Semiconductor equipment

Abstract

To provide a semiconductor device using a transistor which can obtain a high ON-state current even when the transistor is microfabricated.SOLUTION: A semiconductor device includes a transistor which has: a pair of first conductive films on an insulation surface; a semiconductor film on the pair of first conductive films; a pair of second conductive films connected to the pair of first conductive films, respectively; an insulation film on the semiconductor film; and a third conductive film on the insulation film, which is provided at a position overlapping the semiconductor film. An end of the third conductive film above the semiconductor film and a region where the pair of second conductive films are provided are separated from each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a semiconductor device using an insulated-gate field-effect transistor. [Background technology]

[0002] In recent years, high mobility has been obtained from polysilicon and microcrystalline silicon, and amorphous silicon As a new semiconductor material that combines uniform device characteristics obtained by the process, oxide semiconductors Metal oxides, which exhibit semiconductor properties and are called conductors, are attracting attention. It is used in various applications; for example, indium oxide, a well-known metal oxide, is used in liquid It is used as a transparent electrode material in crystal display devices, etc. It is a metal oxide exhibiting semiconductor properties. For example, there are tungsten oxide, tin oxide, indium oxide, zinc oxide, and this A transistor that uses a metal oxide exhibiting such semiconductor properties in the channel formation region is already known. (Patent Documents 1 and 2) [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2007-123861 [Patent Document 2] Japanese Patent Publication No. 2007-96055 [Overview of the project] [Problems that the invention aims to solve]

[0004] By the way, in silicon transistors, the addition of trace amounts of impurities to the semiconductor film Valence electron control is performed. However, in transistors using oxide semiconductors, silicon Unlike transistors using other materials, the technology for valence electron control through impurity addition has not been established. Therefore, in a transistor including an oxide semiconductor, a conductive film that functions as a source electrode or a drain electrode is often employed in a structure where the conductive film is directly connected to a channel formation region of a semiconductor film in many cases . Accordingly, in a transistor including an oxide semiconductor, contact resistance between the semiconductor film and the source electrode or the drain electrode is high, which prevents an increase in on-state current from being achieved .

[0005] Further, in a transistor using silicon, a source region and a drain region are formed by adding impurities to a semiconductor film using a gate electrode or a resist as a mask. Therefore, the channel length can be controlled by adjusting the size of the gate electrode or the resist . On the other hand, in a transistor including an oxide semiconductor, the channel length is controlled by adjusting the distance between the source electrode and the drai n electrode. Therefore, to miniaturize a transistor, it is necessary to reduce the distance between the source electrode and the drain electrode ; depending on the size of the gate electrode, the gate electrode may partially overlap with the source electrode or the drain electrode .

[0006] In the case of a top-gate transistor where a gate electrode is provided over a semiconductor film, the source electrode and the drain electrode are preferably provided below the semiconductor film. However, in order to ensure coverage of the semiconductor film (step coverage) at end portions of the source electrode and the drain electrode , it is necessary to reduce the thickness of the source electrode and the drain electrode; however, reducing the thickness increases the resistance of the source electrode and the drain electrode. Therefore, when step coverage is ensured , it is difficult to increase the on-state current of the transistor.

[0007] Given the technical background described above, the present invention can increase the on-current of a transistor. One of our challenges is to provide semiconductor devices that can perform certain functions. [Means for solving the problem]

[0008] In a semiconductor device according to one aspect of the present invention, a transistor is provided with a pair of first conductive films on an insulating surface. And a pair of semiconductor films on the first conductive films, and a pair connected to each of the first conductive films. A second conductive film, an insulating film on the semiconductor film, and a second conductive film, provided on the insulating film at a position overlapping with the semiconductor film. It has a third conductive film. The pair of first conductive films and the pair of second conductive films are connected to the source electrode. It can function as a drain electrode, and the third conductive film can function as a gate electrode. It is possible.

[0009] In one aspect of the present invention, the direction in which carriers move within the semiconductor film is, i.e., the channel length direction. The distance between the source electrode and the drain electrode is determined by the distance between the pair of first conductive films. Yes, it is possible. Therefore, the distance between the pair of second conductive films becomes longer than the distance between the pair of first conductive films. Thus, the arrangement of the pair of second conductive films can be determined. Therefore, in one aspect of the present invention, The miniaturization of transistors has necessitated shortening the distance between the source and drain electrodes. In short, the distance between the pair of first conductive films should be shortened, and the pair of second conductive films and third conductive films should be half The distance between the pair of second conductive films can be increased so that they do not overlap on the conductive film. Specifically, a pair of second conductive films are placed on the semiconductor film, sandwiching and spaced apart from the third conductive film. An electrical film can be formed. Therefore, even if the transistor is miniaturized, the third conductive film can be formed. Because the electric field applied to the semiconductor film is less obstructed by the pair of second conductive films, high ON-voltage You can obtain a flow.

[0010] Furthermore, in one aspect of the present invention, a pair of first conductive films are present beneath the semiconductor film, and on the semiconductor film A third conductive film exists. Therefore, with the miniaturization of transistors, between the pair of first conductive films As the gap shortens, the third conductive film, which functions as a gate electrode, and the pair of first conductive films overlap. However, the electric field applied from the third conductive film to the semiconductor film is obstructed by the pair of first conductive films. It is difficult to miniaturize. Therefore, even when the transistor is miniaturized, a high on-current can be obtained.

[0011] Furthermore, in order to increase the step coverage of the semiconductor film at the edges of the pair of first conductive films Even if the thickness of the pair of first conductive films is kept small, the pair of first conductive films and the pair of second conductive films By connecting the two conductive films, it is composed of a pair of first conductive films and a pair of second conductive films. The resistance of the source electrode or drain electrode can be kept low.

[0012] Alternatively, in a semiconductor device according to one aspect of the present invention, in addition to the above configuration, a pair of second conductive films are It may be located on a semiconductor film.

[0013] When a pair of second conductive films are located on a semiconductor film, the pair of second conductive films separate from the semiconductor film. Rather than when the pair of first conductive films function as source or drain electrodes, This allows for a large contact area between the pair of second conductive films and the semiconductor film. Even when transistors are miniaturized, they are still composed of a pair of first conductive films and a pair of second conductive films. This allows for minimizing the contact resistance between the source or drain electrode and the semiconductor film. Therefore, a high on-current can be obtained. [Effects of the Invention]

[0014] In one aspect of the present invention, a semiconductor device using a transistor with high on-current is provided by the above configuration. This can be achieved. [Brief explanation of the drawing]

[0015] [Figure 1] A diagram showing the configuration of a transistor in a semiconductor device according to one aspect of the present invention. [Figure 2] A diagram showing the configuration of a transistor in a semiconductor device according to one aspect of the present invention. [Figure 3] A diagram showing the configuration of a transistor in a semiconductor device according to one aspect of the present invention. [Figure 4] A diagram showing the configuration of a transistor in a semiconductor device according to one aspect of the present invention. [Figure 5] A diagram showing the configuration of a transistor in a semiconductor device according to one aspect of the present invention. [Figure 6] A diagram illustrating the method for fabricating a semiconductor device. [Figure 7] A diagram illustrating the method for fabricating a semiconductor device. [Figure 8] A diagram illustrating the method for fabricating a semiconductor device. [Figure 9] A diagram showing the structure of a memory cell. [Figure 10] A diagram showing the configuration of a storage device. [Figure 11] A diagram showing the configuration of an inverter. [Figure 12] A diagram of an electronic device. [Modes for carrying out the invention]

[0016] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is... Not limited to the following description, the present invention may have forms and characteristics that do not depart from the spirit and scope of the invention. Those skilled in the art will readily understand that the details can be modified in various ways. Therefore, the present invention This shall not be interpreted as being limited to the contents of the embodiments described below.

[0017] Furthermore, the present invention relates to integrated circuits, RF tags, semiconductor display devices, and other devices that utilize transistors. This category includes all kinds of semiconductor devices. Note that integrated circuits include microprocessors, image processors, etc. Circuitry, DSP (Digital Signal Processor), Microcontroller LSI (Large Scale Integrated Circuit) including Trolla t), FPGA (Field Programmable Gate Array) and C Programmable logic circuits such as PLDs (Complex PLDs) (PLD: Progr Amplifiable Logic Devices (AMMABLE Logic Devices) fall into this category. Also, semiconductor tables... The display device uses light-emitting elements, such as liquid crystal displays and organic light-emitting elements (OLEDs), in each pixel. Equipped with a light-emitting device, electronic paper, and DMD (Digital Micromirror Display). device), PDP (Plasma Display Panel), FED (Fie Examples include ld Emission Display, which have transistors in their drive circuits. Semiconductor display devices fall into that category.

[0018] (Embodiment 1) Figure 1 illustrates the structure of a transistor in a semiconductor device according to one aspect of the present invention. Figure 1(A ) is an example of a cross-sectional view of the transistor in the channel length direction.

[0019] The transistor shown in Figure 1(A) has a first conductive film 101 and a first conductive film 102 on its insulating surface. and the semiconductor film 103 on the first conductive film 101 and the first conductive film 102, and the first conductive film 101 and The second conductive film 104 and the second conductive film 105 are connected to the first conductive film 102 respectively. , an insulating film 106 on the semiconductor film 103, and a second conductive film 10 on the insulating film 106 Between 4 and the second conductive film 105, a third conductive film is provided at a position overlapping with the semiconductor film 103. It has a film 107.

[0020] The first conductive film 101 and the second conductive film 104, and the first conductive film 102 and the second conductive film 105 are It functions as a source electrode or drain electrode. The third conductive film 107 acts as a gate electrode. It works.

[0021] The semiconductor film 103 does not completely cover the first conductive film 101 and the first conductive film 102, The first conductive film 101 and the first conductive film 102 are partially covered. Of the film 101 and the first conductive film 102, the portion not covered by the semiconductor film 103 is In other words, in a portion different from the portion overlapping with the semiconductor film 103, the first conductive film 101 and The first conductive film 102, the second conductive film 104, and the second conductive film 105 are connected to each other. Yes, they are.

[0022] Furthermore, the first conductive film 101 and the first conductive film 102, and the second conductive film 104 and the second conductive film 10 The connection to 5 is not necessarily between the first conductive film 101 and the second conductive film 104, or between the first conductive film 1 This does not mean that 02 and the second conductive film 105 are in direct contact. For example, An insulating film, such as a native oxide film, having a thickness small enough to ensure a gas connection, is used as the first conductive Between the conductive film 101 and the second conductive film 104, or between the first conductive film 102 and the second conductive film 105 It may be provided there.

[0023] Furthermore, in one aspect of the present invention, the edge 107 of the third conductive film 107 on the semiconductor film 103 The second conductive film 104 and the second conductive film 105 are provided so as to sandwich e and spaced apart from each other. That is, the second conductive film 104 and the second conductive film 105 and the third conductive film 107 are semiconductor They do not overlap on the body membrane 103.

[0024] Furthermore, in the channel length direction, the end portion 104e of the second conductive film 104 and the second conductive film 105 Between the edges 105e, the edge 101e of the first conductive film 101 located beneath the semiconductor film 103, The end portion 102e of the first conductive film 102 is located there. 102e is the edge of the first conductive film 101 that is closest to the channel length. This is the part and the end of the first conductive film 102. Therefore, in the channel length direction, the second conductive film 1 The distance Lsd between the end 104e of 04 and the end 105e of the second conductive film 105 is the distance between the first conductive film 10 The distance Lc between the end 101e of part 1 and the end 102e of the first conductive film 102 is longer than the distance Lc.

[0025] In one aspect of the present invention, a first conductive film 101 and a drain electrode function as a source electrode or drain electrode. A semiconductor film 1 is placed between the first conductive film 102 and the third conductive film 107 which functions as a gate electrode. 03 and insulating film 106 are located there. Therefore, the third conductive film 107 and semiconductor film 103 Unlike the case where the first conductive film 101 and the first conductive film 102 are provided in between, Even if the spacing Lc becomes shorter due to the miniaturization of the sta, the third conductive film 107 does not transfer to the semiconductor film 103. The electric field obtained is less likely to be obstructed by the first conductive film 101 and the first conductive film 102. Therefore, even when the transistor is miniaturized, a high on-current can be obtained.

[0026] Furthermore, at the end 101e of the first conductive film 101 and the end 102e of the first conductive film 102, In order to increase the step coverage of the semiconductor film 103, the first conductive film 101 and the first conductive film Even if the film thickness of 102 is kept small, the first conductive film 101 and the first conductive film 102, and the second By connecting the conductive film 104 and the second conductive film 105, the first conductive film 101 and The source electric field is composed of a first conductive film 102, a second conductive film 104 and a second conductive film 105. The resistance of the electrode or drain electrode can be kept low.

[0027] Next, Figure 1(B) shows a top view of a transistor having the cross-sectional structure shown in Figure 1(A). An example is shown. However, in Figure 1(B), in order to clarify the transistor layout, A top view is shown with the insulating film 106 omitted. Also, in Figure 1(B) along the dashed line A1-A2 The cross-sectional view corresponds to Figure 1(A).

[0028] In the top view shown in Figure 1(B), the semiconductor film 103 has openings 108 and 109. And at the opening 108, the first conductive film 101 and the second conductive film 104 are connected. Furthermore, the first conductive film 102 and the second conductive film 105 are connected at the opening 109. It is.

[0029] Next, Figure 1(C) shows a top view of a transistor having the cross-sectional structure shown in Figure 1(A). Another example is shown. However, in Figure 1(C), the transistor layout is made clearer. The top view with the insulating film 106 omitted is shown below. Also, the dashed line A1-A2 in Figure 1(C) The cross-sectional view shown corresponds to Figure 1(A).

[0030] In the top view shown in Figure 1(C), the semiconductor film 103 is separated into three parts. The space between the semiconductor films 103 corresponds to the openings 108 and 109. In 8, the first conductive film 101 and the second conductive film 104 are connected. Also, the opening 10 In 9, the first conductive film 102 and the second conductive film 105 are connected.

[0031] In the transistor shown in Figure 1, the second conductive film 104 or the second conductive film 105 is the first Having a configuration that is connected only to the upper part of the conductive film 101 or to the upper part of the first conductive film 102. However, in one aspect of the present invention, the second conductive film 104 or the second conductive film 105 is the first The upper and end portions of the conductive film 101, or the upper and end portions of the first conductive film 102, are connected. That's good too.

[0032] Figure 2 illustrates the structure of a transistor in a semiconductor device according to one aspect of the present invention. Figure 2(A Figure 2(A) is an example of a cross-sectional view of the transistor in question. Also, Figure 2(B) is shown in Figure 2(A) This is an example of a top view of a transistor having a cross-sectional structure. However, in Figure 2(B), To clarify the layout of the transistor, a top view is shown with the insulating film 106 omitted. Furthermore, the cross-sectional view along the dashed line B1-B2 in Figure 2(B) corresponds to Figure 2(A).

[0033] The transistor shown in Figure 2 has a first conductive film 101 and a first conductive film 102 on an insulating surface, and 1. Semiconductor film 103 on conductive film 101 and first conductive film 102, and first conductive film 101 and 1 Each of the conductive films 102 is connected to the second conductive film 103, and the second conductive film is located on the semiconductor film 103. Film 104 and second conductive film 105, insulating film 106 on semiconductor film 103, and insulating film 106 The device includes a third conductive film 107 provided at a position overlapping with the semiconductor film 103.

[0034] Furthermore, in the transistor shown in Figure 2, the second conductive film 104 and the second conductive film 105 are the first conductive Not only the upper part of the conductive film 101 or the upper part of the first conductive film 102, but also the edges of the first conductive film 101 , or also connected to the end of the first conductive film 102, the transient shown in Figure 1 The structure is different from that of the first conductive film 101 and the first conductive film 102 on the insulating surface. The area (occupied area) of the region provided is the transistor shown in Figure 1 and the transistor shown in Figure 2 If the same as the st, the transistor shown in Figure 2, with the above configuration, the first conductive film 1 The area of ​​the portion where 01 and the second conductive film 104 are connected, or the area of ​​the first conductive film 102 and the second conductive film The area of ​​the portion where film 105 is connected is made larger than that of the transistor shown in Figure 1. This is possible. Therefore, the contact resistance between the first conductive film 101 and the second conductive film 104, or the first The contact resistance between the conductive film 102 and the second conductive film 105 can be reduced.

[0035] In Figures 1 and 2, the second conductive film 104 and the second conductive film 105 are semiconductor films, respectively. The example shows the case where it is in contact with 103. However, in one aspect of the present invention, the second conductive film 10 4 or the second conductive film 105 may be separated from the semiconductor film 103.

[0036] Figure 3 illustrates the structure of a transistor in a semiconductor device according to one aspect of the present invention. Figure 3(A Figure 3(A) is an example of a cross-sectional view of the transistor in question. Also, Figure 3(B) is shown in Figure 3(A) This is an example of a top view of a transistor having a cross-sectional structure. However, in Figure 3(B), To clarify the layout of the transistor, a top view is shown with the insulating film 106 omitted. Furthermore, the cross-sectional view along the dashed line C1-C2 in Figure 3(B) corresponds to Figure 3(A).

[0037] The transistor shown in Figure 3 has a first conductive film 101 and a first conductive film 102 on an insulating surface, and 1. Semiconductor film 103 on conductive film 101 and first conductive film 102, and first conductive film 101 and 1 Each of the second conductive films is connected to the conductive film 102 and is separated from the semiconductor film 103. The conductive film 104 and the second conductive film 105, the insulating film 106 on the semiconductor film 103, and the insulating film 106 The device also includes a third conductive film 107 positioned in a location overlapping with the semiconductor film 103.

[0038] The transistor shown in Figure 3 has a second conductive film 104 or second conductive film 105, and a semiconductor film 10 In terms of being separated from 3, the transistors shown in Figure 1 and Figure 2 are structured together. The construction is different.

[0039] Furthermore, as shown in Figures 1 and 2, the second conductive film 104 and the second conductive film 105 are, When in contact with the semiconductor film 103, as shown in Figure 3, the second conductive film 104 and the second conductive film When 105 is separated from the semiconductor film 103, it is more effective as a source electrode or drain electrode. A first conductive film 101 and a second conductive film 104 that function together, and a first conductive film 102 and a second conductive film The area in contact with the semiconductor film 103 can be made larger. Even if the transistor is miniaturized, the second conductive film 104 and the second conductive film 105 will each be semiconductor By having a configuration in contact with the body membrane 103, the first conductive film 101 and the second conductive film 104 are semi-conductive. Contact resistance of conductive film 103, or the first conductive film 102 and the second conductive film 105 and semiconductor film 1 By keeping the contact resistance of O3 low, a high on-current can be obtained.

[0040] Furthermore, the transistor of the semiconductor device according to one aspect of the present invention is the first conductive film 101 or the first A fourth conductive film may be present beneath the conductive film 102. Figure 4(A) shows one embodiment of the present invention. An example of a cross-sectional view of a transistor in a semiconductor device is shown.

[0041] The transistor shown in Figure 4(A) is a transistor having the cross-sectional structure shown in Figure 1(A). The structure has a fourth conductive film 110 and a fourth conductive film 111 added to it. Specifically, Figure 4 The transistor shown in (A) has a first conductive film 101 and a first conductive film 102, and a first conductive film 1 01 and the semiconductor film 103 on the first conductive film 102, and the first conductive film 101 and the first conductive film 10 The second conductive film 104 and the second conductive film 105 are connected to 2 respectively, and the semiconductor film 103 The upper first insulating film 106 and, on the first insulating film 106, at a position overlapping with the semiconductor film 103 The transistor also has a third conductive film 107 provided. Below 01 and the first conductive film 102, the first conductive film 101 and the first conductive film 102 are in contact with each other. The fourth conductive film 110 and the fourth conductive film 111 are connected, and the fourth conductive film 110 and the fourth conductive film 11 The layer has a second insulating film 120 provided between 1. The upper surface of the above layer is chemically treated. Chemical Mechanical Polishin (CMP) g) It is desirable to flatten the surface by etching or other means.

[0042] The fourth conductive film 110 and the fourth conductive film 111 are the first conductive film 101 and the first conductive film 102, Together with the second conductive film 104 and the second conductive film 105, the source electrode or drain of the transistor It functions as an electrode. Therefore, by providing the fourth conductive film 110 and the fourth conductive film 111 , a first conductive film 101, a second conductive film 104, which function as a source electrode or a drain electrode. , and the overall resistance of the fourth conductive film 110, the first conductive film 102, the second conductive film 105, and the fourth The overall resistance of the conductive film 111 can be kept low.

[0043] Furthermore, the fourth conductive film 110 or the fourth conductive film 111 and the first conductive film 101 or the first conductive film A semiconductor film may be provided between each of the 102. Figure 4(B) shows one of the present inventions. An example of a cross-sectional view of a transistor in a semiconductor device according to the embodiment is shown.

[0044] The transistor shown in Figure 4(B) consists of a first conductive film 101 and a first conductive film 102, and a fourth conductive film A semiconductor film 112 and a semiconductor film 113 are located between film 110 and the fourth conductive film 111, respectively. In this respect, its structure differs from the transistor shown in Figure 4(A).

[0045] In Figure 4, a fourth conductive film is shown in the lower layer of the transistor having the cross-sectional structure shown in Figure 1(A). Although an example has been given of a configuration in which such a feature is provided, one aspect of the present invention is not limited to this configuration. For example, Figure 2( A fourth conductive film is provided in the lower layer of a transistor having the cross-sectional structure shown in A) or Figure 3(A). You can.

[0046] In the transistors shown in Figures 1 to 4, the first conductive film 101 and the first conductive film 102 However, it overlaps with the third conductive film 107 via the semiconductor film 103 and the insulating film 106. In one aspect of the present invention, the first conductive film 101 and the first conductive film 102, and the third conductive film 107 And, through the semiconductor film 103 and the insulating film 106, it does not overlap with the third conductive film 107. That's good too.

[0047] Figure 5(A) shows the cross-sectional structure of the transistor shown in Figure 1(A) as an example, and the first conductive film 1 The distance Lc between the end 101e of 01 and the end 102e of the first conductive film 102, and in the channel length direction. The relationship between the length Lg of the third conductive film 107 and the interval Lc is shown in Figure 5(A). It is longer than that. And, in the transistor shown in Figure 5(A), the third conductive film 107 is a semiconductor film Lov region 114 overlapping with the first conductive film 101 with 103 and the insulating film 106 in between. Then, the third conductive film 107 sandwiches the semiconductor film 103 and the insulating film 106 between them and the first conductive film 10 It has a Lov region 115 that overlaps with 2.

[0048] By providing Lov region 114 or Lov region 115, the on-current of the transistor can be increased. It is possible to do so.

[0049] Furthermore, Figure 5(B) shows the cross-sectional structure of the transistor shown in Figure 1(A) as an example, and the first transistor The distance Lc between the end 101e of the conductive film 101 and the end 102e of the first conductive film 102, and the channel length The relationship between the length Lg of the third conductive film 107 in the direction is shown. In Figure 5(B), the length Lg is It is shorter than the distance Lc. And the transistor shown in Figure 5(B) has a first conductive film 101 and a first In the area between the conductive films 102, the third conductive film 107 and the first conductive film 101 do not overlap. This region is different from the region where the third conductive film 107 and the first conductive film 101 are provided. It has a Loff region 116, which corresponds to the region. Also, the transistor shown in Figure 5(B) is Between the first conductive film 101 and the first conductive film 102, the third conductive film 107 and the first conductive film Regions where 102 does not overlap, i.e., the provision of the third conductive film 107 and the first conductive film 102. It has a Loff region 117 that corresponds to a region different from the region being described.

[0050] By providing Loff region 116 or Loff region 117, the first conductive film 101 and Since the parasitic capacitance between the first conductive film 102 and the third conductive film 107 is kept small, the transient This can increase the operating speed of the system.

[0051] Furthermore, in a transistor of a semiconductor device according to one aspect of the present invention, the semiconductor film 103 is an oxide Wide-bandgap semiconductors such as semiconductors can be used. When a conductor is used, a dopant is added to the semiconductor film 103 to form a source region or An impurity region that functions as a drain region may be formed. The addition of the dopant is ion Injection can be used. Dopants include, for example, helium, argon, and xenon. Noble gases, as well as Group 15 atoms such as nitrogen, phosphorus, arsenic, and antimony, can be used. For example, if nitrogen is used as a dopant, the concentration of nitrogen atoms in the impurity region is 5 × 10 19 / cm 3 The above 1 x 10 22 / cm 3 The following is preferable:

[0052] Furthermore, the oxide semiconductor contains at least indium (In) or zinc (Zn). It is preferable that it contains In and Zn. As a stabilizer to reduce variations in the electrical characteristics of the converters, in addition to them It is preferable to have gallium (Ga). Also, tin (Sn) as a stabilizer is preferable. It is preferable to have it. Furthermore, it is preferable to have hafnium (Hf) as a stabilizer. It is preferable. Furthermore, it is preferable to have aluminum (Al) as a stabilizer.

[0053] Also, other stabilizers include lanthanides such as lanthanum (La) and cerium ( Ce, praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), hol Mium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lu It may contain one or more types of tecium (Lu).

[0054] For example, oxide semiconductors include indium oxide, tin oxide, zinc oxide, and the oxide of binary metals. These are In-Zn oxides, Sn-Zn oxides, Al-Zn oxides, and Zn-Mg oxides. Oxides, Sn-Mg oxides, In-Mg oxides, In-Ga oxides, ternary metals In-Ga-Zn oxides (also written as IGZO), In-Al-Zn oxides Oxides, In-Sn-Zn oxides, Sn-Ga-Zn oxides, Al-Ga-Zn acids oxides, Sn-Al-Zn oxides, In-Hf-Zn oxides, In-La-Zn oxides Materials, In-Ce-Zn oxides, In-Pr-Zn oxides, In-Nd-Zn oxides In-Sm-Zn oxides, In-Eu-Zn oxides, In-Gd-Zn oxides, In-Tb-Zn oxides, In-Dy-Zn oxides, In-Ho-Zn oxides, I n-Er-Zn oxides, In-Tm-Zn oxides, In-Yb-Zn oxides, In -Lu-Zn ​​oxides, In-Sn-Ga-Zn oxides which are oxides of quaternary metals, I n-Hf-Ga-Zn oxides, In-Al-Ga-Zn oxides, In-Sn-Al- Using Zn-based oxides, In-Sn-Hf-Zn-based oxides, and In-Hf-Al-Zn-based oxides It is possible for it to be present. Furthermore, the oxide semiconductor described above may also contain silicon.

[0055] For example, an In-Ga-Zn oxide is an oxide containing In, Ga, and Zn. This is about taste, and the ratio of In, Ga, and Zn is not important. Also, metal elements other than In, Ga, and Zn are not considered. It may contain. In-Ga-Zn oxides have sufficiently high resistance in the absence of an electric field and are off-electric. Because it can reduce the flow rate sufficiently and also has high mobility, it is used in semiconductor devices. It is suitable as a semiconductor material.

[0056] For example, In:Ga:Zn = 1:1:1 (= 1 / 3:1 / 3:1 / 3) or In:G In-Ga-Zn system oxidation with atomic ratio a:Zn=2:2:1 (=2 / 5:2 / 5:1 / 5) Oxides with a similar composition to the substance can be used. Alternatively, In:Sn:Zn=1: 1:1(=1 / 3:1 / 3:1 / 3), In:Sn:Zn=2:1:3(=1 / 3:1 / 6:1 / 2) or In:Sn:Zn=2:1:5 (=1 / 4:1 / 8:5 / 8) It is advisable to use In-Sn-Zn oxides with a specific ratio or oxides with a similar composition.

[0057] For example, high mobility can be obtained relatively easily with In-Sn-Zn oxides. However, Furthermore, even with In-Ga-Zn oxides, mobility can be increased by reducing the bulk defect density. It is possible to do so.

[0058] Furthermore, impurities such as water or hydrogen, which act as electron donors, are reduced, and acid Purified oxide semiconductors (purified Oxi) are achieved by reducing elemental defects. A de Semiconductor is an i-type (intrinsic semiconductor) or very close to an i-type. Therefore, transistors using the above-mentioned oxide semiconductor have the characteristic of having a remarkably low off-current. It has the following characteristics. Furthermore, the band gap of the oxide semiconductor is 2 eV or more, preferably 2.5 eV. More preferably, the voltage is 3 eV or higher. The concentration of impurities such as water or hydrogen is sufficiently reduced. Furthermore, by reducing oxygen deficiency, a highly purified oxide semiconductor film is used. This allows the transistor's off-current to be reduced.

[0059] Specifically, transistors using highly purified oxide semiconductors as semiconductor films have a low off-current. This can be proven through various experiments. For example, if the channel width is 1 × 10⁻⁶ 6 micrometers Even with a channel length of 10 μm, the voltage between the source electrode and the drain electrode (drain electrode) When the voltage is in the range of 1V to 10V, the off-current is measured by a semiconductor parameter analyzer. Below the limit, i.e., 1 × 10⁻⁶ -13 It is possible to obtain the characteristic of being A or less. In this case, The off-current, which corresponds to the value obtained by dividing the f-current by the transistor's channel width, is 100 Hz / μF. It can be seen that it is less than or equal to m. Also, by connecting the capacitive element and the transistor, the current flows through the capacitive element. A circuit is used to control the charge flowing out from an input or capacitive element using the transistor, and the off-power Current measurements were performed. In these measurements, a highly purified oxide semiconductor film was applied to the transistor. Used in the channel formation region, the transition of the charge amount per unit time of the capacitive element is used to determine the transient. The off-current of the transistor was measured. As a result, the voltage between the source and drain electrodes of the transistor was measured. It was found that an even lower off-current of several tens of yA / μm can be obtained when the voltage is 3V. Therefore, transistors that use a highly purified oxide semiconductor film in the channel formation region are The off-current is significantly lower compared to transistors using crystalline silicon.

[0060] Unless otherwise specified, in this specification, off-current refers to the off-current of an n-channel transistor. In this state, the drain electrode is at a higher potential than the source electrode and gate electrode, When the potential of the gate electrode is 0 or less relative to the potential of the source electrode, the source electrode and This refers to the current flowing between the drain electrodes. Alternatively, in this specification, off-current means p In channel transistors, the drain electrode is lower than the source electrode and gate electrode. In a state where the potential is such that the potential of the gate electrode is 0 or less when the potential of the source electrode is used as a reference. This refers to the current flowing between the source electrode and the drain electrode when the voltage is above.

[0061] For example, oxide semiconductor films include In (indium), Ga (gallium), and Zn ( It can be formed by sputtering using a target containing zinc. When depositing a Zn-based oxide semiconductor film by sputtering, preferably, the atomic ratio is In :Ga:Zn=1:1:1, 4:2:3, 3:1:2, 1:1:2, 2:1:3, or A target of an In-Ga-Zn oxide system, represented by the ratio 3:1:4, is used. To deposit an oxide semiconductor film using an In-Ga-Zn-based oxide target having the following properties. Then, polycrystalline or CAAC (C Axis Aligned Crystal) is formed. It becomes easier to remove. Also, the packing density of targets containing In, Ga, and Zn is 90% or more. The fill percentage is 0% or less, preferably 95% or more and less than 100%. A target with a high fill percentage is used. As a result, the deposited oxide semiconductor film becomes a dense film.

[0062] Furthermore, when using an In-Zn-based oxide material as the oxide semiconductor, the target used The atomic ratio of the metal elements is In:Zn = 50:1 to 1:2 (converted to a mole ratio of In2 O3:ZnO = 25:1 to 1:4), preferably In:Zn = 20:1 to 1:1 (number of moles) When converted to a ratio, In2O3:ZnO = 10:1 to 1:2), and more preferably In:Zn = 1.5:1~15:1 (Converted to mole ratio: In2O3:ZnO = 3:4~15:2) ) For example, a target used in the formation of an oxide semiconductor film which is an In-Zn oxide. When the atomic ratio is In:Zn:O=X:Y:Z, assume Z>1.5X+Y. By keeping the rate within the above range, it is possible to improve mobility.

[0063] Oxide semiconductor films can be single crystals, polycrystalline (also called polycrystals), or amorphous. To act in a certain manner.

[0064] Preferably, the oxide semiconductor film is CAAC-OS(C Axis Aligned Cr The film is a ystalline oxide semiconductor film.

[0065] CAAC-OS films are neither perfectly single crystals nor perfectly amorphous. This is an oxide semiconductor film having a crystalline-amorphous multiphase structure with crystalline and amorphous parts in the amorphous phase. Yes, it exists. Furthermore, the crystalline portion must be small enough to fit within a cube with sides less than 100 nm long. There are many. Also, transmission electron microscopes (TEM) In the image observed using a microscope, the amorphous region contained in the CAAC-OS film and The boundary with the crystalline portion is not clear. Also, TEM revealed grain boundaries in the CAAC-OS film. Also called inboundary. ) cannot be confirmed. Therefore, the CAAC-OS film has grain boundaries. The resulting decrease in electron mobility is suppressed.

[0066] The crystalline portion contained in the CAAC-OS film has a c-axis that is the normal vector to the surface on which the CAAC-OS film is formed. Aligned in a direction parallel to the normal vector of the plane or surface, and triangular when viewed from a direction perpendicular to the ab plane. Having a shape or hexagonal atomic arrangement, the metal atoms are layered or when viewed from a direction perpendicular to the c-axis. Metal atoms and oxygen atoms are arranged in layers. Furthermore, between different crystalline regions, the a-axis is... The orientation of the b-axis may be different. In this specification, when simply referred to as vertical, 8 The range of 5° to 95° is also included. Furthermore, when simply describing something as parallel, -5 This will include the range of 5° to 5°.

[0067] Furthermore, the distribution of crystalline regions in the CAAC-OS film does not need to be uniform. For example, CAA In the formation process of a C-OS film, when crystal growth is performed from the surface side of the oxide semiconductor film, the shape The proportion of crystalline material may be higher near the surface compared to near the surface of the material. Also, CA By adding impurities to the AC-OS film, the crystalline region in the impurity-added area becomes amorphous. It can also become qualitative.

[0068] The c-axis of the crystalline portion contained in the CAAC-OS film is the normal vector to the surface on which the CAAC-OS film is formed. Because it aligns in a direction parallel to the normal vector of the surface or the material, the shape of the CAAC-OS film (formed Depending on the cross-sectional shape of the surface or face, they may face in different directions. Oh, the direction of the c-axis of the crystalline portion is the normal vector to the surface on which the CAAC-OS film was formed. The direction is parallel to the normal vector of the crystalline or surface. The crystalline portion is formed by deposition, and It is formed by performing crystallization treatments such as heat treatment after film formation.

[0069] Transistors using CAAC-OS film exhibit changes in electrical characteristics due to irradiation with visible light or ultraviolet light. Dynamics can be reduced. Therefore, this transistor is highly reliable.

[0070] CAAC-OS films are used, for example, for polycrystalline oxide semiconductor sputtering targets. The film is deposited using a sputtering method. Ions are directed onto the sputtering target. Upon collision, the crystalline region contained in the sputtering target cleaves from the ab plane, and a -The sputtering particles are exfoliated as flat or pellet-shaped sputtering particles having a surface parallel to the -b surface. In this case, the flat sputtering particles maintain their crystalline state and form a base By reaching the plate, the CAAC-OS film can be deposited.

[0071] Furthermore, it is preferable to apply the following conditions for forming the CAAC-OS film.

[0072] By reducing the inclusion of impurities during film formation, it is possible to suppress the disruption of the crystalline state due to impurities. For example, the concentration of impurities (hydrogen, water, carbon dioxide, and nitrogen, etc.) present in the deposition chamber. It would be good to reduce it. Also, it would be good to reduce the impurity concentration in the film formation gas. Specifically, the dew point is A film-forming gas with a temperature of -80°C or lower, preferably -100°C or lower, is used.

[0073] Furthermore, by increasing the substrate heating temperature during film deposition, the sputtering particles can be prevented from migrating after reaching the substrate. ration occurs. Specifically, the substrate heating temperature is set to 100°C or higher and 740°C or lower, preferably film formation is performed with the temperature set to 200°C or higher and 500°C or lower. By increasing the substrate heating temperature during film formation, when plate-shaped sputtering particles reach the substrate, migration occurs on the substrate, and the flat surface of the sputtering particles adheres to the substrate.

[0074] In addition, it is preferable to reduce plasma damage during film formation by increasing the oxygen proportion in the film formation gas and optimizing power. The oxygen proportion in the film formation gas is 30% by volume or more, preferably 100% by vo lume.

[0075] An example of a sputtering target is an In-Ga-Zn-O compound target, which is described below.

[0076] InO X powder, GaO Y powder and ZnO Z powder are mixed in predetermined mole numbers, and after pressure treatment , heat treatment is performed at a temperature of 1000°C or higher and 1500°C or lower to obtain a polycrystalline In-Ga -Zn-O compound target. Note that X, Y and Z are arbitrary positive numbers. Herein , the predetermined molar ratio is, for example, for InO X powder, GaO Y powder and ZnO Z powder, the ratio is 2 :2:1, 8:4:3, 3:1:1, 1:1:1, 4:2:3 or 3:1:2. Note that the type of powder and the mixing molar ratio may be appropriately changed depending on the sputtering targe t to be produced.

[0077] (Embodiment 2) A semiconductor device according to one aspect of the present invention may have a configuration in which transistors are stacked. In particular, using a transistor having the configuration shown in Figure 4(A), the fourth conductive film 110 and The fourth conductive film 111 is used as the gate electrode, source electrode, or drain electrode of the underlying transistor. By functioning as an electrode, the increase in element area caused by the contact region is suppressed. To achieve miniaturization of semiconductor devices, or to reduce the number of manufacturing steps for transistors. It is possible.

[0078] In this embodiment, a memory device, which is one type of semiconductor device, is used as an example, as shown in Figure 4(A). The present invention provides a configuration in which another transistor is provided in the lower layer of a transistor having a structure. A method for manufacturing a semiconductor device according to one aspect of this invention will be described.

[0079] First, before explaining the manufacturing method, let's describe the structure of the memory cells in the memory device. .

[0080] Figure 9(A) shows the circuit diagram of the memory cell. The memory cell shown in Figure 9(A) is a transistor It has a 201, a transistor 202, and a capacitive element 203. The electrode is connected to the first word line WLa. Also, transistor 202 is connected to the first word line. One of the electrodes, the drain electrode and the other, is connected to the data line DL, and the other is connected to transistor 2. It is connected to the gate electrode of 01. Transistor 201 has source electrode and drain electrode One pole is connected to the data line DL, and the other is connected to a node that is given a predetermined potential. It is connected to the transistor 201. It is connected to the gate electrode of one terminal and the other to the second word line WLb.

[0081] In the memory cell shown in Figure 9(A), transistor 202 is turned on when data is written. The potential of the signal containing the data from the data line DL is transmitted through transistor 202. It is applied to the gate electrode of transistor 201. Then, according to the potential of the above signal, the transistor By controlling the gate capacitance of 201 and the amount of charge stored in the capacitive element 203, the traction control is achieved. Data is written to the inverter 201 and the capacitive element 203.

[0082] Then, when data is being held, transistor 202 is turned off, and transistor 201 The gate capacitance and the charge stored in the capacitive element 203 are retained. When using an oxide semiconductor for the semiconductor film, the off-current of transistor 202 is made extremely small. Therefore, the accumulated charge is less likely to leak, and transistor 202 Compared to using semiconductor materials such as silicon, it allows for data retention over a longer period of time. It is possible.

[0083] When reading data, the potential of the second word line WLb is changed. Capacitive element 203 is present. The potential difference between the pair of electrodes remains maintained by the law of conservation of charge, so the second word line WL The change in potential at b is applied to the gate electrode of transistor 201. Transistor 201 The threshold voltage changes depending on the amount of charge stored in its gate capacitance. Therefore, The potential of the gate electrode of transistor 201 changes, resulting in the following By reading the difference in the amount of charge stored from the magnitude of the drain current, data It can be read.

[0084] Furthermore, transistor 201 may use an oxide semiconductor for its semiconductor film. In other words, transistor 201 has a semiconductor film made of a semiconductor such as silicon or germanium. It is also acceptable for the following to be used. The semiconductor film of all transistors in the memory cell is made of oxide semiconductor By using a body membrane, the process can be simplified. Also, transistor 201 For semiconductor films, for example, polycrystalline or single-crystal silicon, is more suitable than oxide semiconductors. By using semiconductors that provide high mobility, data can be read from memory cells at high speed. It can be done in this way.

[0085] In this embodiment, silicon is used for the semiconductor film of the lower layer transistor 201, and the upper layer Using the example of using an oxide semiconductor for the semiconductor film of vernista 202, we will explain the fabrication of a semiconductor device. The method will be explained. However, the lower layer transistor 201 is, as mentioned above, a silicon In addition to , semiconductor materials such as germanium, silicon germanium, and single-crystal silicon carbide are also used. It is also acceptable to use it. Also, for example, a transistor using silicon is made from a silicon wafer. Which single-crystal semiconductor substrate, silicon thin film fabricated by SOI method, fabricated by vapor phase growth method It can be formed using a silicon thin film or the like. Alternatively, the lower layer transistor 2 01 may also use an oxide semiconductor, similar to the transistor in the upper layer.

[0086] In this embodiment, first, as shown in Figure 6(A), an insulating film 701 is placed on the substrate 700, and A semiconductor film 702 is formed, separated from the crystalline semiconductor substrate.

[0087] There are no major restrictions on the materials that can be used as substrate 700, but at least, the subsequent processing It is necessary that it has sufficient heat resistance to withstand heat treatment. For example, substrate 700 Glass substrates, quartz substrates, semiconductor substrates, and ceramic substrates fabricated by fusion or float methods. A glass substrate can be used if the temperature of the subsequent heat treatment is high. For this purpose, it is best to use materials with a strain point of 730°C or higher.

[0088] Furthermore, in this embodiment, the case in which the semiconductor film 702 is single-crystal silicon is given as an example. The following describes the method for fabricating transistor 201. Note that specific single-crystal semiconductors are not described. Let me briefly explain one example of a method for fabricating film 702. First, a single-crystal semiconductor substrate is used. An ion beam consisting of ions accelerated by an electric field is injected into the bond substrate, and the surface of the bond substrate From a certain depth, a locally weakened, brittle layer is formed in a region where the crystal structure is disrupted. The depth of the region where the embrittlement layer is formed depends on the acceleration energy of the ion beam and the ion beam It can be adjusted by the angle of incidence. Then, the bond substrate and the insulating film 701 are formed. The substrate 700 is bonded together with the insulating film 701 sandwiched between them. After stacking the bond substrate and substrate 700, a portion of the bond substrate and substrate 700 is coated with 1N / cm 2 More than 500N / cm 2 Preferably 11 N / cm 2 More than 20N / cm 2 below Apply a certain amount of pressure. When pressure is applied, the bond substrate and the insulating film 701 will bond at that point. The process begins, and eventually the bonding extends to the entire surface that is in contact. Next, a heat treatment is performed, The volume of microvoids present in the embrittlement layer increases, and the microvoids bond together. As a result, In the embrittlement layer, the single-crystal semiconductor film, which is part of the bond substrate, separates from the bond substrate. The temperature of the heat treatment described above shall not exceed the strain point of the substrate 700. By processing the conductive film into a desired shape by etching or the like, a semiconductor film 702 is formed. It is possible.

[0089] The semiconductor film 702 contains boron, aluminum, gallium, etc., to control the threshold voltage. Impurity elements that impart p-type conductivity, or elements such as phosphorus and arsenic that impart n-type conductivity. Impurity elements may be added. The addition of impurity elements to control the threshold voltage is a paternalistic approach. This can be done on the semiconductor film before patterning, or on the semiconductor film formed after patterning. This may also be done for 02. In addition, the addition of impurity elements to control the threshold voltage is done by Bon. This can be done on the substrate. Alternatively, the addition of impurity elements can be used to roughly adjust the threshold voltage. To do this, the bond substrate was treated, and then patterning was performed to fine-tune the threshold voltage. This is performed on the previous semiconductor film, or on the semiconductor film 702 formed by patterning. You can.

[0090] In this embodiment, an example using a single-crystal semiconductor film is described, but the present invention The configuration is not limited to this. For example, multiple layers formed on the insulating film 701 using vapor phase growth can be formed. Crystalline, microcrystalline, or amorphous semiconductor films may be used, or the above semiconductor films may be bonded by known techniques. Crystallization is also possible. Known crystallization methods include laser crystallization using laser light and catalyst generation. There are crystallization methods that use elements. Alternatively, a combination of a crystallization method using catalytic elements and a laser crystallization method can be used. They can also be used in combination. Furthermore, when using a substrate with excellent heat resistance, such as quartz... Combined, thermal crystallization method using an electric furnace, lamp annealing crystallization method using infrared light, catalytic elements Crystallization methods using [specific method] or crystallization methods using high-temperature annealing at around 950°C may also be used.

[0091] Next, as shown in Figure 6(B), after forming the gate insulating film 703 on the semiconductor film 702, A mask 705 is formed on the gate insulating film 703, and impurity elements that impart conductivity are added to the semiconductor film. By adding it to a portion of 702, an impurity region 704 is formed.

[0092] The gate insulating film 703 is transformed into a semiconductor film 70 by performing high-density plasma treatment, heat treatment, etc. This can be formed by oxidizing or nitriding the surface of 2. High-density plasma treatment is, for example, Noble gases such as He, Ar, Kr, and Xe, and oxygen, nitrogen oxides, ammonia, nitrogen, hydrogen, etc. This is done using a mixed gas. In this case, the plasma is excited by introducing microwaves. This allows for the generation of high-density plasma at low electron temperatures. Oxygen radicals (sometimes including OH radicals) and nitrogen radicals (NH) generated by Zuma By oxidizing or nitriding the surface of the semiconductor film (which may also contain radicals), An insulating film of 1 to 20 nm, preferably 5 to 10 nm, can be formed in contact with the semiconductor film. For example, dilute nitrous oxide (N2O) with Ar 1 to 3 times (flow rate ratio) and apply at 10 Pa to 30 Applying microwave power of 3kW to 5kW at a pressure of Pa to a semiconductor film The surface of 702 is oxidized or nitrided. This treatment results in a thickness of 1 nm to 10 nm (preferably). It forms an insulating film (2nm~6nm). Furthermore, nitrous oxide (N2O) and silane (SiH4) By introducing this system, a microwave (2.45GHz) of 3kW to 5kW is used at a pressure of 10Pa to 30Pa. By applying power, a silicon oxide nitride film is formed by vapor phase growth to create a gate insulating film. By combining solid-phase reactions and vapor-phase growth reactions, the interface state density is low and the dielectric strength is low. It is possible to form an excellent gate insulating film.

[0093] The oxidation or nitridation of semiconductor films by the high-density plasma treatment described above proceeds as a solid-phase reaction, The interface state density between the insulating film 703 and the semiconductor film 702 can be made extremely low. By directly oxidizing or nitriding the semiconductor film 702 using high-density plasma treatment, an insulating film is formed. This can suppress variations in the thickness of the edge film. Also, if the semiconductor film is crystalline, high density By using plasma treatment to oxidize the surface of a semiconductor film through a solid-state reaction, the grain boundaries are formed. This gate suppresses rapid oxidation only in certain areas, resulting in good uniformity and a low interfacial state density. An insulating film can be formed. The insulating film formed by high-density plasma treatment is gate Transistors formed by incorporating part or all of the insulating film have reduced variations in characteristics. It is possible.

[0094] Furthermore, using plasma CVD or sputtering methods, silicon oxide, silicon nitride, and acid Silicon nitride, silicon nitride, hafnium oxide, aluminum oxide or tantalum oxide, yx oxide Thorium, hafnium silicate (HfSi x O y (x>0, y>0), nitrogen is added. Hafnium silicate (HfSi x O y (x>0, y>0), nitrogen added to the halves HfAl x O y A film containing (x>0, y>0), etc., as a single layer, The gate insulating film 703 may be formed by stacking the layers.

[0095] In this specification, an oxidized nitride is defined as a compound in which the oxygen content is higher than the nitrogen content. It is a substance, and nitride oxides have a higher nitrogen content than oxygen in their composition. It means substance.

[0096] The thickness of the gate insulating film 703 is, for example, 1 nm to 100 nm, preferably 10 nm. The wavelength can be reduced to 50 nm or less. In this embodiment, plasma CVD method is used. A single-layer insulating film containing silicon dioxide is used as the gate insulating film 703.

[0097] Next, after removing the mask 705, as shown in Figure 6(C), one of the gate insulating films 703 The part is removed, and an opening 706 is formed in the region overlapping with the impurity region 704 by etching or the like. After this, conductive films 707 and 708 are formed. Conductive film 707 is formed on transistor 2 Functions as the gate electrode of transistor 01, and as the source or drain electrode of transistor 202. Furthermore, the conductive film 708 is the source electrode or drain electrode of the transistor 201, and It functions as either the source or drain electrode of transistor 202.

[0098] The conductive films 707 and 708 are formed so as to cover the opening 706, and then the conductive films are formed. It can be formed by processing (patterning) the conductive film into a predetermined shape. Conductive film 7 08 is in contact with the impurity region 704 at the opening 706. C is used in the formation of the conductive film. VD method, sputtering method, vapor deposition method, spin coating method, etc. can be used. The film is made of tantalum (Ta), tungsten (W), titanium (Ti), and molybdenum (Mo). Using aluminum (Al), copper (Cu), chromium (Cr), niobium (Nb), etc. This can be done. An alloy with the above metal as the main component may be used, or a compound containing the above metal may be used. Alternatively, a semiconductor film may be doped with impurity elements such as phosphorus to impart conductivity. It may also be formed using semiconductors such as crystalline silicon.

[0099] In this embodiment, conductive films 707 and 708 are formed as single-layer conductive films. However, this embodiment is not limited to this configuration. Conductive films 707 and 708 are laminated It may be formed from multiple conductive films.

[0100] As a combination of two conductive films, the first layer is tantalum nitride or tantalum, and the second layer is tantalum Tungsten can be used. In addition to the above examples, tungsten nitride and tungsten, nitride Examples include molybdenum and molybdenum, aluminum and tantalum, and aluminum and titanium. Tungsten and tantalum nitride have high heat resistance, so after forming a two-layer conductive film, At this stage, a heat treatment can be performed for the purpose of thermal activation. Also, the two-layer conductive film One possible combination is silicon doped with an impurity element that imparts n-type conductivity. and nickel silicide, silicon doped with impurity elements that impart n-type conductivity, and Lungsten silicide and the like can also be used.

[0101] In the case of a three-layer structure with three conductive films stacked on top of each other, the layers are molybdenum film, aluminum film and molybdenum A layered film structure is recommended.

[0102] Furthermore, conductive films 707 and 708 contain indium oxide and a mixture of indium tin oxide. Indium oxide zinc oxide mixture, zinc oxide, zinc aluminum oxide, zinc oxide nitride A light-transmitting oxide conductive film such as zinc or zinc gallium oxide can also be used. .

[0103] Furthermore, conductive films 707 and 708 can be selectively produced using a droplet ejection method without the use of a mask. It may be formed. Droplet dispensing is a method of dispensing or ejecting droplets containing a predetermined composition from a pore. This refers to a method of forming a predetermined pattern, and inkjet printing is included in this category. It can be done.

[0104] Furthermore, after the conductive films 707 and 708 are formed, ICP (Inductive) Inductively coupled plasma (H-Plasma) etching method is used to etch Tapping conditions (amount of power applied to the coil-type electrode layer, amount of power applied to the electrode layer on the substrate side) By appropriately adjusting (such as the electrode temperature on the substrate side), the desired tapered shape can be achieved. It can be etched. Also, the tapered shape can be adjusted by the shape of the mask, including the angle. It can be controlled. Furthermore, chlorine, boron chloride, and silicon chloride can also be used as etching gases. Alternatively, chlorine-based gases such as carbon tetrachloride, tetrafluoride, sulfur fluoride, or nitrogen fluoride may be present. Elementary gases or oxygen can be used as appropriate.

[0105] Next, as shown in Figure 6(D), conductive films 707 and 708 are used as a mask to form a single conductive film. By adding impurity elements that impart to the semiconductor film 702, the channels that overlap with the conductive film 707 A channel-forming region 710, a pair of impurity regions 709 sandwiching the channel-forming region 710, and A portion of the pure region 704 is further divided into an impurity region 711, which is formed by the addition of impurity elements to the semiconductor film 7 It is formed at 02.

[0106] In the present embodiment, an impurity element that imparts p-type conductivity (e.g., boron) is added to the semiconductor film 702 and the case where this is performed is described as an example.

[0107] Next, as shown in FIG. 7(A), an insulating film 712 and an insulating film 713 are formed so as to cover the gate insulating film 703, the conductive film 707, and the conductive film 708. Specifically, the insulating film 712 and the insulating film 713 can be formed using an inorganic insulating film such as silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, aluminum nitride, or aluminum nitride oxide. In particular, using a low-k (low dielectric constant) material for the insulating film 712 and the insulating film 713 is preferable because it can sufficiently reduce the capacitance caused by the overlap between various electrodes and wirings Note that a porous insulating film formed using the above materials may be applied to the insulating film 712 and the insulating film 713. A porous insulating film has a lower dielectric constant than a high-density insulating film, so that the parasitic capacitance caused by electrodes and wirings can be further reduced.

[0108] In the present embodiment, the case where silicon nitride oxide is used for the insulating film 712 and silicon oxynitride is used for the insulating film 713 is described as an example. Further, in the present embodiment, the case where the insulating film 712 and the insulating film 713 are formed over the conductive film 707 and the conductive film 708 is exemplified, but in the present invention, only one insulating film layer may be formed over the conductive film 7 07 and the conductive film 708, or a plurality of three or more insulating layers may be formed to be stacked.

[0109] Next, as shown in FIG. 7(B), CMP, etching, or the like is performed on the insulating film 712 and the insulating film 713 to expose the surfaces of the conductive film 707 and the conductive film 708. Note that in order to improve the characteristics of the transistor 202 that is formed later, the insulating film 712 and the insulating film​​ It is preferable to keep the surface of 713 as flat as possible.

[0110] Through the above process, transistor 201 can be formed.

[0111] Next, we will explain the method for fabricating transistor 202. First, as shown in Figure 7(C) Then, conductive films 714 and 715 are formed on conductive film 707 or conductive film 708. The electrolytic film 714 and the conductive film 715 are connected to the source electrode or drain electrode of the transistor 202. It functions in this way.

[0112] Specifically, conductive film 714 and conductive film 715 are conductive film 707 and conductive film 708, and insulating film After forming a conductive film by sputtering or vapor deposition so as to cover 712 and the insulating film 713, It can be formed by processing (patterning) an electrical film into a predetermined shape. The conductive film 714 and the conductive film 715 are later oxidized on the conductive film 714 and the conductive film 715. To ensure good step coverage of the semiconductor film 716, its edges are tapered. It is desirable that it has a certain shape and that its film thickness is small. Specifically, conductive film 714 and conductive film The taper angle at the end of the 715 is 20 degrees or more and 80 degrees or less, more preferably 30 degrees or more. It is desirable that the temperature be 60 degrees or less. Specifically, the conductive film 714 and conductive film 715 The thickness is 10 nm to 300 nm, more preferably 100 nm to 200 nm. It is desirable to do so.

[0113] The conductive films that become conductive film 714 and conductive film 715 are aluminum, chromium, copper, tantalum, Elements selected from titanium, molybdenum, and tungsten, or compounds containing the above elements. Examples include gold or alloy films combining the elements mentioned above. Other examples include aluminum and copper. Chromium, tantalum, titanium, molybdenum, tungsten, etc. are placed on the underside or top side of the metal film. Any configuration of stacked high-melting-point metal films is acceptable. Furthermore, aluminum or copper has heat resistance. To avoid problems such as corrosion, it is best to use it in combination with high-melting-point metal materials. Metal materials include molybdenum, titanium, chromium, tantalum, tungsten, neodymium, Scandium, yttrium, etc., can be used.

[0114] Furthermore, the conductive films that become conductive film 714 and conductive film 715 may be single-layer or multi-layer structures of two or more layers. It may also be called a structure. For example, a single layer structure of an aluminum film containing silicon, on an aluminum film A two-layer structure in which a titanium film is laminated, a titanium film and an aluminum film layered on top of the titanium film. Examples include a three-layer structure in which layers are stacked and then a titanium film is deposited on top. Also, Cu-Mg -Al alloy, Cu-Mg-O mixed oxide, Cu-Ca-O mixed oxide, Cu-Mg-Al -O mixed oxides, Mo-Ti alloys, Ti, and Mo have high adhesion to oxide films. Therefore, below The layers consist of Cu-Mg-Al alloy, Cu-Mg-O mixed oxide, Cu-Ca-O mixed oxide, and C Conductive film composed of u-Mg-Al-O mixed oxide, Mo-Ti alloy, Ti, or Mo A conductive film composed of Cu with low resistance is laminated on the upper layer, and the laminated conductive film is a conductive film By using 714 and conductive film 715, insulating film 712 or insulating film 713 is an oxide film. In this case, the adhesion between insulating film 712 or insulating film 713 and conductive film 714 and conductive film 715 This can increase the resistance and keep the resistance values ​​of conductive film 714 and conductive film 715 low. It is possible.

[0115] Furthermore, the conductive films to be the conductive film 714 and the conductive film 715 may be formed of a conductive metal oxide . Examples of the conductive metal oxide include indium oxide, tin oxide, zinc oxide, indium indium tin oxide mixture, indium zinc oxide mixture, or those obtained by adding silicon or silicon oxide to the above metal oxide materials can be used.

[0116] Next, as shown in FIG. 8(A), an oxide semiconductor film 7 16 is formed on the conductive film 714 and the conductive film 715. The oxide semiconductor film 716 has an opening 717 on the conductive film 714 and has an opening 718 on the conductive film 715. The oxide semiconductor film 716 is an oxide semiconductor film formed on the insulating film 7 12, the insulating film 713, the conductive film 714 and the conductive film 715 can be formed by processing into the above shape.

[0117] The film thickness of the above oxide semiconductor film is 2 nm or more and 200 nm or less, preferably 3 nm or more and 50 n m or less, more preferably 3 nm or more and 20 nm or less. The oxide semiconductor film is formed into a film by a sputtering method using an oxide semiconduc tor as a target. Further, the oxide semiconductor film can be formed in a noble ga s (e.g., argon) atmosphere, an oxygen atmosphere, or a mixed atmosphere of a noble gas (e.g., argon) and oxygen by a sputtering method.

[0118] As described above, the oxide semiconductor film includes indium oxide, tin oxide, zinc oxide, binary metal oxides: In—Zn-based oxide, Sn—Zn-based oxide, Al—Zn-based oxide, Zn —Mg-based oxide, Sn—Mg-based oxide, In—Mg-based oxide, In—Ga-based oxide, ternary system metal oxide: In-Ga-Zn-based oxide (also referred to as IGZO), In-Al -Zn oxides, In-Sn-Zn oxides, Sn-Ga-Zn oxides, Al-Ga- Zn oxides, Sn-Al-Zn oxides, In-Hf-Zn oxides, In-La-Z n-based oxides, In-Ce-Zn-based oxides, In-Pr-Zn-based oxides, In-Nd-Zn-based oxides In-Sm-Zn oxides, In-Eu-Zn oxides, In-Gd-Zn oxides Oxides, In-Tb-Zn oxides, In-Dy-Zn oxides, In-Ho-Zn acids In-Er-Zn oxides, In-Tm-Zn oxides, In-Yb-Zn oxides In-Lu-Zn ​​oxides, In-Sn-Ga-Zn oxides which are oxides of quaternary metals In-Hf-Ga-Zn oxides, In-Al-Ga-Zn oxides, In-Sn -Al-Zn oxides, In-Sn-Hf-Zn oxides, In-Hf-Al-Zn acids A silicon oxide can be used. Furthermore, the oxide semiconductor may contain silicon.

[0119] In this embodiment, a t In-Ga-Zn oxide semiconductor with a film thickness of 30 nm obtained by sputtering using a GET device. A thin conductive film is used as an oxide semiconductor film. For example, the target composition is... Using an oxide target with a molar ratio of In2O3:Ga2O3:ZnO = 1:1:1 It exists. Also, the oxide ter with In2O3:Ga2O3:ZnO = 1:1:2 [molar ratio] Get may be used. Also, the packing density of the target containing In, Ga, and Zn is 90%. The percentage is 100% or less, preferably 95% or more and less than 100%. Targets with a high filling rate. By using this method, the deposited oxide semiconductor film becomes a dense film.

[0120] Furthermore, when using an In-Zn oxide as an oxide semiconductor, the metal in the target used The number of atoms in each element is In:Zn = 50:1 to 1:2 (converted to a mole ratio, In2O3: ZnO = 25:1 to 1:4), preferably In:Zn = 20:1 to 1:1 (molar ratio) When converted, In2O3:ZnO = 10:1 to 1:2), and more preferably In:Zn = 1 5:1 to 1.5:1 (converted to a mole ratio of In2O3:ZnO = 15:2 to 3:4) For example, the target used for forming In-Zn oxide semiconductors has an atomic ratio of I When n:Zn:O=X:Y:Z, assume Z>1.5X+Y.

[0121] Furthermore, the target used for In-Sn-Zn oxides is the atom of the metal element in the target. The numerical ratios are In:Sn:Zn = 1:2:2, 2:1:3, 1:1:1, or 20:45: An oxide target with a value of 35 is used.

[0122] In this embodiment, the substrate is held in a processing chamber that is maintained under reduced pressure, and residual moisture in the processing chamber is removed. Sputtered gas from which hydrogen and water have been removed while removing the above target is introduced, and the above target is used An oxide semiconductor film is formed. During film formation, the substrate temperature is preferably between 100°C and 600°C. The temperature may be between 200°C and 400°C. By depositing the film while heating the substrate, The concentration of impurities in the deposited oxide semiconductor film can be reduced. Damage caused by suction is reduced. To remove residual moisture in the processing chamber, an adsorption-type vacuum port is used. It is preferable to use a pump. For example, a cryopump, ion pump, or titanium sublimation pump. It is preferable to use a pressure pump. In addition, as an exhaust means, a pressure pump is used for the turbo pump. A rud trap may also be added. When the treatment chamber is evacuated using a cryopump... For example, hydrogen atoms, compounds containing hydrogen atoms such as water (H2O) (more preferably carbon atoms) Compounds containing (and others) are exhausted, so the oxide semiconductor film deposited in the processing chamber contains The concentration of impurities can be reduced.

[0123] An example of film deposition conditions is a distance of 100 mm between the substrate and the target, and a pressure of 0.6 Pa. The conditions applied are a DC power supply of 0.5kW and an oxygen atmosphere (oxygen flow rate ratio of 100%). Furthermore, using a pulsed DC power supply can reduce dust generated during film formation, and the film This is preferable because it results in a uniform thickness distribution.

[0124] Furthermore, etching for forming the oxide semiconductor film 716 can be done using dry etching or wet etching. Etching can be done with a dry etching tool, or both can be used. Etching tools used for dry etching Examples include chlorine-containing gases (chlorine-based gases, such as chlorine (Cl2) and boron trichloride (BCl). 3) Silicon tetrachloride (SiCl4), carbon tetrachloride (CCl4), etc. are preferred. Gases containing fluorine (fluorinated gases, such as carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), Nitrogen trifluoride (NF3), trifluoromethane (CHF3), etc., hydrogen bromide (HBr), Oxygen (O2), and noble gases such as helium (He) and argon (Ar) are added to these gases. Gases such as those mentioned above can be used.

[0125] As for dry etching methods, parallel plate type RIE (Reactive Ion Etching) Methods such as the ing method and ICP (Inductively Coupled Plasma: induction) A coupled plasma etching method can be used. It can etch into the desired shape. Etching conditions (amount of power applied to the coil-type electrode, amount of power applied to the electrode on the substrate side) Adjust the power consumption, electrode temperature on the substrate, etc., as appropriate.

[0126] For wet etching, an etching solution made by mixing phosphoric acid, acetic acid, and nitric acid, and quer Organic acids such as oxalic acid and oxalic acid can be used. In this embodiment, ITO-07N Use (manufactured by Kanto Chemical Co., Ltd.).

[0127] Even if a resist mask for forming the oxide semiconductor film 716 is formed by an inkjet method Good. Since a resist mask is formed using an inkjet method, a photomask is not used. Manufacturing costs can be reduced.

[0128] Furthermore, in oxide semiconductor films formed by sputtering, etc., water or hydrogen may be present as impurities. It may contain a large amount of acidic groups. Water or hydrogen readily forms donor levels. Therefore, it is an impurity for oxide semiconductors. In one aspect of the present invention, oxide semiconductors In order to reduce impurities such as moisture or hydrogen in the conductive film (dehydration or dehydrogenation), oxidation For the monocrystalline semiconductor film 716, under a reduced pressure atmosphere, under an inert gas atmosphere such as nitrogen or a rare gas, acid Under a gas atmosphere or in ultra-dry air (CRDS (Cavity Ring-Down Laser Spectroscopy)) When measured using a dew point meter of a certain type, the moisture content is 20 ppm or less (equivalent to a dew point of -55°C). Preferably in an air atmosphere of 1 ppm or less, preferably 10 ppb or less, oxide semiconductor The film 716 is subjected to heat treatment.

[0129] By subjecting the oxide semiconductor film 716 to heat treatment, moisture or hydrogen in the oxide semiconductor film 716 is released. It can be detached. Specifically, 250°C to 750°C, preferably 400°C The heat treatment should be performed at a temperature above 500°C but below the strain point of the substrate. For example, 500°C for 3 minutes or more. It should be done in about 6 minutes or less. If the RTA method is used for heat treatment, dehydration or dehydration can be achieved in a short time. Because it can perform materialization, processing can be done even at temperatures exceeding the strain point of the glass substrate.

[0130] In this embodiment, an electric furnace is used as one of the heat treatment devices. Not limited to furnaces, heat conduction or thermal radiation from heat-generating elements such as resistance heating elements can be used to process materials. It may be equipped with a heating device. For example, GRTA (Gas Rapid Therm al Anneal) equipment, LRTA (Lamp Rapid Thermal Anneal) equipment, LRTA (Lamp Rapid Thermal Anneal) equipment, Using RTA (Rapid Thermal Anneal) devices such as eal devices This is possible. The LRTA device uses halogen lamps, metal halide lamps, and xenon arc lamps. Lamps such as carbon arc lamps, high-pressure sodium lamps, and high-pressure mercury lamps It is a device that heats the object to be processed by radiating light (electromagnetic waves) emitted from it. The GRTA device is This is a device that performs heat treatment using high-temperature gas. The gas can be a noble gas such as argon, or An inert gas, such as nitrogen, that does not react with the material being treated during heat treatment is used.

[0131] In the heat treatment, nitrogen, or a noble gas such as helium, neon, or argon is used, along with water or water It is preferable that it does not contain elements such as nitrogen or helium. Alternatively, nitrogen or helium introduced into the heat treatment device. The purity of noble gases such as neon and argon is 6N (99.9999%) or higher, preferably 7 N(99.99999%) or higher (i.e., impurity concentration of 1 ppm or less, preferably 0.1 ppm), It is preferable to use a value of 0.5 (pm or less).

[0132] Furthermore, oxide semiconductors are insensitive to impurities, and the film contains a considerable amount of metallic impurities. It is safe to use, and inexpensive sodalite contains a large amount of alkali metals such as sodium. It has also been pointed out that ash glass can be used (Kamiya, Nomura, Hosono, "Amorphous oxide semiconductors "Current Status of Materials Properties and Device Development," Solid State Physics, September 2009, Vol. 44, pp. 62. 1-633.). However, such a statement is inappropriate. Alkali metals form oxide semiconductors. Since it is not a constituent element, it is an impurity. Alkaline earth metals also constitute oxide semiconductors. When it is not an element, it becomes an impurity. In particular, among alkali metals, Na is an oxide. When the insulating film in contact with the semiconductor film is an oxide, Na diffuses into the insulating film. + This is how it will be. Furthermore, Na breaks the bonds between the metal and oxygen that constitute the oxide semiconductor within the oxide semiconductor film. It interrupts or interrupts the connection. As a result, for example, the threshold voltage moves in the negative direction. Degradation of transistor characteristics, such as normalization and decreased mobility due to shifting. This occurs, and in addition, variations in characteristics also occur. This impurity causes transistors The degradation of properties and the variation in properties occur when the hydrogen concentration in the oxide semiconductor film is sufficiently low. This becomes particularly noticeable. Therefore, when the hydrogen concentration in the oxide semiconductor film is 1 × 10⁻⁶ 18 / cm 3 below, Especially 1x10 17 / cm 3 In the following cases, it is desirable to reduce the concentration of the above impurities. Specifically, the measured Na concentration by secondary ion mass spectrometry is 5 × 10⁻⁶. 16 / cm 3 The following is preferably 1 × 1016 / cm 3 More preferably, 1 × 10 15 / cm 3 Below It is best to do it as shown below. Similarly, the measured value of Li concentration is 5 × 10 15 / cm 3 The following, preferably 1 x 10 15 / cm 3 The following is recommended. Similarly, the measured value of the K concentration is 5 × 10 15 / c m 3 The following is preferably 1 × 10 15 / cm 3 The following is recommended.

[0133] Through the above process, the hydrogen concentration in the oxide semiconductor film 716 is reduced, and its purity is increased. Yes, it is possible. This allows for the stabilization of oxide semiconductor films. Also, the glass transition temperature The following heat treatment results in an oxide semiconductor film with extremely low carrier density and a wide band gap. This allows for the formation of transistors using large-area substrates. This allows for increased mass production efficiency. Furthermore, the hydrogen concentration is reduced and the oxidation is purified. By using a monocrystalline semiconductor film, transistors with high breakdown voltage and extremely low off-current can be fabricated. It is possible.

[0134] Furthermore, the oxide semiconductor film may be amorphous, but it may also be crystalline. The oxide semiconductor film having c-axis orientation is a crystal (CAAC: C Axis Al Even oxide semiconductors containing igned crystals can improve transistor reliability. It is desirable because it can be used to enhance the effect.

[0135] Oxide semiconductor films composed of CAAC can also be fabricated by sputtering. It is possible. To obtain CAAC by sputtering, the initial stage of oxide semiconductor film deposition is The goal is to create a hexagonal crystal and to grow a crystal using that crystal as a seed. It is essential to do so. To achieve this, the distance between the target and the substrate should be increased (for example (For example, 150mm to 200mm), the substrate heating temperature should be 100℃ to 500℃, preferably 20 A temperature of 0°C to 400°C is preferable, and more preferably 250°C to 300°C. Furthermore, the deposited oxide semiconductor film is heat-treated at a temperature higher than the substrate heating temperature during film formation. This allows for the repair of microscopic defects contained within the film and defects at the layered interface.

[0136] CAAC-OS(C Axis Aligned Crystalline Oxide Semiconductors, compared to amorphous oxide semiconductors, have a bond between metal and oxygen. The mixture is ordered. That is, in the case of an amorphous oxide semiconductor, the individual metal atoms are ordered. Although the coordination number may differ, in CAAC-OS the coordination number of metal atoms is almost constant. Therefore, microscopic oxygen deficiencies are reduced, and hydrogen atoms (including hydrogen ions) and alkalis are produced. It has the effect of reducing the release of metal atoms, the transfer of charge due to bonding, and instability.

[0137] Therefore, transistors are fabricated using an oxide semiconductor film composed of CAAC-OS. Therefore, after applying light irradiation or bias-thermal stress (BT) to the transistor... The resulting change in the transistor's threshold voltage can be reduced. Therefore, stability Transistors with the specified electrical characteristics can be fabricated.

[0138] Next, as shown in Figure 8(B), the conductive film 714 and the oxide semiconductor film 716 are in contact with each other. A film 719 and a conductive film 720 that is in contact with the conductive film 715 and the oxide semiconductor film 716 are formed. The conductive film 719 and conductive film 720 are made of the same material as conductive film 714 and conductive film 715, similar to the conductive film 714 and conductive film 715. The laminated structure can be formed using a similar manufacturing method.

[0139] Furthermore, in etching when forming conductive film 719 and conductive film 720, oxide semiconductor To minimize the removal of film 716, the materials and etching conditions were adjusted as appropriate. Depending on the etching conditions, the exposed portion of the oxide semiconductor film 716 may be partially etched. This process can sometimes create grooves (recesses).

[0140] In this embodiment, titanium films are used for conductive films 719 and 720. Therefore, Using a solution containing Monia and hydrogen peroxide (ammonia peroxide), the conductive film 719 and The conductive film 720 can be wet-etched. Specifically, 31% by weight of peroxide Hydrogenated water, 28% by weight ammonia water, and water are mixed in a volume ratio of 5:2:2. Use peroxide. Alternatively, use a gas containing chlorine (Cl2), boron chloride (BCl3), etc. Alternatively, the conductive film can be dry-etched.

[0141] Furthermore, the oxide semiconductor film 716 and the conductive film 71 which functions as a source electrode or drain electrode Between 9 and the conductive film 720, zinc oxide, zinc aluminum oxide, zinc oxide aluminum A conductive metal oxide film, such as gallium oxide or zinc oxide, may also be provided. For example, when forming a metal oxide film, patterning is required to form the metal oxide film, The patterning for forming the conductive film 719 and the conductive film 720 is performed in a single operation. This is also good. By providing the above metal oxide film, the oxide semiconductor film 716 and the conductive film 719 and the conductive This reduces the resistance between the film 720, enabling high-speed operation of the transistor. This can be done. Furthermore, by providing a metal oxide film, the breakdown voltage of the transistor can be increased. can.

[0142] Next, plasma treatment may be performed using a gas such as N2O, N2, or Ar. This plasma treatment removes water and other substances adhering to the surface of the exposed oxide semiconductor film. Remove. Alternatively, plasma treatment may be performed using a mixed gas of oxygen and argon.

[0143] Furthermore, after plasma treatment, conductive film 719 and conductive film 72 are as shown in Figure 8(C). A gate insulating film 721 is formed so as to cover 0 and the oxide semiconductor film 716. Then, A conductive film 722 is formed on the gate insulating film 721 at a position overlapping with the oxide semiconductor film 716. Then, a conductive film 723 is formed in a position that overlaps with the conductive film 719. The conductive film 722 is transient It functions as the gate electrode of STA202.

[0144] The gate insulating film 721 is formed using the same material and layered structure as the gate insulating film 703. It is possible to do so. Furthermore, the gate insulating film 721 is designed to minimize the amount of impurities such as water and hydrogen. It is preferable that it not contain any insulating film, and it may be a single layer insulating film or a stack of multiple insulating films. It may be done. If hydrogen is included in the gate insulating film 721, that hydrogen will be in the oxide semiconductor. Hydrogen penetrates into the film 716, or extracts oxygen from the oxide semiconductor film 716, causing the oxide semiconductor The membrane 716 may become less resistive (n-type), potentially leading to the formation of parasitic channels. Therefore, the gate insulating film 721 is designed to be a film that contains as little hydrogen as possible, and the film deposition method is designed to avoid hydrogen It is important not to use [this]. The gate insulating film 721 above should be made of a material with high barrier properties. It is desirable to do so. For example, as insulating films with high barrier properties, silicon nitride film, silicon oxide nitride film, Aluminum nitride film or aluminum nitride oxide film can be used. Multiple layers When using layered insulating films, silicon oxide films, silicon oxide nitride films, etc., which have a low nitrogen content. The insulating film is formed closer to the oxide semiconductor film 716 than the insulating film with high barrier properties. Then, an insulating film with a low nitrogen content is sandwiched in between, and conductive film 719 and conductive film 720 and A highly barrier insulating film is formed so as to overlap with the oxide semiconductor film 716. By using a high insulating film, within the oxide semiconductor film 716, within the gate insulating film 721, or, Impurities such as water or hydrogen enter the interface between the oxide semiconductor film 716 and the other insulating film, and in its vicinity. This prevents it from being incorporated. Also, the ratio of nitrogen is such that it is in contact with the oxide semiconductor film 716. By forming insulating films such as low silicon oxide films and silicon oxidnitride films, high barrier properties can be achieved. This prevents the insulating film used from directly contacting the oxide semiconductor film 716.

[0145] In this embodiment, on a silicon oxide film with a thickness of 200 nm formed by sputtering, A gate insulating film 7 has a structure in which silicon nitride films with a thickness of 100 nm formed by the method are stacked. Form 21. The substrate temperature during film formation should be between room temperature and 300°C, and the form of this embodiment The temperature is set to 100°C.

[0146] Furthermore, a heat treatment may be performed after the gate insulating film 721 is formed. The heat treatment may be performed using nitrogen. Preferably, in an atmosphere of ultra-dry air or a noble gas (argon, helium, etc.). The process is carried out at a temperature between 200°C and 400°C, for example, between 250°C and 350°C. The gas mentioned above is water. The content is 20 ppm or less, preferably 1 ppm or less, more preferably 10 ppb or less. It is desirable to do so. In this embodiment, for example, heating at 250°C for 1 hour under a nitrogen atmosphere. Perform the process. Alternatively, before forming conductive films 719 and 720, reduce moisture or hydrogen. Similar to the heat treatment previously performed on the oxide semiconductor film to reduce its density, high temperature and short duration RT Treatment A may be performed. After the gate insulating film 721 containing oxygen is provided, heat treatment is performed. As a result of the heat treatment performed on the oxide semiconductor film 716, Even if oxygen vacancies occur in the semiconductor film 716, the oxide semiconductor can still be transmitted from the gate insulating film 721. Oxygen is donated to the body membrane 716. And oxygen is donated to the oxide semiconductor film 716. Therefore, in the oxide semiconductor film 716, the oxygen vacancies that serve as donors are reduced, and the stoichiometric composition is It is possible to satisfy this condition. The oxide semiconductor film 716 contains an amount of oxygen exceeding the stoichiometric composition. It is preferable that it contains. As a result, the oxide semiconductor film 716 is brought closer to type i. This reduces variations in the electrical characteristics of transistors due to oxygen deficiency, and improves the electrical characteristics. The above can be achieved. The timing of this heat treatment depends on the shape of the gate insulating film 721. There are no particular limitations as long as it is after the formation process, such as heat treatment during resin film formation or transparent conductive film By combining this with a heat treatment to reduce resistance, the oxide semiconductor can be processed without increasing the number of steps. The body membrane 716 can be made closer to type i.

[0147] Furthermore, by heat-treating the oxide semiconductor film 716 under an oxygen atmosphere, the oxide semiconductor is subjected to acid By adding an element, the oxygen vacancies that act as donors in the oxide semiconductor film 716 may be reduced. The heat treatment temperature is, for example, 100°C or more and less than 350°C, preferably 150°C or more and 250°C. The process should be carried out at temperatures below °C. The oxygen gas used in the above-mentioned heat treatment under an oxygen atmosphere may contain water, hydrogen, etc. It is preferable that it is not included. Alternatively, the purity of the oxygen gas introduced into the heat treatment device should be 6N (9 9.9999% or more, preferably 7N (99.99999%) or more (i.e., ions in oxygen) It is preferable to have a pure substance concentration of 1 ppm or less, preferably 0.1 ppm or less.

[0148] Alternatively, an acid may be injected into the oxide semiconductor film 716 using an ion implantation method or an ion doping method. By adding an element, the oxygen deficiency in the donor can be reduced. For example, 2.45 GH The solution is to add oxygen, which has been plasma-generated using z-wave microwaves, to the oxide semiconductor film 716.

[0149] Furthermore, the conductive films 722 and 723 are formed on the gate insulating film 721 after the conductive films have been formed on the gate insulating film 721. The conductive film can be formed by patterning. Conductive film 722 and conductive film 72 3 is a material similar to conductive film 707 and conductive film 708, or conductive film 714 and conductive film 715. It can be formed using materials.

[0150] The thickness of conductive film 722 and conductive film 723 is 10 nm to 400 nm, preferably 100 nm. The wavelength is set to ~200 nm. In this embodiment, a sputtering method using a tungsten target is used. After forming a conductive film for a gate electrode with a diameter of 150 nm, the conductive film is etched to the desired extent. Conductive films 722 and 723 are formed by processing (patterning) them into the specified shape. The resist mask may also be formed by an inkjet method. Since the wet process does not require the use of a photomask, manufacturing costs can be reduced.

[0151] Through the above process, transistor 202 is formed.

[0152] Furthermore, the portion where the conductive film 719 and the conductive film 723 overlap with the gate insulating film 721 in between, This corresponds to capacitive element 203.

[0153] Furthermore, although transistor 202 was explained using a single-gate transistor, it is not necessary to... Depending on the requirements, the channel formation region is formed by having multiple electrically connected gate electrodes. It is also possible to form transistors with multiple gates, creating a multi-gate structure.

[0154] Furthermore, the insulating film in contact with the oxide semiconductor film 716 (in this embodiment, the gate insulating film 7 21 is applicable.) Insulating materials containing Group 13 elements and oxygen may be used. Many oxide semiconductor materials contain Group 13 elements, and insulating materials containing Group 13 elements are It has good compatibility with oxide semiconductors, and by using it as an insulating film in contact with an oxide semiconductor film, acid The interface with the ionized semiconductor film can be kept in good condition.

[0155] An insulating material containing a Group 13 element means that the insulating material contains one or more Group 13 elements. It tastes good. Examples of insulating materials containing Group 13 elements include gallium oxide and aluminum oxide. Examples include aluminum oxide, gallium oxide, and aluminum gallium oxide. Here, aluminum oxide Luminium gallium is defined as having a higher aluminum content (atomic %) than gallium content (atomic %). This indicates a high percentage of gallium, and gallium aluminum oxide is a product of the gallium content (atomic %). This indicates a content of aluminum (atomic %) or higher.

[0156] Furthermore, the insulating film in contact with the oxide semiconductor film 716 can be subjected to heat treatment in an oxygen atmosphere or oxygen atmosphere. It is preferable to make the insulating material have a higher oxygen content than its stoichiometric composition by means of a pneumatic agent. Plasma doping may be performed using ion implantation or ion doping methods.

[0157] By performing oxygen doping, an insulating film having a region with more oxygen than the stoichiometric composition is obtained. It can be formed. When an insulating film having such a region comes into contact with an oxide semiconductor film Therefore, excess oxygen in the insulating film is supplied to the oxide semiconductor film, and in the oxide semiconductor film, or oxidation Reduce oxygen vacancies at the interface between the semiconductor film and the insulating film, and convert the oxide semiconductor film to type i or type i It can be made to come as close as possible.

[0158] Furthermore, Figure 9(B) shows another circuit of a memory cell in a semiconductor device according to one aspect of the present invention. The diagram is shown.

[0159] The memory cell shown in Figure 9(B) has a transistor 204 and a capacitive element 205. The gate electrode of transistor 204 is connected to the word line WL. In 204, one of the source and drain electrodes is connected to the data line DL, and the other is It is connected to one electrode of the capacitive element 205. The other electrode of the capacitive element 205 is connected to the ground. It is connected to a node to which a fixed potential, such as a position, is provided.

[0160] In the memory cell shown in Figure 9(B), transistor 204 is turned on when data is written. The potential of the signal containing the data from the data line DL is transmitted through transistor 204 to the capacitive element. It is applied to one electrode of 205. Then, according to the potential of the above signal, the capacitive element 205 By controlling the amount of accumulated charge, data is written to the capacitive element 205. It can be done.

[0161] Next, when data is being held, transistor 204 is turned off, and capacitive element 205 is... The charge is retained. Transistor 204 has the characteristic of having an extremely small off-current. Therefore, the charge stored in the capacitive element 205 is less likely to leak, and the transistor 20 Compared to using semiconductor materials such as silicon in step 4, data can be retained for a longer period of time. It is possible.

[0162] When data is read, transistor 204 turns on, and capacitance is transmitted via the data line DL. The charge accumulated in element 205 is extracted. Then, the difference in the amount of charge is read. This allows the data to be read.

[0163] Figure 10(A) shows an example of a cross-sectional view of the memory cell shown in Figure 9(B). Transistor 20 4 is a conductive film 751 and a conductive film 752 on a substrate 750 having an insulating surface, and conductive film 751 and connected to the semiconductor film 753 on the conductive film 752, and to the conductive film 751 and conductive film 752, respectively. The conductive films 754 and 755, the insulating film 756 on the semiconductor film 753, and the insulating film The film 756 has a conductive film 757 provided at a position overlapping with the semiconductor film 753. .

[0164] Furthermore, the capacitive element 205 has a conductive film 755 on a substrate 750 having an insulating surface, and a conductive film 75 The insulating film 756 on 5, and the conductive film 755 formed on the insulating film 756 at a position overlapping with the conductive film 755 It has a conductive film 758.

[0165] Furthermore, in one aspect of the present invention, a semiconductor device is provided with a lower layer of memory cells that controls the driving of the memory cells. A drive circuit may be provided to control it. Figure 10(B) shows the memory cell and the drive circuit integrated. An example of a cross-sectional view of a layered storage device is shown.

[0166] In the memory device shown in Figure 10(B), the transistor 206 that constitutes the drive circuit is located on the insulating surface A semiconductor film 761 and an insulating film 762 on the semiconductor film 761 are provided on a substrate 760 having the above characteristics. A conductive film 763 is provided on film 762 at a position overlapping with the semiconductor film 761, and the semiconductor film It has conductive films 764 and 765 connected to 761. 761, insulating film 762, and conductive film 763 are covered by insulating film 766, and insulating film 762 , and through the openings provided in the insulating film 766, the semiconductor film 761 and the conductive film 764 It is connected to the film 765.

[0167] Furthermore, transistor 204 has a conductive film 780 on the conductive film 764 and insulating film 766, and a conductive film 760. It has a film 781 and an insulating film 782 provided between the conductive film 780 and the conductive film 781. The film 764 is connected to the conductive film 781. Furthermore, the transistor 204 is connected to the conductive film 7 On a layer composed of 80, a conductive film 781, and an insulating film 782, the conductive film 780 and the conductive film 782 Conductive films 771 and 772 are connected to the conductive film 781, respectively, and conductive film 771 and The semiconductor film 773 on the electrode film 772 is connected to the conductive film 771 and the conductive film 772, respectively. Conductive films 774 and 775, and semiconductor film 773, conductive film 774 and conductive film 775 The upper insulating film 776 and the semiconductor film 773 are provided on the insulating film 776 at a position that overlaps with the semiconductor film 773. It has a conductive film 777 and

[0168] The capacitive element 205 consists of a conductive film 775, an insulating film 776 on the conductive film 775, and on the insulating film 776 The device has a conductive film 783 located on the conductive film 775.

[0169] This embodiment can be implemented in appropriate combination with the above embodiment.

[0170] (Embodiment 3) An example of the configuration of an inverter, which is one of the semiconductor devices according to one aspect of the present invention, will be described.

[0171] Figure 11 shows an example of an inverter according to one aspect of the present invention. The inverter 50 shown in Figure 11 0 has transistors 501 to 505 and a capacitive element 506.

[0172] Transistor 501 has its gate electrode connected to wiring 508, and its source electrode is connected to the transistor It is connected to the drain electrode of the inverter 502, and that drain electrode is connected to the wiring 507. Transistor 502 has its gate electrode connected to wiring 509, and its source electrode It is connected to wiring 510, and its drain electrode is connected to the source electrode of transistor 501. Transistor 503 has its gate electrode connected to wiring 507, and its source One of the electrodes and the drain electrode is the source electrode of transistor 501 and the other is the source electrode of transistor 502 It is connected to the drain electrode, and the other end is connected to the gate electrode of transistor 504. Transistor 504 has its source electrode connected to the drain electrode of transistor 505. It is connected to wire 511, and its drain electrode is connected to wire 507. Transistor 5 05 has its gate electrode connected to wiring 509 and its source electrode connected to wiring 510. The drain electrode is connected to the source electrode and wiring 511 of transistor 504. ru.

[0173] The capacitive element 506 has one electrode connected to the gate electrode of the transistor 504, and The other electrode is connected to wiring 511.

[0174] If transistors 502 and 505 are of the n-channel type, specifically, the wiring A high-level potential VDD is applied to wire 507, and a low-level potential VSS is applied to wire 510. The potential CL of the clock signal is given to wiring 508, and wiring 509 is given A potential Vin is applied. Then, from wiring 511, the polarity of the potential Vin is reversed. The resulting potential Vinb is output.

[0175] In a semiconductor device according to one aspect of the present invention, even if the transistor is miniaturized, the source electrode or By keeping the resistance of the conductive film that functions as the drain electrode low, a high on-current can be ensured. Therefore, by applying the configuration of the present invention to the inverter 500, the inverter 500 Even with miniaturization, it is possible to ensure high operating speed and increase current supply capacity.

[0176] This embodiment can be implemented in appropriate combination with other embodiments.

[0177] (Embodiment 4) A semiconductor device according to one aspect of the present invention comprises a display device, a personal computer, and a recording medium. Image playback devices (typically DVDs: Digital Versatile Discs) To be used in a device that has a display capable of playing back recording media such as the above and displaying the images thereof. This is possible. In addition, electronic devices that can use a semiconductor device according to one aspect of the present invention And mobile phones, game consoles including portable devices, personal digital assistants, e-books, video cameras, digital cameras Still camera, goggle-type display (head-mounted display), navigation Sound systems, audio playback devices (car audio, digital audio players, etc.), Photocopiers, fax machines, printers, multifunction printers, automated teller machines (AT) Examples include vending machines. Specific examples of these electronic devices are shown in Figure 12.

[0178] Figure 12(A) shows a portable game console, comprising a casing 5001, casing 5002, display unit 5003, Display unit 5004, microphone 5005, speaker 5006, operation keys 5007, stand It includes illustration 5008, etc. A semiconductor according to one aspect of the present invention is used in the drive circuit of a portable game console. By using this device, it is possible to provide a portable game console with high operating speed. Alternatively, By using a semiconductor device according to one aspect of the present invention, it is possible to miniaturize a portable game console. This is possible. Note that the portable game console shown in Figure 12(A) has two display units 5003 and Although it has a display unit 5004, the number of display units that a portable game console has is not limited to this. do not have.

[0179] Figure 12(B) shows a display device, which includes a housing 5201, a display unit 5202, a support base 5203, etc. To do so, by using a semiconductor device according to one aspect of the present invention in the drive circuit of a display device, the operating speed A display device with high speed can be provided. Alternatively, a semiconductor device according to one aspect of the present invention can be provided. By using this, it is possible to miniaturize the display device. Note that the display device uses a personal computer. This includes all information display devices, such as those for computer systems, TV broadcast reception, and advertising displays. Born.

[0180] Figure 12(C) shows a notebook personal computer, consisting of a casing 5401 and a display unit 5402. It has a keyboard 5403, a pointing device 5404, etc. Notebook personal By using a semiconductor device according to one aspect of the present invention in the drive circuit of a computer, the operating speed It is possible to provide a fast notebook personal computer. Alternatively, one of the present inventions By using the semiconductor device described in this embodiment, miniaturization of notebook personal computers can be achieved. It is possible.

[0181] Figure 12(D) shows a portable information terminal, consisting of a first housing 5601, a second housing 5602, and a first display unit. It includes 5603, a second display unit 5604, a connection unit 5605, an operation key 5606, etc. Table 1 The display unit 5603 is provided in the first housing 5601, and the second display unit 5604 is provided in the second housing 56 It is located at 02. And the first housing 5601 and the second housing 5602 are connected at the connection part 56 They are connected by 05, and the angle between the first housing 5601 and the second housing 5602 is the connection part This can be changed by 5605. The video switching in the first display unit 5603 is connected Switching according to the angle between the first housing 5601 and the second housing 5602 in section 5605 It is also acceptable to have a configuration that allows for this. Also, at least the first display unit 5603 and the second display unit 5604 Alternatively, a semiconductor display device with added functionality as a position input device may be used. Furthermore, the function as a position input device is achieved by providing a touch panel on the semiconductor display device. It can be added. Alternatively, its function as a position input device is also called a photosensor. This can also be added by providing the photoelectric conversion element in the pixel portion of a semiconductor display device. By using a semiconductor device according to one aspect of the present invention in the drive circuit of a mobile information terminal, the operating speed can be increased. It is possible to provide a fast mobile information terminal. Alternatively, a semiconductor device according to one aspect of the present invention By using this technology, it becomes possible to miniaturize mobile information terminals.

[0182] Figure 12(E) is a mobile phone, comprising a housing 5801, a display unit 5802, an audio input unit 5803, It has an audio output unit 5804, an operation key 5805, a light receiving unit 5806, etc. By converting the received light into an electrical signal, external images can be captured. By using a semiconductor device according to one aspect of the present invention in the drive circuit of a mobile phone, a high operating speed can be achieved. A mobile phone can be provided. Alternatively, a semiconductor device according to one aspect of the present invention can be used. This makes it possible to miniaturize mobile phones.

[0183] This embodiment can be implemented in appropriate combination with other embodiments. [Explanation of Symbols]

[0184] 101 Conductive film 101e End 102 Conductive film 102e end 103 Semiconductor film 104 Conductive film 104e end 105 Conductive film 105e end 106 Insulating film 107 Conductive film 107e End 108 Opening 109 Opening 110 Conductive film 111 Conductive film 112 Semiconductor film 113 Semiconductor film 114 Lov area 115 Lov area 116 Loff area 117 Loff area 120 insulating film 201 Transistors 202 transistors 203 Capacitive element 204 transistors 205 Capacitive element 206 transistors 500 Inverter 501 Transistors 502 Transistors 503 Transistors 504 Transistors 505 transistors 506 Capacitive element 507 Wiring 508 Wiring 509 Wiring 510 Wiring 511 Wiring 700 circuit boards 701 Insulating Film 702 Semiconductor film 703 Gate Insulator 704 Impurity region 705 Mask 706 Opening 707 Conductive film 708 Conductive film 709 Impurity region 710 Channel formation region 711 Impurity region 712 Insulating film 713 Insulating film 714 Conductive film 715 Conductive film 716 oxide semiconductor film 717 Opening 718 Opening 719 Conductive film 720 Conductive film 721 Gate insulating film 722 Conductive film 723 Conductive film 750 circuit boards 751 Conductive film 752 Conductive film 753 Semiconductor film 754 Conductive film 755 Conductive film 756 Insulating film 757 Conductive film 758 Conductive film 760 circuit boards 761 Semiconductor film 762 Insulating film 763 Conductive film 764 Conductive film 765 Conductive film 766 Insulating film 771 Conductive film 772 Conductive film 773 Semiconductor film 774 Conductive film 775 Conductive film 776 insulating film 777 Conductive film 780 Conductive film 781 Conductive film 782 Insulating film 783 Conductive film 5001 enclosure 5002 enclosure 5003 Display section 5004 Display section 5005 Microphone 5006 Speaker 5007 Operation Keys 5008 Stylus 5201 enclosure 5202 Display section 5203 Support stand 5401 enclosure 5402 Display section 5403 Keyboard 5404 Pointing device 5601 enclosure 5602 enclosure 5603 Display section 5604 Display section 5605 Connection part 5606 Operation Keys 5801 enclosure 5802 Display section 5803 Voice Input Section 5804 Audio output section 5805 Operation Keys 5806 Light receiving section

Claims

1. A circuit comprises a first transistor, a second transistor, and a capacitive element. The source electrode or drain electrode of the first transistor is electrically connected to the gate electrode of the second transistor. One of the source electrode or drain electrode of the first transistor is electrically connected to one electrode of the capacitive element. The other electrode of the capacitive element is a semiconductor device to which a signal is input, A first conductive film having an overlap with the channel formation region of the second transistor, A second conductive film, An oxide semiconductor film disposed on the upper layer of the first conductive film and the upper layer of the second conductive film, and having a channel formation region for the first transistor, A third conductive film is disposed on top of the oxide semiconductor film, electrically connected to the first conductive film, and functions as either the source electrode or the drain electrode of the first transistor. A fourth conductive film is disposed on top of the oxide semiconductor film, electrically connected to the second conductive film, and functions as the other of the source electrode or drain electrode of the first transistor. The film comprises a fifth conductive film disposed on top of the oxide semiconductor film and functioning as the gate electrode of the first transistor, The third conductive film functions as one electrode of the capacitive element. The third conductive film has a region in contact with the upper surface of the oxide semiconductor film, The fourth conductive film has a region in contact with the upper surface of the oxide semiconductor film, In a plan view, the fifth conductive film is separated from the third conductive film and the fourth conductive film. Semiconductor equipment.

2. A circuit comprises a first transistor, a second transistor, and a capacitive element. The source electrode or drain electrode of the first transistor is electrically connected to the gate electrode of the second transistor. One of the source electrode or drain electrode of the first transistor is electrically connected to one electrode of the capacitive element. The other electrode of the capacitive element is a semiconductor device to which a signal is input, A first conductive film having an overlap with the channel formation region of the second transistor, A second conductive film, An oxide semiconductor film disposed on the upper layer of the first conductive film and the upper layer of the second conductive film, and having a channel formation region for the first transistor, A third conductive film is disposed on the upper layer of the oxide semiconductor film, has a region in contact with the first conductive film, and functions as either the source electrode or the drain electrode of the first transistor. A fourth conductive film is disposed on the upper layer of the oxide semiconductor film, has a region in contact with the second conductive film, and functions as the other of the source electrode or drain electrode of the first transistor. The film comprises a fifth conductive film disposed on top of the oxide semiconductor film and functioning as the gate electrode of the first transistor, The third conductive film functions as one electrode of the capacitive element. The third conductive film has a region in contact with the upper surface of the oxide semiconductor film, The fourth conductive film has a region in contact with the upper surface of the oxide semiconductor film, In a plan view, the fifth conductive film is separated from the third conductive film and the fourth conductive film. Semiconductor equipment.

3. A circuit comprises a first transistor, a second transistor, and a capacitive element. The source electrode or drain electrode of the first transistor is electrically connected to the gate electrode of the second transistor. A first potential is applied to either the source electrode or the drain electrode of the second transistor. One of the source electrode or drain electrode of the first transistor is electrically connected to one electrode of the capacitive element. The other electrode of the capacitive element is a semiconductor device to which a signal is input, A first conductive film having an overlap with the channel formation region of the second transistor, A second conductive film, An oxide semiconductor film disposed on the upper layer of the first conductive film and the upper layer of the second conductive film, and having a channel formation region for the first transistor, A third conductive film is disposed on top of the oxide semiconductor film, electrically connected to the first conductive film, and functions as either the source electrode or the drain electrode of the first transistor. A fourth conductive film is disposed on top of the oxide semiconductor film, electrically connected to the second conductive film, and functions as the other of the source electrode or drain electrode of the first transistor. The film comprises a fifth conductive film disposed on top of the oxide semiconductor film and functioning as the gate electrode of the first transistor, The third conductive film functions as one electrode of the capacitive element. The third conductive film has a region in contact with the upper surface of the oxide semiconductor film, The fourth conductive film has a region in contact with the upper surface of the oxide semiconductor film, In a plan view, the fifth conductive film is separated from the third conductive film and the fourth conductive film. Semiconductor equipment.

4. A circuit comprises a first transistor, a second transistor, and a capacitive element. The source electrode or drain electrode of the first transistor is electrically connected to the gate electrode of the second transistor. A first potential is applied to either the source electrode or the drain electrode of the second transistor. One of the source electrode or drain electrode of the first transistor is electrically connected to one electrode of the capacitive element. The other electrode of the capacitive element is a semiconductor device to which a signal is input, A first conductive film having an overlap with the channel formation region of the second transistor, A second conductive film, An oxide semiconductor film disposed on the upper layer of the first conductive film and the upper layer of the second conductive film, and having a channel formation region for the first transistor, A third conductive film is disposed on the upper layer of the oxide semiconductor film, has a region in contact with the first conductive film, and functions as either the source electrode or the drain electrode of the first transistor. A fourth conductive film is disposed on the upper layer of the oxide semiconductor film, has a region in contact with the second conductive film, and functions as the other of the source electrode or drain electrode of the first transistor. The film comprises a fifth conductive film disposed on top of the oxide semiconductor film and functioning as the gate electrode of the first transistor, The third conductive film functions as one electrode of the capacitive element. The third conductive film has a region in contact with the upper surface of the oxide semiconductor film, The fourth conductive film has a region in contact with the upper surface of the oxide semiconductor film, In a plan view, the fifth conductive film is separated from the third conductive film and the fourth conductive film. Semiconductor equipment.

5. In any one of claims 1 to 4, The oxide semiconductor film contains indium oxide, Semiconductor equipment.

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