the semiconductor device. Figures 28A to 28D are a plan view and a cross-sectional view of a semiconductor device including a transistor 200A.

[0490] Figures 28A to 28D The transistor 200A shown includes an insulator 225 and is mainly different from the transistor 200A shown in Figures 14A to 14D in this regard. Hereinafter, the parts that are repeated with the description of the above [Structure Example 2-1] are omitted with reference to the above description.

[0491] Figures 28A to 28D The structure, materials, etc. of the insulator 225 shown are the same as those of the insulator 225 shown in Figures 9A to 9D Therefore, the structure, materials, etc. of the insulator 225 can be referred to the description of the above [Structure Examples 1-6].

[0492] Figures 28A to 28D The transistor 200A shown includes an insulator 225 on the insulators 223a, 223b, and 223c. In addition, it includes an oxide semiconductor 230 that is located on the insulators 223a, 223b, and 223c and covers the top surface and side surfaces of the insulator 225.

[0493] In Figures 28A to 28D the structure shown, one of the source region and the drain region is surrounded by the insulators 223a and 275 together with the insulator 225, and the other of the source region and the drain region is surrounded by the insulators 223b and 275 together with the insulator 225. In addition, one of the source region and the drain region is in contact with the insulators 223a, 225, and 275, and the other of the source region and the drain region is in contact with the insulators 223b, 225, and 275.

[0494] As Figure 28CAs shown, the insulator 250 has a structure that contacts a part of the top surface of the insulator 223c. At this time, the channel formation region and the insulator 225 are surrounded by the insulator 223c and the insulator 250. In addition, the channel formation region contacts the insulator 223c, the insulator 225, and the insulator 250.

[0495] <Modification Example 2>

[0496] Hereinafter, with reference to Figures 29A to 32D an example of a semiconductor device according to one aspect of the present invention will be described.

[0497] In Figures 29A to 32D the semiconductor devices shown in FIGS. A to D are different from the semiconductor device shown in Figures 14A to 14D in the shape of the insulator 223. Hereinafter, the parts different from the description of the above <Structural Example 2> will be mainly described, and the description of the repeated parts will be omitted with reference to the above description.

[0498] In addition, in the semiconductor devices shown in FIGS. A to D, the components having the same functions as the components constituting the semiconductor device shown in <Structural Example 2> are given the same reference numerals. Note that the materials constituting the semiconductor device in this section can be the materials described in detail in <Structural Example 2>.

[0499] [Modification Example 2-1]

[0500] Figures 29A to 29D Shows Figures 14A to 14E a modification example of the semiconductor device shown. Figures 29A to 29D is a plan view and a cross-sectional view of the semiconductor device.

[0501] In Figures 29A to 29D the semiconductor device shown, both the insulator 223a and the insulator 223b are processed into a strip shape, and the insulator 223c is processed into an island shape. For example, as Figure 29A and Figure 29B shown, both the insulator 223a and the insulator 223b are provided to extend in the channel length direction (A1 - A2 direction).

[0502] In addition, as Figure 29A and Figure 29D shown, the side ends on the A5 side of the insulator 223a, the insulator 223b, and the insulator 223c coincide with the side ends on the A5 side of the oxide semiconductor 230. In addition, the side ends on the A6 side of the insulator 223a, the insulator 223b, and the insulator 223c coincide with the side ends on the A6 side of the oxide semiconductor 230.

[0503] In the above structure, as Figure 29B and Figure 29DAs shown, the insulator 275 is disposed in contact with the top surface of the insulator 222, the top surface and side surfaces of the insulator 223a, the top surface and side surfaces of the insulator 223b, the side surface of the oxide semiconductor 230, the side surface and top surface of the conductor 242a, and the side surface and top surface of the conductor 242b. In this structure, the region 231a is surrounded by the insulator 223a and the insulator 275, and the region 231b is surrounded by the insulator 223b and the insulator 275.

[0504] Note that in Figure 29A and Figure 29D in the cross-section in the channel width direction, the side end portions of the insulators 223a, 223b, and 223c respectively coincide with the side end portions of the oxide semiconductor 230, but the present invention is not limited thereto. For example, in the cross-section in the channel width direction, the side end portions of the insulators 223a, 223b, and 223c respectively may be located outside the side end portions of the oxide semiconductor 230.

[0505] [Modification Example 2-2]

[0506] Figures 30A to 30D Shows Figures 14A to 14E a modification example of the semiconductor device shown. Figures 30A to 30D is a plan view and a cross-sectional view of the semiconductor device.

[0507] In Figures 30A to 30D the semiconductor device shown, the insulators 223a, 223b, and 223c are all processed into strip shapes. For example, as Figure 30A and Figure 30D shown, the insulators 223a, 223b, and 223c are all disposed to extend in the channel width direction (A3 - A4 direction). In addition, the insulators 223a, 223b, and 223c are all disposed to extend in the direction in which the conductor 260 extends.

[0508] In addition, as Figure 30A and Figure 30B shown, the side end portion of the insulator 223a on the A1 side coincides with the side end portion of the oxide semiconductor 230 on the A1 side. In addition, the side end portion of the insulator 223b on the A2 side coincides with the side end portion of the oxide semiconductor 230 on the A2 side.

[0509] In the above structure, as Figure 11B and Figure 11DAs shown, the insulator 275 is disposed in contact with the top surface of the insulator 222, the top surface and side surfaces of the insulator 223a, the top surface and side surfaces of the insulator 223b, the top surface of the insulator 223c, the side surface of the oxide semiconductor 230, the side surface and top surface of the conductor 242a, and the side surface and top surface of the conductor 242b. In this structure, the region 231a is surrounded by the insulator 223a and the insulator 275, and the region 231b is surrounded by the insulator 223b and the insulator 275.

[0510] Note that in Figure 30A and Figure 30B , in a cross-section in the channel length direction, the side ends of the insulator 223a and the insulator 223b respectively coincide with the side ends of the oxide semiconductor 230, but the present invention is not limited thereto. For example, in a cross-section in the channel length direction, the side ends of the insulator 223a and the insulator 223b may also be located outside the side ends of the oxide semiconductor 230.

[0511] [Modification Example 2-3]

[0512] Figures 31A to 31D Shows Figures 14A to 14E a modification example of the semiconductor device shown. Figures 31A to 31D is a plan view and a cross-sectional view of the semiconductor device.

[0513] In Figures 31A to 31D the semiconductor device shown, the insulators 223a, 223b, and 223c are all processed into island shapes. In addition, as Figures 31A to 31D shown, the side ends of the insulators 223a, 223b, and 223c respectively coincide with the side ends of the oxide semiconductor 230.

[0514] In the above structure, as Figures 31B to 31D shown, the insulator 275 is disposed in contact with the top surface of the insulator 222, the side surfaces of the insulator 223a, the side surfaces of the insulator 223b, the side surface of the oxide semiconductor 230, the side surface and top surface of the conductor 242a, and the side surface and top surface of the conductor 242b. In this structure, the region 231a is surrounded by the insulator 223a and the insulator 275, and the region 231b is surrounded by the insulator 223b and the insulator 275.

[0515] Note that Figure 31A and Figure 31BA structure is shown in which the side ends of the insulators 223a and 223b respectively coincide with the side ends of the oxide semiconductor 230, but the present invention is not limited thereto. For example, in a cross-section in the channel length direction, the side ends of the insulators 223a and 223b may also be located outside the side ends of the oxide semiconductor 230. In addition, in a cross-section in the channel width direction, the side ends of the insulators 223a and 223b may also be located outside the side ends of the oxide semiconductor 230.

[0516] In addition, as described in [Modification Example 1-3], for example, an insulator may be provided between the insulator 222 and the insulator 223. As an example, as Figures 32A to 32D shown, an island-shaped insulator 221 may be provided between the insulator 222 and the insulator 223.

[0517] Figures 32A to 32D The structure and material of the insulator 221 shown are the same as those of the insulator 221 shown in Figures 13A to 13D Therefore, the structure and material of the insulator 221 can be referred to the description of the above [Modification Example 1-3].

[0518] In Figures 29A to 32D the structures of the structures on the insulators 222 and 223 of the semiconductor devices shown as A to D in each figure are the same as those of the semiconductor devices shown in Figures 14A to 14D but the present invention is not limited thereto. The structures of the structures on the insulators 222 and 223 of the semiconductor devices shown as A to D in each figure may also be the same as those of the semiconductor devices shown in any one of Figures 23A to 28D

[0519] In addition, similar to the semiconductor device shown in Figures 24A to 24D the semiconductor devices shown as A to D in each figure may also include a conductor 215 and an insulator 216 below the insulator 222.

[0520] According to one aspect of the present invention, a semiconductor device including a transistor with less non-uniformity in electrical characteristics can be provided. In addition, a semiconductor device including a transistor with a large on-state current can be provided. In addition, a semiconductor device presenting good electrical characteristics can be provided. In addition, a semiconductor device with high reliability can be provided. In addition, a novel semiconductor device can be provided.

[0521] This embodiment can be appropriately combined with other embodiments. In addition, in this specification, when multiple structural examples are shown in one embodiment, the structural examples can be appropriately combined. ​

[0522] (Embodiment 2)

[0523] In this embodiment, Figures 33A to 50D a structural example of a semiconductor device according to one aspect of the present invention will be described. A semiconductor device according to one aspect of the present invention includes a transistor.

[0524] In Figures 33A to 50D the semiconductor device shown, the same reference numerals are given to the components having the same functions as those of the semiconductor device shown in Embodiment 1. Note that, in this embodiment, the materials described in detail in Embodiment 1 can also be used as the materials constituting the semiconductor device.

[0525] In Figures 33A to 33D , Figures 37A to 37D , Figures 41A to 41D and Figures 46A to 46D in each of FIGS. A shows a plan view of the semiconductor device. In addition, each FIG. B is a cross-sectional view corresponding to the portion indicated by the dash-dotted line A1 - A2 in each FIG. A, and is also a cross-sectional view in the channel length direction of the transistor. In addition, each FIG. C is a cross-sectional view corresponding to the portion indicated by the dash-dotted line A3 - A4 in each FIG. A, and is also a cross-sectional view in the channel width direction of the transistor. Each FIG. D is a cross-sectional view corresponding to the portion indicated by the dash-dotted line A5 - A6 in each FIG. A. Here, the dash-dotted line A1 - A2 is orthogonal to the dash-dotted lines A3 - A4 and A5 - A6, and the dash-dotted lines A3 - A4 and A5 - A6 are parallel to each other. For clarity, some components are omitted in the plan view of each FIG. A.

[0526] <Structural Example of Semiconductor Device>

[0527] Using Figures 33A to 35B an example of the structure of the semiconductor device will be described. Figures 33A to 33D are a plan view and a cross-sectional view of a semiconductor device including a transistor 200. In addition, Figure 34A and Figure 34B show enlarged cross-sectional views in the channel length direction of the transistor 200, Figure 35A and Figure 35B show enlarged cross-sectional views in the channel width direction of the transistor 200.

[0528] Figures 33A to 33D The structure of the semiconductor device shown in

[0529] The transistor 200 includes an insulator 216 on an insulator 214, a conductor 215 disposed in an embedded manner in the insulator 216, an insulator 222 on the insulator 216 and the conductor 215, an insulator 223 on the insulator 222, an oxide semiconductor 230 on the insulator 223, conductors 242a and 242b on the oxide semiconductor 230, an insulator 271a on the conductor 242a, an insulator 271b on the conductor 242b, an insulator 250 on the oxide semiconductor 230, and a conductor 260 on the insulator 250.

[0530] An insulator 275 is provided on the insulators 271a and 271b, and an insulator 280 is provided on the insulator 275. The insulator 250 and the conductor 260 are embedded inside an opening portion in the insulators 280 and 275. An insulator 282 is provided on the insulators 280, 250, and the conductor 260. Further, an insulator 283 is provided on the insulator 282.

[0531] The oxide semiconductor 230 has a region serving as a channel formation region of the transistor 200. The conductor 260 has a region serving as a first gate electrode (upper gate electrode) of the transistor 200. The insulator 250 has a region serving as a first gate insulator of the transistor 200. In addition, the conductor 215 has a region serving as a second gate electrode (lower gate electrode) of the transistor 200. Both the insulators 223 and 222 have a region serving as a second gate insulator of the transistor 200. The conductor 242a has a region serving as one of a source electrode and a drain electrode of the transistor 200. The conductor 242b has a region serving as the other of the source electrode and the drain electrode of the transistor 200.

[0532] As Figure 33B shown, in a cross section of the transistor 200, preferably, one side end portion of the conductor 242a substantially coincides with one side end portion of the oxide semiconductor 230, and one side end portion of the conductor 242b substantially coincides with the other side end portion of the oxide semiconductor 230. To achieve such a structure, it is preferable to process the oxide semiconductor 230 and the conductive layers that become the conductors 242a and 242b together into an island shape. Thereby, a semiconductor device of one mode of the present invention can be manufactured with good productivity. When processing is performed as described above, the side end portions of the oxide semiconductor 230, the conductor 242a, and the conductor 242b all coincide as described above.

[0533] In addition, the insulators 271a and 271b are used as an etch stop layer for protecting the conductors 242a and 242b in the above-described island-shaped processing. Therefore, as Figure 33A and Figure 33BAs shown, in the cross-section of the transistor 200, preferably, the side ends of the insulator 271a coincide with the side ends of the conductor 242a, and the side ends of the insulator 271b coincide with the side ends of the conductor 242b.

[0534] The oxide semiconductor 230 preferably includes an oxide semiconductor 230a on the insulator 223 and an oxide semiconductor 230b on the oxide semiconductor 230a. When the oxide semiconductor 230a is included under the oxide semiconductor 230b, diffusion of impurities from the structure formed under the oxide semiconductor 230a into the oxide semiconductor 230b can be suppressed.

[0535] This embodiment shows an example in which the oxide semiconductor 230 has a two-layer structure of the oxide semiconductor 230a and the oxide semiconductor 230b, but is not limited thereto. The oxide semiconductor 230 may have, for example, a single-layer structure of the oxide semiconductor 230b or a stacked structure of three or more layers.

[0536] In the oxide semiconductor 230b, a channel formation region of the transistor 200 and a source region and a drain region provided so as to sandwich the channel formation region are formed. At least a part of the channel formation region overlaps with the conductor 260. The source region overlaps with the conductor 242a, and the drain region overlaps with the conductor 242b. Note that the source region and the drain region may be swapped.

[0537] In addition, the channel formation region, the source region, and the drain region may be formed not only in the oxide semiconductor 230b but also in the oxide semiconductor 230a.

[0538] In addition, in the oxide semiconductor 230, it is sometimes difficult to clearly detect the boundaries of the respective regions. The concentrations of metal elements and impurity elements such as hydrogen and nitrogen detected in the respective regions not only change stepwise for each region, but may also change gradually in each region. That is, the concentration of impurity elements such as hydrogen and nitrogen may be lower in the region closer to the channel formation region.

[0539] The insulator 250 preferably has a function of capturing and fixing hydrogen. Thereby, the hydrogen concentration in the channel formation region of the oxide semiconductor 230b can be reduced. Therefore, V O H can be reduced to make the channel formation region i-type or substantially i-type.

[0540] As Figure 34A and Figure 35AAs shown, the insulator 250 preferably has a stacked structure including an insulator 250a in contact with the oxide semiconductor 230, an insulator 250b on the insulator 250a, and an insulator 250c on the insulator 250b. At this time, the insulator 250a preferably has a function of capturing and fixing hydrogen.

[0541] In addition, the insulator 250a is preferably made of a high dielectric constant (high-k) material. When a high-k material is used as the insulator 250a, the gate potential applied during transistor operation can be reduced while maintaining the physical thickness of the gate insulator. In addition, the equivalent oxide thickness (EOT) of the insulator used as the gate insulator can be reduced.

[0542] Next, as the insulator 250b, an insulator having a thermally stable structure such as silicon oxide or silicon oxynitride is preferably used.

[0543] In addition, as shown in Figure 34B and Figure 35B an insulator 250d may be provided between the insulator 250b and the insulator 250c. In this case, an insulator that can be used for the insulator 250a may be provided as the insulator 250d. For example, an insulator having a function of capturing and fixing hydrogen may be used as the insulator 250d. Thereby, hydrogen in the insulator 250b or the like can be captured and fixed more effectively. In addition, for example, a high dielectric constant (high-k) material may be used as the insulator 250d. Thereby, the gate potential applied during transistor operation can be reduced while maintaining the physical thickness of the gate insulator. In addition, the equivalent oxide thickness (EOT) of the insulator used as the gate insulator can be reduced.

[0544] The insulator 250d corresponds to the insulator provided between the insulator 250b and the insulator 250c described in Embodiment 1. Therefore, the materials and structures of the insulator 250d can refer to the content of the insulator provided between the insulator 250b and the insulator 250c described in Embodiment 1.

[0545] To suppress the oxidation of the conductors 242a, 242b, and 260, an oxygen barrier insulator is preferably provided near each of the conductors 242a, 242b, and 260. In the semiconductor device described in this embodiment, as the insulator provided near each of the conductors 242a, 242b, and 260, for example, the insulator 250a, the insulator 250c, the insulator 250d, and the insulator 275 can be cited.

[0546] The insulator 250a preferably has an oxygen barrier property. The insulator 250a is preferably at least less permeable to oxygen than the insulator 280. By adopting such a structure, oxidation of the sides of the conductors 242a and 242b can be suppressed, and an oxide film can be prevented from forming on the sides. As a result, a decrease in the on-state current or a decrease in the field-effect mobility of the transistor 200 can be suppressed.

[0547] In addition, by adopting the above structure, detachment of oxygen from the channel formation region of the oxide semiconductor 230b during heat treatment or the like can be suppressed. Therefore, formation of oxygen vacancies in the oxide semiconductor 230b can be suppressed.

[0548] In addition, by adopting the above structure, even if the insulator 280 contains an excessive amount of oxygen, excessive supply of the oxygen to the oxide semiconductor 230b can be suppressed, and an appropriate amount of oxygen can be supplied to the oxide semiconductor 230b. As a result, a decrease in the on-state current or a decrease in the field-effect mobility of the transistor 200 due to excessive oxidation of the source region and the drain region can be suppressed.

[0549] The insulator 250c preferably has an oxygen barrier property. As a result, diffusion of oxygen in the channel formation region of the oxide semiconductor 230 into the conductor 260 can be suppressed, and oxygen vacancies can be prevented from forming in the channel formation region. In addition, diffusion of oxygen in the oxide semiconductor 230 and oxygen in the insulator 280 into the conductor 260 can be suppressed, and oxidation of the conductor 260 can be prevented.

[0550] In addition, the insulator 250c preferably has a hydrogen barrier property. As a result, diffusion of impurities such as hydrogen in the conductor 260 into the oxide semiconductor 230b can be prevented.

[0551] The insulator 275 preferably has an oxygen barrier property. As a result, diffusion of oxygen in the insulator 280 into the conductors 242a and 242b can be suppressed. Therefore, oxidation of the conductors 242a and 242b caused by oxygen in the insulator 280 can be suppressed, an increase in the resistivity can be prevented, and a decrease in the on-state current can be suppressed.

[0552] In order to suppress a decrease in the hydrogen concentration in the source region and the drain region of the oxide semiconductor 230, it is preferable to provide a hydrogen barrier insulator near the source region and near the drain region. In the semiconductor device described in this embodiment, as the insulator provided near each of the source region and the drain region, for example, the insulator 275 can be cited.

[0553] The insulator 275 preferably has a hydrogen barrier property. As a result, diffusion of hydrogen in the source region and the drain region of the oxide semiconductor 230 to the outside can be suppressed, and a decrease in the hydrogen concentration in the source region and the drain region can be suppressed. Therefore, the source region and the drain region can be made n-type.

[0554] By adopting the above structure, the channel formation region can be made i-type or substantially i-type and the source region and the drain region can be made n-type, whereby a semiconductor device having good electrical characteristics can be provided. By adopting the above structure, even if the semiconductor device is miniaturized or highly integrated, it can have good electrical characteristics. In addition, by miniaturizing the transistor 200, the high-frequency characteristics can be improved. Specifically, the cut-off frequency can be increased.

[0555] Insulators 250a to 250d are used as part of the first gate insulator. Insulators 250a to 250d and the conductor 260 are disposed inside an opening formed in the insulator 280 or the like. In order to miniaturize the transistor 200, the thicknesses of insulators 250a to 250d are preferably small. The thicknesses of insulators 250a to 250d are all preferably 0.1 nm or more and 10 nm or less, more preferably 0.1 nm or more and 5.0 nm or less, further preferably 0.5 nm or more and 5.0 nm or less, still further preferably 1.0 nm or more and less than 5.0 nm, and even more preferably 1.0 nm or more and 3.0 nm or less. In addition, at least a part of insulators 250a to 250c may have a region with the above thickness.

[0556] In order to reduce the thicknesses of insulators 250a to 250d as described above, deposition is preferably performed by the ALD method.

[0557] Note that in the above, it is described that the insulator 250 has a three-layer structure of insulators 250a to 250c or a four-layer structure of insulators 250a to 250d, but the present invention is not limited thereto. The insulator 250 may have a structure including at least one of insulators 250a to 250d. By forming the insulator 250 of one, two, or three layers of insulators 250a to 250d, the manufacturing process of the semiconductor device can be simplified, whereby the productivity can be improved.

[0558] In this embodiment, preferably, the semiconductor device has a structure for suppressing hydrogen from mixing into the transistor 200 or the like in addition to the above structure. For example, preferably, an insulator having a function of suppressing hydrogen diffusion is provided so as to cover one or both of the upper and lower sides of the transistor 200 or the like. In the semiconductor device described in this embodiment, examples of such an insulator include the insulator 214, the insulator 282, and the insulator 283. In addition, the insulator 214 provided under the transistor 200 may have the same structure as one or both of the insulator 282 and the insulator 283. In this case, the insulator 214 may adopt a laminated structure of the insulator 282 and the insulator 283, a structure in which the insulator 282 is located below and the insulator 283 is located above, or a structure in which the insulator 282 is located above and the insulator 283 is located below.

[0559] One or more of the insulator 214, the insulator 282, and the insulator 283 are preferably used as a barrier insulator for suppressing the diffusion of impurities such as water and hydrogen from the substrate side or above the transistor 200 or the like to the transistor 200 or the like. Therefore, one or more of the insulator 214, the insulator 282, and the insulator 283 preferably contain an insulating material having a function of suppressing the diffusion of hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N 2 O, NO, NO 2 etc.), copper atoms and other impurities (not easily permeable to the above impurities). In addition, it preferably includes an insulating material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) (not easily permeable to the above oxygen).

[0560] As the insulators 214, 282, and 283, it is preferable to use insulators having a function of suppressing the diffusion of impurities such as water and hydrogen and oxygen. For example, the insulator 283 preferably has high hydrogen barrier properties. In addition, for example, the function of the insulator 282 to capture and fix hydrogen is preferably high. Thereby, diffusion of impurities such as water and hydrogen from an interlayer insulating film or the like disposed above the insulator 283 into the transistor 200 or the like can be suppressed. In addition, hydrogen in the insulators 280 and 250 or the like can be captured and fixed to the insulator 282. In addition, diffusion of oxygen in the insulator 280 or the like into the region above the transistor 200 or the like can be suppressed. In addition, by adopting the same structure as one or both of the insulator 282 and the insulator 283 for the insulator 214, diffusion of impurities such as water and hydrogen from the substrate side into the transistor 200 or the like can be suppressed. In addition, diffusion of oxygen in the oxide semiconductor 230 or the like into the region below the transistor 200 or the like can be suppressed. In this way, by adopting a structure in which the transistor 200 or the like is surrounded by insulators having a function of suppressing the diffusion of impurities such as water and hydrogen and oxygen, diffusion of an excessive amount of oxygen and hydrogen into the oxide semiconductor can be suppressed. Thereby, improvement in the electrical characteristics and reliability of the semiconductor device can be achieved.

[0561] The conductor 215 is disposed so as to overlap with the oxide semiconductor 230 and the conductor 260. Here, the conductor 215 is preferably disposed so as to be embedded in an opening formed in the insulator 216. In addition, as Figure 33A and Figure 33C shown, the conductor 215 is preferably disposed so as to extend in the channel width direction. By adopting such a structure, the conductor 215 is used as a wiring when a plurality of transistors are provided.

[0562] The conductor 215 may have a single-layer structure or a stacked structure. In Figure 33B etc., the conductor 215 includes a conductor 215a and a conductor 215b. The conductor 215a is disposed so as to be in contact with the bottom surface and the side wall of the above-described opening. The conductor 215b is disposed so as to be embedded in a concave portion of the conductor 215a formed along the above-described opening. Here, the height of the top surface of the conductor 215 is the same as the height of the top surface of the insulator 216.

[0563] The insulator 222 is preferably a hydrogen barrier insulator. In addition, as the insulator 222, an oxygen barrier insulator is preferably used. For example, compared with the insulator 216, the insulator 222 preferably has a function of suppressing the diffusion of one or both of hydrogen and oxygen.

[0564] When forming the insulator 222 using this material, the insulator 222 is used as a layer that suppresses the release of oxygen from the oxide semiconductor 230 to the substrate side and the diffusion of impurities such as hydrogen from the peripheral portion of the transistor 200 into the oxide semiconductor 230. Therefore, by providing the insulator 222, the diffusion of impurities such as hydrogen into the inside of the transistor 200 can be suppressed, and the generation of oxygen vacancies in the oxide semiconductor 230 can be suppressed. In addition, the reaction between the conductor 215 and the oxygen contained in the oxide semiconductor 230 can be suppressed.

[0565] In addition, the insulator 222 may also have a single-layer structure or a stacked structure of an insulator containing a high-k material. When miniaturizing and highly integrating transistors, due to the thinning of the gate insulator, problems such as leakage current sometimes occur. By using a high-k material as the insulator used as the gate insulator, the gate potential during transistor operation can be reduced while maintaining the physical thickness.

[0566] Each of the conductor 242a and the conductor 242b can have either a single-layer structure or a stacked structure. In addition, the conductor 260 can have either a single-layer structure or a stacked structure.

[0567] For example, as Figure 34B shown, both the conductor 242a and the conductor 242b can have a two-layer structure. In this case, the conductor 242a is a stacked film of the conductor 242a1 and the conductor 242a2 on the conductor 242a1, and the conductor 242b is a stacked film of the conductor 242b1 and the conductor 242b2 on the conductor 242b1. At this time, as the layers in contact with the oxide semiconductor 230b (the conductor 242a1 and the conductor 242b1), a conductive material that is not easily oxidized such as a metal nitride or a conductive material having a function of suppressing oxygen diffusion is preferably used. Thereby, the conductor 242a and the conductor 242b can be prevented from being excessively oxidized due to the oxygen in the oxide semiconductor 230b. Thereby, a decrease in the conductivity of the conductor 242a and the conductor 242b can be suppressed.

[0568] In addition, the conductor 242a2 and the conductor 242b2 are preferably conductors such as metal layers having higher conductivity than the conductor 242a1 and the conductor 242b1. For example, the thickness of the conductor 242a2 and the conductor 242b2 is preferably larger than the thickness of the conductor 242a1 and the conductor 242b1. A conductor that can be used for the conductor 215b can be used as the conductor 242a2 and the conductor 242b2. Thereby, the conductor 242a and the conductor 242b can be used as wirings or electrodes having high conductivity. In this way, a semiconductor device can be provided in which the conductor 242a and the conductor 242b used as wirings or electrodes are provided in contact with the top surface of the oxide semiconductor 230 used as the active layer.

[0569] Both the insulator 271a and the insulator 271b are inorganic insulators that protect the conductors 242a and 242b. In addition, the insulator 271a and the insulator 271b are preferably inorganic insulators that are not easily oxidized to the conductors 242a and 242b because they are in contact with the conductors 242a and 242b, respectively. Therefore, preferably, the insulator 271a has a laminated structure of an insulator 271a1 and an insulator 271a2 on the insulator 271a1, and the insulator 271b has a laminated structure of an insulator 271b1 and an insulator 271b2 on the insulator 271b1. Here, the nitride insulator that can be used for the insulator 250c is preferably used for the insulator 271a1 and the insulator 271b1 so that the conductors 242a and 242b are not easily oxidized. In addition, the oxide insulator that can be used for the insulator 250b is preferably used for the insulator 271a2 and the insulator 271b2.

[0570] Here, the insulator 271a1 contacts the top surface of the conductor 242a and a part of the insulator 275, and the insulator 271b1 contacts the top surface of the conductor 242b and a part of the insulator 275. In addition, the insulator 271a2 contacts the top surface of the insulator 271a1 and the bottom surface of the insulator 275, and the insulator 271b2 contacts the top surface of the insulator 271b1 and the bottom surface of the insulator 275. For example, silicon nitride can be used as the insulator 271a1 and the insulator 271b1, and silicon oxide can be used as the insulator 271a2 and the insulator 271b2.

[0571] The insulating layers that become the insulator 271a and the insulator 271b are used as masks for the conductive layers that become the conductors 242a and 242b. Therefore, the conductive layer does not have a curved surface between the side surface and the top surface. As a result, the end where the side surface and the top surface of the conductor 242a and the conductor 242b intersect has an edge. When the end where the side surface and the top surface of the conductor 242a and the conductor 242b intersect has an edge, the cross-sectional area of the conductor 242a and the conductor 242b is larger than the case where the end has a curved surface. Furthermore, by using a nitride insulator that is not easily oxidized as the insulator 271a1 and the insulator 271b1, the conductors 242a and 242b can be prevented from being over-oxidized. As a result, the resistance of the conductors 242a and 242b is reduced, so the on-state current of the transistor can be increased.

[0572] As Figure 34A and Figure 35AAs shown, the conductor 260 is disposed inside the openings formed in the insulator 280, the insulator 275, and the insulator 223. Inside the openings, the conductor 260 is disposed so as to cover the top surface of the insulator 222, the side surface of the insulator 223, the side surfaces of the oxide semiconductors 230a and 230b, and the top surface of the oxide semiconductor 230b with the insulator 250 interposed therebetween. In addition, the height of the top surface of the conductor 260 is the same as the height of the top surface of the insulator 250 and the height of the top surface of the insulator 280.

[0573] As Figure 33C , Figure 35A and Figure 35B shown, the conductor 260 is preferably disposed to extend in the channel width direction. By adopting such a structure, the conductor 260 is used as a wiring when a plurality of transistors are provided.

[0574] In the case of adopting the above structure, as Figure 35A and Figure 35B shown, in the cross section in the channel width direction of the transistor 200, a curved surface may be provided between the side surface and the top surface of the oxide semiconductor 230b. That is, the end of the side surface and the end of the top surface may also be curved (hereinafter, also referred to as circular).

[0575] The radius of curvature of the above curved surface is preferably greater than 0 nm and less than the thickness of the oxide semiconductor 230b in the region overlapping with the conductor 242a or the conductor 242b or less than half the length of the region without the above curved surface. Specifically, the radius of curvature of the above curved surface is greater than 0 nm and 20 nm or less, preferably 1 nm or more and 15 nm or less, and more preferably 2 nm or more and 10 nm or less. By adopting the above shape, the coverage of the insulator 250 and the conductor 260 to the oxide semiconductor 230b can be improved.

[0576] In Figure 33B etc., the conductor 260 has a two-layer structure. Here, the conductor 260 preferably includes a conductor 260a and a conductor 260b disposed on the conductor 260a. For example, the conductor 260a is preferably disposed so as to surround the bottom surface and the side surface of the conductor 260b. At this time, as the conductor 260a, a conductive material that is not easily oxidized or a conductive material having a function of suppressing oxygen diffusion is preferably used.

[0577] The dielectric constants of the insulator 216 and the insulator 280 are preferably lower than that of the insulator 214. By using a material with a low dielectric constant for the interlayer film, the parasitic capacitance generated between wirings can be reduced. In addition, the top surfaces of the insulator 216 and the insulator 280 may also be flattened.

[0578] The concentration of impurities such as water and hydrogen in the insulator 280 is preferably reduced. For example, the insulator 280 preferably contains silicon-containing oxides such as silicon oxide and silicon oxynitride.

[0579] Note that, in the Figures 33A to 33D semiconductor device shown, the structure of the insulator 223 is the same as that of the insulator 223 in the Figures 5A to 5D semiconductor device shown, but the present invention is not limited thereto. The structure of the insulator 223 can be any of the structures of the insulator 223 described in Embodiment 1. As an example, as Figures 36A to 36D shown, the insulator 223 can also be the Figures 24A to 24D insulator 223 (insulators 223a to 223c) shown.

[0580] <Example of the structure of a semiconductor device 2>

[0581] In the Figures 33A to 33D , in the openings provided in the insulator 280, insulator 275, and insulator 223, the insulator 250 is in contact with the side surfaces of the insulator 280, insulator 275, and insulator 223, but the present invention is not limited to this structure. For example, in this opening, an insulator can also be provided between the insulator 250 and the insulator 280, insulator 275, and insulator 223.

[0582] Refer to Figures 37A to 39C to describe another example of the structure of a semiconductor device. Figures 37A to 37D is a plan view and a cross-sectional view of a semiconductor device including a transistor 200. In addition, Figures 38A to 39C shows an enlarged cross-sectional view in the channel length direction of the transistor 200.

[0583] Figures 37A to 37D The structure of the semiconductor device shown is also the detailed structure of the semiconductor device described in [Structure Examples 1-4] of the above Embodiment 1. Hereinafter, mainly the parts different from the description of [Structure Examples 1-4] of the above Embodiment 1 will be described, and the description of the repeated parts will be sometimes omitted with reference to the above description. For example, the materials and structures of the components (insulators, oxide semiconductors, conductors, etc.) for constituting the semiconductor device can refer to the content described in Embodiment 1.

[0584] In addition, Figures 37A to 37D the transistor 200 shown is also a Figures 33A to 33D deformation example of the transistor 200 shown. Specifically, Figures 37A to 37D the transistor 200 shown includes an insulator 255, mainly in this respect it is different from Figures 33A to 33Dis different from the transistor 200 shown below. Hereinafter, mainly the parts different from the description of the above <Example 1 of the structure of a semiconductor device> will be described, and for the repeated parts, refer to the above description and sometimes the description will be omitted.

[0585] The transistor 200 includes an insulator 216 on an insulator 214, a conductor 215 disposed in a manner embedded in the insulator 216, an insulator 222 on the insulator 216 and the conductor 215, an insulator 223 on the insulator 222, an oxide semiconductor 230 on the insulator 223, conductors 242a and 242b on the oxide semiconductor 230, an insulator 271a on the conductor 242a, an insulator 271b on the conductor 242b, an insulator 250 on the oxide semiconductor 230, and a conductor 260 on the insulator 250. In addition, insulators 255 are provided between the conductors 242a2, the conductors 242b2, the insulator 271a, the insulator 271b, the insulator 275, and the insulator 280 and the insulator 250.

[0586] The insulator 255, the insulator 250, and the conductor 260 are disposed inside an opening provided in the insulator 280 and the insulator 275. In addition, an insulator 282 is provided on the insulator 280, the insulator 255, the insulator 250, and the conductor 260.

[0587] The conductor 242a has a stacked structure of a conductor 242a1 and a conductor 242a2 on the conductor 242a1, and the conductor 242b has a stacked structure of a conductor 242b1 and a conductor 242b2 on the conductor 242b1. The conductors 242a1 and 242b1 in contact with the oxide semiconductor 230b are preferably the above-mentioned conductors that are not easily oxidized. In addition, the conductors 242a2 and 242b2 are preferably conductors such as metal layers having higher conductivity than the conductors 242a1 and 242b1.

[0588] As Figure 38A shown, in a cross-section in the channel length direction of the transistor 200, the distance L2 between the conductors 242a1 and 242b1 is smaller than the distance L1 between the conductors 242a2 and 242b2. By adopting such a structure, the distance between the source and the drain can be further reduced and correspondingly the channel length can be reduced. Therefore, the frequency characteristics of the transistor 200 can be improved. Thus, by realizing miniaturization of the semiconductor device, a semiconductor device with improved operating speed can be provided.

[0589] The openings provided in insulator 280 and insulator 275 overlap with the region between conductor 242a2 and conductor 242b2. In addition, a part of conductor 242a1 and conductor 242b1 is formed to protrude inward of the above-mentioned opening. Thus, insulator 255 contacts the top surface of conductor 242a1, the top surface of conductor 242b1, the side surface of conductor 242a2, and the side surface of conductor 242b2 inside the above-mentioned opening. Further, insulator 250 contacts the top surface of oxide semiconductor 230 in the region between conductor 242a1 and conductor 242b1.

[0590] Here, as Figure 38A shown, insulator 250 preferably has a stacked structure including insulator 250a in contact with oxide semiconductor 230, insulator 250b on insulator 250a, and insulator 250c on insulator 250b. At this time, insulator 250a preferably has a function of capturing and fixing hydrogen.

[0591] In addition, as Figure 38C shown, a structure in which insulator 250d is provided between insulator 250b and insulator 250c may also be adopted. In this case, an insulator that can be used as insulator 250a may be provided as insulator 250d.

[0592] Insulator 250a and insulator 255 preferably have oxygen barrier properties. Insulator 250a and insulator 255 are preferably at least less permeable to oxygen than insulator 280. Insulator 250a has a region in contact with the side surfaces of conductor 242a1 and conductor 242b1. Insulator 255 has a region in contact with the top surfaces of conductor 242a1, conductor 242b1, conductor 242a2, and conductor 242b2. Insulator 250a contacts the top surface and side surfaces of insulator 255. When insulator 250a and insulator 255 have oxygen barrier properties, oxidation of the side surfaces of conductor 242a and conductor 242b can be suppressed, and an oxide film is not formed on the side surfaces. Therefore, a decrease in the on-state current or field-effect mobility of transistor 200 can be suppressed.

[0593] Further, by adopting the above structure, even if insulator 280 contains an excessive amount of oxygen, excessive supply of the oxygen to oxide semiconductor 230b can be suppressed, and an appropriate amount of oxygen can be supplied to oxide semiconductor 230b. Therefore, a decrease in the on-state current or field-effect mobility of transistor 200 due to excessive oxidation of the source region and drain region can be suppressed.

[0594] Note that in the above description, the insulator 250 has a three-layer structure of the insulators 250a to 250c or a four-layer structure of the insulators 250a to 250d, but the present invention is not limited thereto. The insulator 250 may have a structure including at least one of the insulators 250a to 250d. By forming the insulator 250 with one, two, or three layers of the insulators 250a to 250d, the manufacturing process of the semiconductor device can be simplified, thereby improving productivity.

[0595] For example, as Figure 38B shown, the insulator 250 may also have a two-layer structure. In this case, the insulator 250 preferably has a stacked structure of the insulator 250a and the insulator 250c on the insulator 250a. A high-k material can be used for at least one of the insulator 250a and the insulator 250c. Thereby, the equivalent oxide thickness (EOT) can be reduced while maintaining the thicknesses of the insulator 250a and the insulator 250c at a level that suppresses leakage current.

[0596] Herein, as Figure 38B shown, in the transistor 200 according to the present embodiment, regions overlapping with the insulator 250 in contact with the side surface of the conductor 242a1 and regions overlapping with the insulator 250 in contact with the side surface of the conductor 242b1 (hereinafter referred to as Loff regions) are formed in the oxide semiconductor 230b. The Loff regions do not overlap with the conductor 242a1 and the conductor 242b1, and do not appropriately overlap with the conductor 260 with the insulator 250 therebetween, and thus function like a resistor.

[0597] In Figure 38B the shown transistor 200, the insulator 250 is composed only of the insulator 250a and the insulator 250c, and the thicknesses of the insulator 250a and the insulator 250c can be formed thin as described above. For example, alumina is used as the insulator 250a and has a thickness of 2.0 nm, and silicon nitride is used as the insulator 250c and has a thickness of 1.5 nm, whereby the thickness of the insulator 250 can be set to 3.5 nm. By thinning the thickness of the insulator 250 in this way, the width of the Loff region can also be reduced. Therefore, the frequency characteristics of the transistor 200 can be improved to increase the operating speed of the semiconductor device according to one aspect of the present invention.

[0598] In addition, in the present embodiment, insulators 255 are provided between insulator 250 and conductor 242a and between insulator 250 and conductor 242b. Thus, the distances between conductor 260 and conductor 242a and between conductor 260 and conductor 242b can be increased by an amount equivalent to the thickness of insulator 255. Therefore, it is possible to reduce the thickness of insulator 250 while reducing the parasitic capacitance generated between conductor 260 and conductor 242a and conductor 242b, thereby reducing the Loff region.

[0599] As Figure 37B and Figure 37C shown, insulator 255 is disposed inside the opening formed in insulator 280 or the like, and in this opening, it contacts the side surfaces of insulator 280, insulator 275, insulator 271a, insulator 271b, conductor 242a2, conductor 242b2, conductor 242a1, conductor 242b1, and the top surface of insulator 222. In other words, it can also be said that insulator 255 forms an opening in the above-mentioned opening in such a way as to expose the island-shaped oxide semiconductor 230. In addition, in the region of the opening where insulator 255 is formed, insulator 250 contacts oxide semiconductor 230 and insulator 222. Note that in Figure 37C , insulator 255 includes an opening only near oxide semiconductor 230, but the present invention is not limited to this. Insulator 255 only needs to include an opening at least in the region where oxide semiconductor 230b is sandwiched between conductor 242a1 and conductor 242b1. Therefore, for example, insulator 255 can also be formed in a sidewall shape in the opening formed in insulator 280 or the like with almost no region in contact with insulator 222.

[0600] Insulator 255 is formed in contact with the side surfaces of conductor 242a2 and conductor 242b2 and is an inorganic insulator that protects conductor 242a2 and conductor 242b2. Since it is exposed to an oxidizing atmosphere, insulator 255 is preferably an inorganic insulator that is not easily oxidized. In addition, since insulator 255 contacts conductor 242a2 and conductor 242b2, it is preferably an inorganic insulator that does not easily oxidize conductor 242a2 and 242b2. Therefore, insulator 255 preferably uses an insulating material that can be used for insulator 250c having an oxygen barrier property. For example, silicon nitride can be used as insulator 255.

[0601] By using such an insulator 255, even if heat treatment is performed in an oxygen-containing atmosphere after conductor 242a2 and conductor 242b2 are separated and before insulator 250 is deposited, conductor 242a2 and conductor 242b2 can be prevented from being over-oxidized.

[0602] In addition, the thickness of the insulator 255 is preferably larger than any one of the insulators 250a to 250d. The thickness of the insulator 255 is preferably 1 nm or more and 20 nm or less, more preferably 1 nm or more and 15 nm or less, and still more preferably 3 nm or more and 10 nm or less. For example, it can be set to about 5 nm. When the insulator 255 has the above thickness, the distance between the conductor 260 and the conductor 242a or the conductor 242b can be increased to reduce the parasitic capacitance. Note that it is sufficient that at least a part of the insulator 255 has a region with the above thickness. In addition, since the insulator 255 is provided in the opening formed in the insulator 280, it is preferably deposited by a deposition method such as ALD with good coverage.

[0603] In addition, when separating the conductor 242a1 and the conductor 242b1, the insulator 255 is used as a part of the mask. Therefore, as Figure 37B shown, preferably, in the cross section of the transistor 200, the side end portions of the insulator 255 coincide with the side end portions of the conductor 242a1 and the side end portions of the conductor 242b1.

[0604] Here, in the conductor 242a1, the portion where the insulator 255 is formed on the top surface protrudes more toward the conductor 260 side than the conductor 242a2. Similarly, in the conductor 242b1, the portion where the insulator 255 is formed on the top surface protrudes more toward the conductor 260 side than the conductor 242b2. As Figure 38A shown, in the cross section in the channel length direction of the transistor 200, the distance L2 between the conductor 242a1 and the conductor 242b1 is smaller than the distance L1 between the conductor 242a2 and the conductor 242b2.

[0605] The distance L2 between the conductor 242a1 and the conductor 242b1 is preferably very small because it affects the channel length of the transistor 200. For example, the distance L2 is preferably 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less and 1 nm or more or 5 nm or more. For example, the distance L2 is more preferably about 2 nm or more and 20 nm or less. By adopting such a structure, the distance between the source and the drain can be further reduced and correspondingly the channel length can be reduced. Therefore, the frequency characteristics of the transistor 200 can be improved. Thus, by miniaturizing the semiconductor device, a semiconductor device with an increased operating speed can be provided.

[0606] In addition, in Figure 38A the transistor 200 shown, the opposite side surfaces of the conductor 242a1 and the conductor 242b1 are substantially perpendicular to the top surface of the oxide semiconductor 230b, but the present invention is not limited thereto. For example, asFigure 39A As shown, the opposing sides of the conductor 242a1 and the conductor 242b1 may also be in a conical shape. By adopting the above shape, near the side ends of the conductor 242a1 and the side ends of the conductor 242b1, the distance between the conductor 260 and the oxide semiconductor 230b becomes smaller, so the influence of the Loff region can be reduced.

[0607] In addition, as Figure 39B shown, the opposing sides of the conductor 242a1 and the conductor 242b1 may be in a conical shape. Moreover, the opposing sides of the conductor 242a2 and the conductor 242b2 may also be in a conical shape.

[0608] In addition, as Figure 39C shown, the cone angle of the conductor 242a1 may be made sharper than the cone angle of the conductor 242a2. In addition, the cone angle of the conductor 242b1 may be made sharper than the cone angle of the conductor 242b2. By adopting this shape, near the side ends of the conductor 242a1 and the side ends of the conductor 242b1, the distance between the conductor 260 and the oxide semiconductor 230b becomes smaller, so the influence of the Loff region can be reduced.

[0609] Note that in the semiconductor device shown in Figures 37A to 37D , the structure of the insulator 223 is the same as the structure of the insulator 223 in the semiconductor device shown in Figures 7A to 7D , but the present invention is not limited thereto. The structure of the insulator 223 may be any one of the structures of the insulator 223 described in Embodiment 1. As an example, as Figures 40A to 40D shown, the insulator 223 may also be the insulator 223 (insulators 223a to 223c) shown in Figures 26A to 26D .

[0610] <Structural Example 3 of Semiconductor Device>

[0611] Use Figures 41A to 44C to illustrate another example of the structure of a semiconductor device. Figures 41A to 41D is a plan view and a cross-sectional view of a semiconductor device including a transistor 200. In addition, Figure 42 A to Figure 44C show an enlarged cross-sectional view in the channel length direction of the transistor 200.

[0612] Figures 41A to 41DThe structure of the semiconductor device shown is also the detailed structure of the semiconductor device described in [Structure Examples 1-5] of the above-described Embodiment 1. Hereinafter, mainly the parts different from the description of [Structure Examples 1-5] of the above-described Embodiment 1 will be described, and the description of the repeated parts will be omitted with reference to the above description. For example, the materials and structures of the elements (insulators, oxide semiconductors, conductors, etc.) used to form the semiconductor device can be referred to the content described in Embodiment 1.

[0613] In addition, Figures 41A to 41D the transistor 200 shown is also Figures 37A to 37D a modified example of the transistor 200 shown. Specifically, Figures 41A to 41D the main difference between the transistor 200 shown and Figures 37A to 37D the transistor 200 shown lies in the shape of the insulator 255. Hereinafter, mainly the parts different from the description of <Structure Example 2 of the Semiconductor Device> above will be described, and the description of the repeated parts will be omitted with reference to the above description.

[0614] As Figure 42 shown, when viewed from the cross-section in the channel length direction of the transistor 200, the distance L2 between the conductor 242a1 and the conductor 242b1 is smaller than the distance L1 between the conductor 242a2 and the conductor 242b2. Specifically, the difference between the distance L1 and the distance L2 is equal to twice the thickness of the insulator 255. In other words, the distance L1 is equal to the distance L2 plus twice the thickness of the insulator 255. Here, the thickness of the insulator 255 refers to the thickness in the A1-A2 direction of at least a part of the insulator 255. By adopting such a structure, the distance between the source and the drain can be further reduced, and correspondingly, the channel length can be reduced. Therefore, the frequency characteristics of the transistor 200 can be improved. Thus, by miniaturizing the semiconductor device, a semiconductor device with improved operating speed can be provided.

[0615] The openings provided in the insulators 280 and 275 overlap with the region between the conductors 242a2 and 242b2. In a plan view, the side surfaces of the insulator 280 in the above-mentioned openings coincide with the side surfaces of the conductor 242a2 and the conductor 242b2. In addition, a part of the conductors 242a1 and 242b1 is formed to protrude inward of the above-mentioned opening. Here, a part of the top surface of the conductor 242a1 contacts the conductor 242a2, and a part of the top surface of the conductor 242b1 contacts the conductor 242b2. Therefore, the insulator 255 contacts the other part of the top surface of the conductor 242a1, the other part of the top surface of the conductor 242b1, the side surface of the conductor 242a2, and the side surface of the conductor 242b2 inside the above-mentioned opening. In addition, the insulator 250 contacts the top surface of the oxide semiconductor 230, the side surfaces of the conductors 242a1 and 242b1, and the side surface of the insulator 255.

[0616] The insulator 255 is formed in a sidewall shape by anisotropic etching so as to contact the sidewalls of the openings provided in the insulators 280, etc. (here, the sidewalls of the openings correspond to the side surfaces of the insulators 280, etc. in the openings). The insulator 255 is formed so as to contact the side surfaces of the conductor 242a2 and the conductor 242b2, and has the function of protecting the conductor 242a2 and the conductor 242b2.

[0617] Furthermore, in order to suppress the oxidation of the conductors 242a, 242b, and 260, it is preferable to provide an oxygen barrier insulator near each of the conductors 242a, 242b, and 260. In Figure 42 the semiconductor device shown, this insulator is, for example, the insulators 250a, 250c, 255, and 275. For example, each of the insulators 250a, 250c, 255, and 275 preferably adopts a single-layer structure or a stacked structure of an oxygen barrier insulator.

[0618] The insulator 250a and the insulator 255 preferably have oxygen barrier properties. The insulator 250a and the insulator 255 are preferably at least less permeable to oxygen than the insulator 280. The insulator 250a has a region in contact with the side surfaces of the conductor 242a1 and the conductor 242b1. The insulator 255 has regions in contact with the top surfaces of the conductor 242a1, the conductor 242b1, the conductor 242a2, and the conductor 242b2. The side surfaces of the insulator 250a and the insulator 255 are in contact with each other. When the insulator 250a and the insulator 255 have oxygen barrier properties, oxidation of the side surfaces of the conductor 242a and the conductor 242b can be suppressed, and an oxide film can be prevented from forming on these side surfaces. Therefore, a decrease in the on-state current or a decrease in the field-effect mobility of the transistor 200 can be suppressed.

[0619] Here, it is preferable that a region of the insulator 275 that does not overlap with the oxide semiconductor 230 is in contact with the insulator 223, a side end portion of the insulator 275 is in contact with the insulator 255, and upper end portions of the insulator 255 and the insulators 250a to 250c are in contact with the insulator 282. By adopting the above structure, in the region sandwiched between the insulator 283 and the insulator 222, the insulator 275 separates the insulator 280 from the oxide semiconductor 230, the insulator 255 and the insulator 250a separate the insulator 280 from the insulator 250b, the insulator 250c separates the conductor 260 from the insulator 250b, and the insulator 255 and the insulator 250a separate the conductor 242a2 and the conductor 242b2 from the insulator 250b.

[0620] Note that, in Figure 42 it is described that the insulator 250 has a three-layer structure of the insulators 250a to 250c, but the present invention is not limited thereto. The insulator 250 may have a structure including at least one of the insulators 250a to 250d. For example, in the same manner as the structure shown in Figure 38B , the insulator 250 may also have a two-layer structure. In this case, the insulator 250 preferably has a stacked structure of the insulator 250a and the insulator 250c on the insulator 250a (see Figure 43A ). Additionally, for example, in the same manner as the structure shown in Figure 38C , the insulator 250 may also have a four-layer structure. In this case, the insulator 250 preferably has a stacked structure of the insulator 250a, the insulator 250b on the insulator 250a, the insulator 250d on the insulator 250b, and the insulator 250c on the insulator 250d (see Figure 43B ).

[0621] As in Figure 41B and Figure 41CAs shown, the insulator 255 is disposed inside the middle of the opening formed in the insulator 280 or the like, and is in contact with the side surfaces of the insulator 280, the insulator 275, the insulator 271a, the insulator 271b, the side surface of the conductor 242a2, the side surface of the conductor 242b2, the top surface of the conductor 242a1, the top surface of the conductor 242b1, and the top surface of the insulator 222. In other words, it can also be said that the insulator 255 is formed in a sidewall shape so as to be in contact with the sidewalls of the opening formed in the insulator 280 or the like.

[0622] In addition, the thickness of the insulator 255 is preferably 0.5 nm or more and 20 nm or less, more preferably 0.5 nm or more and 10 nm or less, and still more preferably 0.5 nm or more and 3 nm or less. When the insulator 255 has the above thickness, over-oxidation of the conductor 242a2 and the conductor 242b2 can be suppressed. Note that it is sufficient that at least a part of the insulator 255 has a region with the above value as the thickness. In addition, since the insulator 255 is disposed so as to be in contact with the sidewalls of the opening formed in the insulator 280 or the like, it is preferably deposited by the ALD method or the like with good coverage. When the thickness of the insulator 255 is too large, the deposition time of the insulator 255 by the ALD method is long, resulting in a decrease in productivity. Therefore, the thickness of the insulator 255 is preferably set to the above range approximately.

[0623] In addition, the insulator 255 may have a laminated structure of two or more layers. In this case, as long as at least one layer is the above-mentioned inorganic insulator that is not easily oxidized. For example, as Figure 43C shown, a laminated structure of the insulator 255a and the insulator 255b on the insulator 255a may also be employed. In addition, it can also be regarded as a structure in which the insulator 255b is disposed inside the insulator 255a. Here, the bottom surface of the insulator 255b may sometimes be in contact with the insulator 255a. It is sufficient to use the above-mentioned inorganic insulator that is not easily oxidized for the insulator 255b, and the insulator (for example, silicon oxide or the like) that can be used for the insulator 250b for the insulator 255a. The insulator 255a preferably has a lower dielectric constant than the insulator 255b. In this way, by adopting a two-layer structure as the insulator 255 to increase the thickness, the distance between the conductor 260 and the conductor 242a or the conductor 242b can be increased to reduce the parasitic capacitance.

[0624] Note that Figure 43C shows a structure in which the insulator 255a is disposed on the outside and the insulator 255b is disposed on the inside, but the present invention is not limited thereto. For example, as Figure 43D shown, a structure in which the insulator 255b is disposed on the outside and the insulator 255a is disposed on the inside may also be employed. Here, the bottom surface of the insulator 255a may sometimes be in contact with the insulator 255b.

[0625] In addition, when the conductors 242a1 and 242b1 are separated, the insulator 255 is used as a mask. Therefore, as Figure 41B shown, in the cross-section of the transistor 200, the side ends of the insulator 255 preferably coincide with the side ends of the conductor 242a1 and the side ends of the conductor 242b1.

[0626] Here, in the conductor 242a1, the portion where the insulator 255 is formed on the top surface protrudes more toward the conductor 260 side than the conductor 242a2. Similarly, in the conductor 242b1, the portion where the insulator 255 is formed on the top surface protrudes more toward the conductor 260 side than the conductor 242b2. As Figure 42 shown, when viewed from the cross-section in the channel length direction of the transistor 200, the distance L2 between the conductors 242a1 and 242b1 is smaller than the distance L1 between the conductors 242a2 and 242b2. Specifically, the difference between the distance L1 and the distance L2 is consistent with twice the thickness of the insulator 255. In other words, the distance L1 is consistent with the distance L2 plus twice the thickness of the insulator 255.

[0627] As Figure 44A shown, sometimes recesses are formed in the portions of the oxide semiconductor 230b exposed from the conductors 242a1 and 242b1. In other words, on the top surface of the oxide semiconductor 230b, the height of the region sandwiched between the conductors 242a1 and 242b1 is sometimes lower than the regions overlapping with the conductor 242a1 and the region overlapping with the conductor 242b1.

[0628] In addition, in Figure 44A the transistor 200 shown, the opposing sides of the conductors 242a1 and 242b1 and the opposing sides of the conductors 242a2 and 242b2 are perpendicular or substantially perpendicular to the top surface of the oxide semiconductor 230b, but the present invention is not limited thereto. For example, as Figure 44B shown, the opposing sides of the conductors 242a1 and 242b1 and the opposing sides of the conductors 242a2 and 242b2 may also have a tapered shape. In this case, the sides of the conductors 242a2, 242b2, the insulators 271a, 271b, the insulator 275, and the insulator 280 may sometimes have a tapered shape.

[0629] In addition, the taper angles of the conductors 242a1 and 242b1 may be sharper than the taper angles of the conductors 242a2 and 242b2.

[0630] In addition, as Figure 44C shown, the upper part of the side surface of the insulator 255 may sometimes have a tapered shape. In addition, asFigure 44C As shown, sometimes a conical shape that is continuous or substantially continuous with the conical shape on the side of the insulator 255 is also formed on the upper part of the insulator 280. Additionally, as Figure 44C shown, sometimes both the upper part of the insulator 255 and the upper part of the insulator 280 have curved surfaces. Here, the insulator 250a sometimes contacts the conical-shaped portions of the upper parts of the insulator 255 and the insulator 280. At this time, when the upper parts of the insulator 255 and the insulator 280 have curved surfaces, the insulator 250a can be formed with high coverage.

[0631] Note that, in the semiconductor device shown in Figures 41A to 41D , the structure of the insulator 223 is the same as that of the insulator 223 in the semiconductor device shown in Figures 8A to 8D , but the present invention is not limited to this. The structure of the insulator 223 can be any of the structures of the insulator 223 described in Embodiment 1. As an example, as Figures 45A to 45D shown, the insulator 223 can also be the insulator 223 (insulators 223a to 223c) shown in Figures 27A to 27D .

[0632] <Structural Example 4 of Semiconductor Device>

[0633] Use Figures 46A to 49C to illustrate the structural example of the semiconductor device. Figures 46A to 46D are the plan view and cross-sectional view of a semiconductor device including the transistor 200a and the transistor 200b. Note that the transistor 200b has the same structure as the transistor 200a, so the components are attached with the same hatching as the transistor 200a without attaching symbols. Hereinafter, sometimes the transistor 200a and the transistor 200b are collectively referred to as the transistor 200. By providing a capacitor electrically connected to the transistor 200a and a capacitor electrically connected to the transistor 200b in the semiconductor device shown in this embodiment, it can be used as two 1T (transistor) 1C (capacitor) type memory cells and used in a storage device.

[0634] Additionally, Figure 47A shows an enlarged view of the vicinity of the conductor 260 in Figure 46B . Additionally, Figure 47B shows an enlarged view of the vicinity of the insulator 225 in Figure 46C . Additionally, Figure 49A shows an enlarged view of the vicinity of the conductor 242a in Figure 46B . Additionally, Figure 49B shows an enlarged view of the vicinity of the insulator 225 in Figure 46D .

[0635] Figures 46A to 46DThe structure of the semiconductor device shown is also the detailed structure of the semiconductor device described in [Structure Examples 1-6] of the above-described Embodiment 1. Hereinafter, mainly the parts different from the description of [Structure Examples 1-6] of the above-described Embodiment 1 will be described, and the description of the repeated parts will be referred to the above description and sometimes omitted. For example, the materials and structures of the constituent elements (insulators, oxide semiconductors, conductors, etc.) for constituting the semiconductor device can be referred to the content described in Embodiment 1.

[0636] In addition, Figures 46A to 46D the transistor 200 shown is also Figures 33A to 33D a modified example of the transistor 200 shown. Specifically, Figures 46A to 46D the transistor 200 shown includes an insulator 225 and does not have a conductor 215, an insulator 271a, and an insulator 271b, and is mainly different from the Figures 33A to 33D transistor 200 shown in this respect. In addition, Figures 46A to 46D the difference between the transistor 200 shown and the Figures 33A to 33D transistor 200 shown mainly lies in the shapes of the oxide semiconductor 230, the conductor 242a, and the conductor 242b. Hereinafter, mainly the parts different from the description of the above <Structure Example 1 of the Semiconductor Device> will be described, and the description of the repeated parts will be referred to the above description and sometimes omitted.

[0637] The transistor 200 includes an insulator 216 on an insulator 214, an insulator 222 on the insulator 216, an insulator 223 on the insulator 222, an insulator 225 on the insulator 223, an oxide semiconductor 230 on the insulator 225 and the insulator 223, a conductor 242a and a conductor 242b on the oxide semiconductor 230, an insulator 250 on the oxide semiconductor 230, and a conductor 260 on the insulator 250.

[0638] An insulator 275 is provided on the conductor 242a and the conductor 242b, and an insulator 280 is provided on the insulator 275. The insulator 250 and the conductor 260 are disposed inside the openings provided in the insulator 280 and the insulator 275. In addition, an insulator 282 is provided on the insulator 280, the insulator 250, and the conductor 260. In addition, an insulator 283 is provided on the insulator 282.

[0639] An insulator 241a is provided in contact with the inner wall of the opening provided in the insulator 280 or the like, and a conductor 240a is provided in contact with the side surface of the insulator 241a. The bottom surface of the conductor 240a is in contact with the top surface of the conductor 242a. An insulator 241b is provided in contact with the inner wall of the opening provided in the insulator 280 or the like, and a conductor 240b is provided in contact with the side surface of the insulator 241b. The bottom surface of the conductor 240b is in contact with the top surface of the conductor 242b.

[0640] The oxide semiconductor 230 has a region that serves as the channel formation region of the transistor 200. The conductor 260 has a region that serves as the gate electrode of the transistor 200b. The insulator 250 has a region that serves as the gate insulator of the transistor 200. The conductor 242a has a region that serves as one of the source electrode and the drain electrode of the transistor 200. The conductor 242b has a region that serves as the other of the source electrode and the drain electrode of the transistor 200. The conductor 240a and the conductor 240b are respectively used as plugs connected to the conductor 242a and the conductor 242b.

[0641] The oxide semiconductor 230 preferably includes an oxide semiconductor 230a covering the insulator 225 and an oxide semiconductor 230b on the oxide semiconductor 230a. Here, the oxide semiconductor 230a is in contact with the top surface and the side surface of the insulator 225 and the top surface of the insulator 223. As Figure 47B shown, etc., the oxide semiconductor 230a and the oxide semiconductor 230b are provided so as to cover the insulator 225 having a high aspect ratio. Therefore, the oxide semiconductor 230a and the oxide semiconductor 230b are preferably deposited by a deposition method with high coverage such as the ALD method. Here, as Figure 47B shown, in the cross-section in the channel width direction, the oxide semiconductor 230a and the oxide semiconductor 230b are formed in a folded state with the insulator 225 sandwiched therebetween. By adopting such a structure, the channel formation region of the transistor 200 can be formed on the top, the side surface on the A3 side, and the side surface on the A4 side of the insulator 225, so that the channel width per unit area can be increased.

[0642] This embodiment shows an example in which the oxide semiconductor 230 has a two-layer structure of the oxide semiconductor 230a and the oxide semiconductor 230b, but is not limited thereto. The oxide semiconductor 230 may have, for example, a single-layer structure of the oxide semiconductor 230b, or may have a stacked structure of three or more layers.

[0643] In Figure 47A and Figure 47BIn [the figure], the insulator 250 has a stacked structure including an insulator 250a in contact with the oxide semiconductor 230, an insulator 250b on the insulator 250a, an insulator 250d on the insulator 250b, and an insulator 250c on the insulator 250d.

[0644] For example, as Figure 48A shown, the insulator 250 may also have a two-layer structure. In this case, the insulator 250 preferably has a stacked structure including the insulator 250a and the insulator 250c on the insulator 250a. A high-k material may be used for at least one of the insulator 250a and the insulator 250c. Thereby, the equivalent oxide thickness (EOT) can be reduced while maintaining the thicknesses of the insulator 250a and the insulator 250c at a level that suppresses leakage current.

[0645] In addition, for example, as Figure 48B shown, the insulator 250 may also have a three-layer structure. In this case, the insulator 250 preferably has a stacked structure including the insulator 250a, the insulator 250b on the insulator 250a, and the insulator 250c on the insulator 250b.

[0646] The insulator 225 is formed in contact with the insulator 223. As Figure 47B and Figure 49B shown, in a cross-section in the channel width direction, the insulator 225 has a shape with a high aspect ratio. Here, the aspect ratio of the insulator 225 in the cross-section in the channel width direction refers to the ratio of the length L in the A3 - A4 direction of the insulator 225 (which may also be referred to as the width L of the insulator 225) to the length H in the direction perpendicular to the formation surface of the insulator 225 (e.g., the insulator 222) (which may also be referred to as the height H of the insulator 225). In the insulator 225, the height H of the insulator 225 is at least greater than the width L of the insulator 225. The height H of the insulator 225 may be greater than 1 times the width L of the insulator 225, preferably 2 times or more, more preferably 5 times or more, and further preferably 10 times or more. In addition, the height H of the insulator 225 is preferably 20 times or less the width L of the insulator 225.

[0647] The oxide semiconductor 230, the conductor 242a, and the conductor 242b are provided so as to cover the insulator 225 with such a high aspect ratio. In the transistor 200, as Figure 47BAs shown, an oxide semiconductor 230 is provided in a state of being folded in half with an insulator 225 sandwiched therebetween, and an insulator 250 and a conductor 260 are provided so as to cover the oxide semiconductor 230. Thus, in a cross section in the channel width direction, the oxide semiconductor 230 and the conductor 260 face each other with the insulator 250 interposed therebetween on the top, the side surface on the A3 side, and the side surface on the A4 side of the insulator 225. That is to say, the top, the side surface on the A3 side, and the side surface on the A4 side of the insulator 225 all serve as channel formation regions. Therefore, the channel width of the transistor 200 is larger than that in the case where the insulator 225 is not provided by the portions of the side surfaces on the A3 side and the A4 side of the insulator 225.

[0648] As described above, by increasing the channel width, the on-state current, field-effect mobility, frequency characteristics, etc. of the transistor 200 can be improved. Thereby, a semiconductor device with a high operating speed can be provided. In addition, the operating speed of a storage device using this semiconductor device can be increased. Further, in the above structure, by providing the insulator 225, the channel width can be increased without increasing the occupied area of the transistor 200. Thereby, miniaturization or high integration of the semiconductor device can be achieved. In addition, the storage capacity of a storage device using this semiconductor device can be increased.

[0649] The insulator 225 may use an insulating material that can be used for the insulator 222, the insulator 223, the insulator 280, or the insulator 250, etc. In addition, since the insulator 225 has a shape with a high aspect ratio, it is preferably formed in a sidewall shape on the side surface of the sacrificial layer. Therefore, the insulator 225 is preferably formed by the ALD method with high coverage. For example, the insulator 225 may use silicon nitride, hafnium oxide, etc. deposited by the ALD method.

[0650] In this way, by forming the sidewall-shaped insulator 225 in contact with the side surface of the sacrificial layer, as Figure 46A shown, etc., the insulator 225 of the transistor 200a and the insulator 225 of the transistor 200b can be formed simultaneously. By forming the two insulators 225 in this way, the distance between the two insulators 225 can be set according to the size of the sacrificial layer. Therefore, the distance between the insulators 225 can be reduced to reduce the occupied area of the transistor 200a and the transistor 200b, and thereby high integration of the semiconductor device can be achieved.

[0651] Note that the insulator 225 is not strictly limited to an insulating material. For example, a metal oxide with relatively high insulation may also be used. For example, the metal oxide that can be used for the oxide semiconductor 230a described above may also be used.

[0652] In addition, the top of the insulator 225 may also have a curved shape. When having such a curved shape, it is possible to prevent defects such as voids from forming in the oxide semiconductors 230a, 230b, the conductors 242a, and the conductors 242b near the top of the insulator 225. Note that Figure 47B and Figure 49B etc. show a symmetric structure in which both the A3 side (A5 side) and the A4 side (A6 side) of the top of the insulator 225 are provided with a curved shape, but the present invention is not limited thereto. For example, there may be an asymmetric structure in which a curved shape is provided only on the A3 side (A5 side) of the top of the insulator 225.

[0653] The conductors 242a and the conductors 242b are arranged separately from each other and are provided in contact with the oxide semiconductor 230b. As Figure 49A and Figure 49B etc. show, the conductors 242a and the conductors 242b are provided so as to cover the insulator 225 having a high aspect ratio. Therefore, the conductors 242a and the conductors 242b are preferably deposited by a deposition method with high coverage such as the ALD method or the CVD method.

[0654] Here, near the source or drain of the transistor 200a, as Figure 49B shows, the oxide semiconductor 230 and the conductor 242b are provided in a state of being folded with the insulator 225 interposed therebetween. Thus, in a cross-section in the channel width direction, the conductor 242b is in contact with the oxide semiconductor 230b at the top of the insulator 225, the side surface on the A5 side, and the side surface on the A6 side. Therefore, the contact area between the conductor 242b and the oxide semiconductor 230b is larger than that in the case where the insulator 225 is not provided by the portions of the side surfaces on the A5 side and the A6 side of the insulator 225. Note that Figure 49B shows near the conductor 242b, but the same applies to the conductor 242a. That is, the contact area between the conductor 242a and the oxide semiconductor 230b increases in the same manner as the above-mentioned conductor 242b and the oxide semiconductor 230b.

[0655] As described above, when the contact area between the conductor 242a or the conductor 242b and the oxide semiconductor 230b increases, the on-state current, frequency characteristics, etc. of the transistor 200 can be improved without increasing the occupied area of the transistor 200. Thereby, a semiconductor device with a high operating speed can be provided. In addition, the operating speed of a storage device using the semiconductor device can be increased. Thereby, miniaturization or high integration of the semiconductor device can be achieved. In addition, the storage capacity of a storage device using the semiconductor device can be increased.

[0656] Since the conductors 242a and 242b are in contact with the oxide semiconductor 230b, it is preferable to use a conductive material that is not easily oxidized or a conductive material having a function of suppressing oxygen diffusion. Thereby, a decrease in the conductivity of the conductors 242a and 242b can be suppressed. In addition, it is possible to suppress oxygen from being extracted from the oxide semiconductor 230b to form an excessive amount of oxygen vacancies. Further, when a material that easily absorbs (extracts) hydrogen is used as the conductors 242a and 242b, the hydrogen concentration of the oxide semiconductor 230 can be reduced, which is preferable.

[0657] As Figure 48C shown, the conductors 242a and 242b may also have a two-layer structure. The conductor 242a may be a stacked film of a conductor 242a1 and a conductor 242a2 on the conductor 242a1, and the conductor 242b may be a stacked film of a conductor 242b1 and a conductor 242b2 on the conductor 242b1.

[0658] As Figure 48C shown, it is preferable to provide an insulator 255 between the conductor 242a2, the conductor 242b2, the insulator 275, and the insulator 280 and the insulator 250. The insulator 255 is disposed inside the opening formed in the insulator 280 or the like and is in contact with the side surface of the insulator 280, the side surface of the insulator 275, the side surface of the conductor 242a2, the side surface of the conductor 242b2, the top surface of the conductor 242a1, and the top surface of the conductor 242b1. In other words, the insulator 255 is formed so as to be in contact with the side wall of the opening formed in the insulator 280 or the like. That is, the insulator 255 can be referred to as a side wall insulating film.

[0659] The insulator 255 is formed so as to be in contact with the side surfaces of the conductor 242a2 and the conductor 242b2 and is an inorganic insulator that protects the conductor 242a2 and the conductor 242b2. Since it is exposed to an oxidizing atmosphere, the insulator 255 is preferably an inorganic insulator that is not easily oxidized. In addition, the insulator 255 is preferably an inorganic insulator that does not easily oxidize the conductor 242a2 and the conductor 242b2 because it is in contact with the conductor 242a2 and the conductor 242b2.

[0660] By using such an insulator 255, even when heat treatment is performed in an oxygen-containing atmosphere after the conductors 242a1 and 242b1 are separated and before the insulator 250 is deposited, the conductors 242a2 and 242b2 can be prevented from being over-oxidized.

[0661] Note that Figure 48CA structure is shown in which the upper end of the insulator 255 coincides with the top surface of the insulator 280, the upper end of the insulator 250, and the upper end of the conductor 260. However, this embodiment is not limited thereto. The insulator 255 may have a structure that covers the side surfaces of the conductor 242a2 and the conductor 242b2. For example, a structure in which the upper end of the insulator 255 is lower than the top surface of the insulator 280 and higher than the top surface of the insulator 275 may also be employed.

[0662] As Figure 48C shown, in the cross-section in the channel length direction of the transistor 200, the distance (first distance) between the conductor 242a1 and the conductor 242b1 is smaller than the distance (second distance) between the conductor 242a2 and the conductor 242b2. Specifically, the difference between the first distance and the second distance coincides with twice the thickness of the insulator 255. In other words, the first distance coincides with the second distance plus twice the thickness of the insulator 255. Here, the thickness of the insulator 255 refers to the thickness in the A1 - A2 direction of at least a part of the insulator 255. By adopting such a structure, the distance between the source and the drain can be further reduced, and correspondingly, the channel length can be reduced. Therefore, the frequency characteristics of the transistor 200 can be improved. Thus, by realizing miniaturization of the semiconductor device, a semiconductor device with an increased operating speed can be provided.

[0663] Both the conductor 240a and the conductor 240b are provided inside the openings of the insulators 275, 280, 282, and 283. The bottom surface of the conductor 240a is in contact with the top surface of the conductor 242a, and the bottom surface of the conductor 240b is in contact with the top surface of the conductor 242b. Here, the height of the top surface of the conductor 240a and the height of the top surface of the conductor 240b are substantially the same as the height of the top surface of the insulator 283.

[0664] The conductor 240a and the conductor 240b preferably use a conductive material mainly composed of tungsten, copper, or aluminum. In addition, the conductor 240a may have a stacked structure in which the first conductor is disposed in contact with the side surface of the insulator 241a and the second conductor is disposed inside thereof. At this time, the above-mentioned conductive material can be used as the second conductor. Moreover, the same applies to the conductor 240b.

[0665] In addition, when the stacked structure is adopted for the conductor 240a, a conductive material having a function of suppressing the permeation of impurities such as water and hydrogen is preferably used as the first conductor disposed near the insulators 283, 282, 280, and 275. For example, tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, ruthenium oxide, etc. are preferably used. In addition, a single layer or a stack of conductive materials having a function of suppressing the permeation of impurities such as water and hydrogen can also be used. By adopting such a structure, the mixing of impurities such as water and hydrogen in the layer above the insulator 283 into the oxide semiconductor 230 through the conductor 240a can be suppressed. In addition, the same applies to the conductor 240b.

[0666] Both the insulators 241a and 241b are formed in such a manner as to be in contact with the inner walls of the openings of the insulators 275, 280, 282, and 283. The inner side surface of the insulator 241a is in contact with the conduc...

Claims

1. A semiconductor device, comprising: a first insulator; an oxide semiconductor on the first insulator; a first conductor and a second conductor on the oxide semiconductor; a second insulator on the first insulator, the first conductor, and the second conductor; a third insulator on the oxide semiconductor; and a third conductor on the third insulator, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region located between the first region and the second region, the second insulator has an opening in a region overlapping with the third region, at least a part of each of the third insulator and the third conductor is disposed inside the opening, both the first region and the second region are in contact with the first insulator and the second insulator, the third region is in contact with the first insulator and the third insulator, both the first insulator and the second insulator contain silicon and nitrogen, and the first insulator has a region with a thickness of 1.0 nm or more and 5.0 nm or less.

2. A semiconductor device, comprising: a first insulator; an oxide semiconductor on the first insulator; a first conductor and a second conductor on the oxide semiconductor; a second insulator on the first insulator, the first conductor, and the second conductor; a third insulator on the oxide semiconductor; a third conductor on the third insulator; and a fourth insulator on the third insulator and the third conductor, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region located between the first region and the second region, the second insulator has an opening in a region overlapping with the third region, at least a part of each of the third insulator and the third conductor is disposed inside the opening, both the first region and the second region are in contact with the first insulator and the second insulator, the third region is in contact with the first insulator and the third insulator, the first insulator, the second insulator, and the fourth insulator all contain silicon and nitrogen, the first insulator has a region with a thickness smaller than that of the fourth insulator, and the concentration of the impurity element in the first insulator is higher than the concentration of the impurity element in the fourth insulator.

3. The semiconductor device according to claim 2, wherein the impurity element is fluorine, chlorine, bromine, iodine, hydrogen, or carbon.

4. The semiconductor device according to any one of claims 1 to 3, wherein a fourth conductor is further included below the first insulator, and the fourth conductor has a region overlapping with the third conductor with the first insulator, the oxide semiconductor, and the third insulator therebetween.

5. The semiconductor device according to any one of claims 1 to 3, wherein the first insulator is in a strip shape and is disposed to extend in a direction in which the third conductor extends.

6. The semiconductor device according to any one of claims 1 to 3, wherein the first insulator is island-shaped, side ends of the first insulator coincide with side ends of the oxide semiconductor, and the second insulator is in contact with a side surface of the first insulator.

7. The semiconductor device according to any one of claims 1 to 3, wherein a side surface of the third region of the oxide semiconductor near the third insulator includes crystals, the crystals have a crystal structure in which a plurality of layers are stacked, and layers included in the crystals extend in a direction parallel or substantially parallel to the side surface of the oxide semiconductor.

8. A semiconductor device, comprising: a first insulator; a second insulator on the first insulator; an oxide semiconductor located on the first insulator and covering a top surface and a side surface of the second insulator; a first conductor and a second conductor on the oxide semiconductor; a third insulator on the first insulator, the first conductor, and the second conductor; a fourth insulator on the oxide semiconductor; and a third conductor on the fourth insulator, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region located between the first region and the second region, the third insulator has an opening in a region overlapping with the third region, at least a part of each of the fourth insulator and the third conductor is provided inside the opening, both the first region and the second region are in contact with the first insulator, the second insulator, and the third insulator, the third region is in contact with the first insulator, the second insulator, and the fourth insulator, the first insulator, the second insulator, and the third insulator all contain silicon and nitrogen, and the first insulator has a region with a thickness of 1.0 nm or more and 5.0 nm or less.

9. The semiconductor device according to claim 8, wherein a height of the second insulator is greater than a length of the second insulator in a direction in which the third conductor extends.

10. The semiconductor device according to claim 9, wherein a fifth insulator is further included on the fourth insulator and the third conductor, the first insulator has a region with a thickness smaller than that of the fifth insulator, and a concentration of impurity elements in the first insulator is higher than a concentration of impurity elements in the fifth insulator.

11. The semiconductor device according to claim 10, wherein the impurity element is fluorine, chlorine, bromine, iodine, hydrogen, or carbon.

12. The semiconductor device according to claim 9, wherein a side surface of the third region of the oxide semiconductor near the fourth insulator includes crystals, the crystals have a crystal structure in which a plurality of layers are stacked, and layers included in the crystals extend in a direction parallel or substantially parallel to a surface of the oxide semiconductor.

13. A semiconductor device, comprising: a first insulator; The second insulator, the third insulator on the first insulator, and the fourth insulator between the second insulator and the third insulator; The oxide semiconductor on the second insulator, the third insulator, and the fourth insulator; The first conductor and the second conductor on the oxide semiconductor; The fifth insulator on the first insulator, the first conductor, and the second conductor; The sixth insulator on the oxide semiconductor; And The third conductor on the sixth insulator, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region between the first region and the second region, The fifth insulator has an opening in the region overlapping with the third region, At least a part of each of the sixth insulator and the third conductor is provided inside the opening, The first region is in contact with the second insulator and the fifth insulator, The second region is in contact with the third insulator and the fifth insulator, The third region is in contact with the fourth insulator and the sixth insulator, The second insulator, the third insulator, and the fifth insulator all contain silicon and nitrogen, The thicknesses of the second insulator, the third insulator, and the fourth insulator are the same as each other, and the second insulator has a region with a thickness of 1.0 nm or more and 5.0 nm or less.

14. A semiconductor device, comprising: A first insulator; The second insulator, the third insulator on the first insulator, and the fourth insulator between the second insulator and the third insulator; The oxide semiconductor on the second insulator, the third insulator, and the fourth insulator; The first conductor and the second conductor on the oxide semiconductor; The fifth insulator on the first insulator, the first conductor, and the second conductor; The sixth insulator on the oxide semiconductor; The third conductor on the sixth insulator; And The seventh insulator on the sixth insulator and the third conductor, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region between the first region and the second region, The fifth insulator has an opening in the region overlapping with the third region, At least a part of each of the sixth insulator and the third conductor is provided inside the opening, The first region is in contact with the second insulator and the fifth insulator, The second region is in contact with the third insulator and the fifth insulator, The third region is in contact with the fourth insulator and the sixth insulator, The second insulator, the third insulator, the fifth insulator, and the seventh insulator all contain silicon and nitrogen, The thicknesses of the second insulator, the third insulator, and the fourth insulator are the same as each other, The second insulator has a region with a thickness smaller than that of the seventh insulator, Also, the concentration of the impurity element in the second insulator is higher than that in the seventh insulator.

15. The semiconductor device according to claim 14, wherein the impurity element is fluorine, chlorine, bromine, iodine, hydrogen, or carbon.

16. The semiconductor device according to any one of claims 13 to 15, wherein a fourth conductor is further included below the first insulator, and the fourth conductor has a region overlapping with the third conductor with the first insulator, the fourth insulator, the oxide semiconductor, and the sixth insulator therebetween.

17. The semiconductor device according to any one of claims 13 to 15, wherein the second insulator, the third insulator, and the fourth insulator are each strip-shaped and are provided to extend in the direction in which the third conductor extends.

18. The semiconductor device according to any one of claims 13 to 15, wherein the second insulator, the third insulator, and the fourth insulator are each island-shaped, a side end portion of the second insulator coincides with a side end portion of the oxide semiconductor, a side end portion of the third insulator coincides with a side end portion of the oxide semiconductor, a side end portion of the fourth insulator coincides with a side end portion of the oxide semiconductor, and the fifth insulator is in contact with side surfaces of the second insulator and the third insulator.

19. The semiconductor device according to any one of claims 13 to 15, wherein a side surface of the third region of the oxide semiconductor near the sixth insulator includes crystals, the crystals have a crystal structure in which a plurality of layers are stacked, and the layers included in the crystals extend in a manner parallel or substantially parallel to the side surface of the oxide semiconductor.

20. A semiconductor device, comprising: a first insulator; a second insulator, a third insulator on the first insulator, and a fourth insulator between the second insulator and the third insulator; a fifth insulator on the second insulator, the third insulator, and the fourth insulator; an oxide semiconductor covering a top surface and side surfaces of the fifth insulator on the second insulator, the third insulator, and the fourth insulator; a first conductor and a second conductor on the oxide semiconductor; a sixth insulator on the first insulator, the first conductor, and the second conductor; a seventh insulator on the oxide semiconductor; and a third conductor on the seventh insulator, wherein the oxide semiconductor has a first region overlapping with the first conductor, a second region overlapping with the second conductor, and a third region between the first region and the second region, the sixth insulator has an opening in a region overlapping with the third region, at least a part of each of the seventh insulator and the third conductor is provided inside the opening, the first region is in contact with the second insulator, the fifth insulator, and the sixth insulator, the second region is in contact with the third insulator, the fifth insulator, and the sixth insulator, The third region is in contact with the fourth insulator, the fifth insulator, and the seventh insulator. The second insulator, the third insulator, the fifth insulator, and the seventh insulator all contain silicon and nitrogen. The thicknesses of the second insulator, the third insulator, and the fourth insulator are the same as each other. Moreover, the second insulator has a region with a thickness of 1.0 nm or more and 5.0 nm or less.

21. The semiconductor device according to claim 20, wherein the height of the fifth insulator is greater than the length of the fifth insulator in the direction in which the third conductor extends.

22. The semiconductor device according to claim 21, wherein an eighth insulator is further included on the seventh insulator and the third conductor, the second insulator has a region with a thickness smaller than that of the eighth insulator, and the concentration of the impurity element in the second insulator is higher than that of the impurity element in the eighth insulator.

23. The semiconductor device according to claim 22, wherein the impurity element is fluorine, chlorine, bromine, iodine, hydrogen, or carbon.

24. The semiconductor device according to claim 21, wherein the third region of the oxide semiconductor includes crystals on a side surface near the seventh insulator, the crystals have a crystal structure in which a plurality of layers are stacked, and the layers included in the crystals extend in a manner parallel or substantially parallel to the surface of the oxide semiconductor.

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