Semiconductor device

Abstract

Provided is a semiconductor device capable of changing a storage region of each level of a storage device. A semiconductor device includes a storage device having first and second storage circuits and a control circuit. The first storage circuit includes a first capacitor and a first transistor having a function of holding the charge held by the first capacitor. The second storage circuit includes a second transistor, a second capacitor electrically connected to a gate of the second transistor, and a third transistor having a function of holding the charge held by the second capacitor. The first and third transistors include a semiconductor layer having an oxide semiconductor, a gate, and a back gate. Each storage region in the first or second storage circuit is changed by adjusting a voltage applied to the back gate of the first or third transistor.

Description

Technical Field

[0001] One aspect of the present invention relates to a semiconductor device.

[0002] Note that one aspect of the present invention is not limited to the above technical field. One aspect of the invention disclosed in this specification etc. relates to an object, a method, or a manufacturing method. Additionally, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Additionally, one aspect of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a storage device, a driving method thereof, or a manufacturing method thereof. Background Art

[0003] For computer systems that perform data processing, various structures are proposed according to the use. In many computer systems, the following architecture is adopted, that is, the memory unit is divided into multiple levels and storage devices with different performances are allocated to each level. As such a computer structure, a structure having storage devices such as registers, cache memories, main storage devices, and auxiliary storage devices is widely known.

[0004] Patent Document 1 discloses an invention in which a storage circuit using a transistor including an oxide semiconductor in a semiconductor layer is applied to a register, a cache memory, and a main storage device. Since the oxide semiconductor has a wider bandgap than silicon etc. and its intrinsic carrier concentration is small, a transistor including an oxide semiconductor in the semiconductor layer has a characteristic of extremely small off-state current. Thus, by using this transistor for a storage circuit, the stored data can be held for a long time.

[0005] [Prior Art Documents]

[0006] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-180994 Summary of the Invention

[0008] Technical Problem to be Solved by the Invention

[0009] The performances required for a register, a cache memory, and a main storage device are different from each other. Therefore, it is difficult for them to share a storage area. Specifically, for example, when the storage capacity of the cache memory is insufficient, it is difficult to use the main storage device to make up for the shortage.

[0010] One of the objectives of one embodiment of the present invention is to provide a novel semiconductor device. Another objective of one embodiment of the present invention is to provide a semiconductor device capable of reducing power consumption. Another objective of one embodiment of the present invention is to provide a semiconductor device capable of reducing the area. Another objective of one embodiment of the present invention is to provide a semiconductor device capable of achieving a large capacity of a storage device.

[0011] Note that one embodiment of the present invention does not need to achieve all of the above objectives, as long as at least one objective can be achieved. In addition, the description of the above objectives does not prevent the existence of other objectives. Other objectives than the above can be obviously seen and extracted from the descriptions in the specification, drawings, claims, etc.

[0012] Means for Solving Technical Problems (1)

[0014] One embodiment of the present invention is a semiconductor device including: a storage device; and a control circuit. The storage device includes a first storage circuit operating at a first storage hierarchy and a second storage circuit operating at a second storage hierarchy. The access speed of the first storage hierarchy is faster than that of the second storage hierarchy. The first storage circuit includes a first capacitor and a first transistor having a function of holding the charge held by the first capacitor. The second storage circuit includes a second transistor, a second capacitor electrically connected to the gate of the second transistor, and a third transistor having a function of holding the charge held by the second capacitor. The first and third transistors include a semiconductor layer having an oxide semiconductor, a first gate, and a second gate. The control circuit has a function of changing the first storage circuit from the first storage hierarchy to the second storage hierarchy by inputting a voltage to the second gate of the first transistor and a function of changing the second storage circuit from the second storage hierarchy to the first storage hierarchy by inputting a voltage to the second gate of the third transistor. (2)

[0016] In addition, in the structure of the above (1), one embodiment of the present invention is a semiconductor device, wherein the control circuit includes a temperature detection circuit. The temperature detection circuit has a function of outputting a correction voltage corresponding to the temperature near the storage device, and the control circuit has a function of fluctuating the voltage applied to the second gate of each of the first and third transistors according to the correction voltage. (3)

[0018] In addition, one aspect of the present invention is a semiconductor device including: a storage device; and a control circuit. The storage device includes a first storage circuit operating at a first storage level and a second storage circuit operating at a second storage level. The access speed of the first storage level is faster than that of the second storage level. The first storage circuit includes a first capacitor and a first transistor having a function of holding the charge held by the first capacitor. The second storage circuit includes a second transistor, a second capacitor electrically connected to the gate of the second transistor, and a third transistor having a function of holding the charge held by the second capacitor. The first and third transistors include a semiconductor layer having an oxide semiconductor, a first gate, and a second gate. The control circuit has a function of changing the first storage circuit from the first storage level to the second storage level by inputting a voltage to the second gate of the first transistor and a function of changing the second storage circuit from the second storage level to the first storage level by inputting a voltage to the second gate of the third transistor. The control circuit includes a controller, a plurality of voltage generation circuits, and a switching circuit. The storage device has a function of outputting a signal indicating the usage status of the storage capacity of the storage device to the controller. Further, the controller has a function of controlling the switching circuit so that a voltage output from any one of the plurality of voltage generation circuits is applied to the second gates of the first and third transistors based on the signal. (4)

[0020] In addition, in the structure of (3) above, one aspect of the present invention is a semiconductor device, wherein the control circuit includes a temperature detection circuit. The temperature detection circuit has a function of outputting a correction voltage corresponding to the temperature near the storage device, and the control circuit has a function of fluctuating the voltage applied to the second gate of each of the first and third transistors based on the correction voltage. (5)

[0022] In addition, one aspect of the present invention is a semiconductor device including: a storage device; and a control circuit. The storage device includes a first storage circuit operating at a first storage level and a second storage circuit operating at a second storage level. The access speed of the first storage level is faster than that of the second storage level. The first storage circuit includes a first capacitor and a first transistor having a function of holding the charge held by the first capacitor. The second storage circuit includes a second transistor, a second capacitor electrically connected to the gate of the second transistor, and a third transistor having a function of holding the charge held by the second capacitor. The first and third transistors include a semiconductor layer having an oxide semiconductor, a first gate, and a second gate. The control circuit has a function of changing the first storage circuit from the first storage level to the second storage level by inputting a voltage to the second gate of the first transistor and a function of changing the second storage circuit from the second storage level to the first storage level by inputting a voltage to the second gate of the third transistor. The control circuit includes a controller, a plurality of voltage generation circuits, and a switching circuit. The storage device has a function of outputting a signal indicating the usage of the storage capacity of the storage device to the controller. The controller has a function of controlling the switching circuit such that a voltage output from any one of the plurality of voltage generation circuits is applied to the second gates of the first and third transistors based on the signal. Further, the first storage circuit includes a region overlapping with the second storage circuit. (6)

[0024] In addition, in the structure of (5) above, one aspect of the present invention is a semiconductor device, wherein the control circuit includes a temperature detection circuit having a function of outputting a correction voltage corresponding to the temperature near the storage device, and the control circuit has a function of fluctuating the voltage applied to the second gate of each of the first and third transistors based on the correction voltage. (7)

[0026] In addition, in any one of the structures of (1) to (6) above, one aspect of the present invention is a semiconductor device, wherein the oxide semiconductor contains one or more materials selected from indium, element M (element M is aluminum, gallium, yttrium, or tin), and zinc.

[0027] Note that in this specification and the like, a semiconductor device refers to a device utilizing semiconductor characteristics, a circuit including semiconductor elements (transistors, diodes, photodiodes, etc.), and a device including such a circuit. In addition, a semiconductor device refers to all devices that can function by utilizing semiconductor characteristics. For example, as examples of semiconductor devices, there are integrated circuits, chips having integrated circuits, and electronic components in which chips are housed in packages. In addition, a storage device, a display device, a light-emitting device, a lighting device, and an electronic device, etc. are themselves semiconductor devices or sometimes include semiconductor devices.

[0028] In addition, in this specification and the like, when it is described that "X is connected to Y", it means that the following cases are disclosed in this specification and the like: the case where X is electrically connected to Y; the case where X is functionally connected to Y; and the case where X is directly connected to Y. Therefore, it is not limited to the connection relationship shown in the drawings or the text. For example, other connection relationships are also described within the scope described in the drawings or the text. Both X and Y are objects (for example, devices, components, circuits, wirings, electrodes, terminals, conductive films, layers, etc.).

[0029] As an example of the case where X and Y are electrically connected, one or more components capable of electrically connecting X and Y (such as switches, transistors, capacitors, inductors, resistors, diodes, display elements, light-emitting elements, loads, etc.) can be connected between X and Y. In addition, the switch has a function of controlling on or off. In other words, whether to allow current to flow is controlled by making the switch in a conductive state (on state) or a non-conductive state (off state).

[0030] As an example of the case where X and Y are functionally connected, for example, one or more circuits capable of functionally connecting X and Y (such as logic circuits (inverters, NAND circuits, NOR circuits, etc.), signal conversion circuits (DA circuits, AD conversion circuits, gamma correction circuits, etc.), potential level conversion circuits (power supply circuits (boost circuits, buck circuits, etc.), level shift circuits that change the potential level of a signal, etc.), voltage sources, current sources, switching circuits, amplifier circuits (circuits capable of increasing the signal amplitude or current amount, operational amplifiers, differential amplifier circuits, source follower circuits, buffer circuits, etc.), signal generation circuits, storage circuits, control circuits, etc.) can be connected between X and Y. Note that, for example, even if there are other circuits between X and Y, when the signal output from X is transmitted to Y, it can be said that X and Y are functionally connected.

[0031] In addition, when it is explicitly described that "X is electrically connected to Y", it includes the following cases: the case where X is electrically connected to Y (in other words, the case where X and Y are connected with other components or other circuits in between); the case where X is functionally connected to Y (in other words, the case where X and Y are functionally connected with other circuits in between); and the case where X is directly connected to Y (in other words, the case where X and Y are connected without other components or other circuits in between). In other words, when "electrically connected" is explicitly described, it is the same as the case where only "connected" is explicitly described.

[0032] For example, it can be expressed as "X, the source (or the first terminal, etc.) of the transistor, and the drain (or the second terminal, etc.) of the transistor are electrically connected to each other, and X, the source (or the first terminal, etc.) of the transistor, the drain (or the second terminal, etc.) of the transistor, and Y are electrically connected in sequence". Or, it can be expressed as "the source (or the first terminal, etc.) of the transistor is electrically connected to X, the drain (or the second terminal, etc.) of the transistor is electrically connected to Y, and X, the source (or the first terminal, etc.) of the transistor, the drain (or the second terminal, etc.) of the transistor, and Y are electrically connected in sequence". Or, it can be expressed as "X is electrically connected to Y through the source (or the first terminal, etc.) and the drain (or the second terminal, etc.) of the transistor, and X, the source (or the first terminal, etc.) of the transistor, the drain (or the second terminal, etc.) of the transistor, and Y are arranged in sequence". By using the same display method as this example to stipulate the connection order in the circuit structure, the source (or the first terminal, etc.) and the drain (or the second terminal, etc.) of the transistor can be distinguished to determine the technical scope. Note that this display method is an example and is not limited to the above display method. Here, X, Y, Z1, and Z2 are objects (for example, devices, components, circuits, wirings, electrodes, terminals, conductive films, layers, etc.).

[0033] In addition, even when the independent components on the circuit diagram are electrically connected to each other, sometimes one component has the functions of multiple components. For example, when a part of the wiring is used as an electrode, one conductive film has the functions of two components, namely the wiring and the electrode. Therefore, the scope of "electrically connected" in this specification also includes the case where one conductive film has the functions of multiple components.

[0034] In this specification and the like, a transistor includes three terminals: a gate, a source, and a drain. The gate is used as a control terminal for controlling the on-state of the transistor. The two terminals used as the source or the drain are the input / output terminals of the transistor. Depending on the conductivity type of the transistor (n-channel type, p-channel type) and the levels of the potentials applied to the three terminals of the transistor, one of the two input / output terminals is used as the source and the other is used as the drain. Therefore, in this specification and the like, the source and the drain can be interchanged. In this specification and the like, when explaining the connection relationship of the transistor, the expressions "one of the source and the drain" (the first electrode or the first terminal) and "the other of the source and the drain" (the second electrode or the second terminal) are used. In addition, depending on the structure of the transistor, sometimes in addition to the above three terminals, it also includes a back gate.

[0035] In addition, in this specification and the like, a node can also be referred to as a terminal, a wiring, an electrode, a conductive layer, a conductor, or an impurity region, etc. according to the circuit structure or the device structure, etc. In addition, a terminal, a wiring, etc. can also be referred to as a node.

[0036] In addition, in this specification and the like, "voltage" and "electric potential" can be appropriately interchanged. "Voltage" refers to the potential difference from a reference potential. For example, when the reference potential is the ground potential (earthing potential), "voltage" can also be referred to as "electric potential". The ground potential does not necessarily mean 0V. Note that electric potential is relative, and the potential supplied to wirings and the like sometimes changes according to the reference potential.

[0037] "Current" is generally defined as the movement phenomenon of charge (electric conduction) accompanying the movement of positively charged bodies. For example, the description "positive charged body conduction occurs" can be replaced with the description "negative charged body conduction occurs in the opposite direction". Therefore, in this specification and the like, without special explanation, "current" refers to the movement phenomenon of charge (electric conduction) when carriers move. Here, examples of carriers include electrons, holes, anions, cations, complex ions, etc., and carriers vary depending on the system through which the current flows (for example, semiconductors, metals, electrolytes, in a vacuum, etc.). In addition, the "direction of current" in wirings and the like is the direction of positive carrier movement, and is recorded as a positive current amount. In other words, the direction of negative carrier movement is opposite to the current direction and is recorded as a negative current amount. Therefore, in this specification and the like, without special explanation, regarding the positive and negative of current (or the direction of current), descriptions such as "current flows from element A to element B" can be replaced with descriptions such as "current flows from element B to element A". In addition, descriptions such as "input current to element A" can be replaced with descriptions such as "output current from element A".

[0038] In addition, in this specification and the like, ordinal numbers such as "first", "second", "third", etc. are added to avoid confusion of constituent elements. Therefore, this ordinal number does not limit the number of constituent elements. In addition, this ordinal number does not limit the order of constituent elements. For example, a constituent element with "first" attached in one of the embodiments of this specification and the like may have "second" attached in other embodiments or claims. In addition, for example, in this specification and the like, the constituent element referred to as "first" in one embodiment may be omitted in the scope of other embodiments or claims.

[0039] In this specification, for convenience, phrases indicating configuration such as "above" and "below" are sometimes used to describe the positional relationship of constituent elements with reference to the drawings. In addition, the positional relationship of constituent elements is appropriately changed according to the directions in which the constituent elements are described. Therefore, without being limited to the phrases described in the specification and the like, the phrases can be appropriately changed according to the situation. For example, in the expression "insulator located on the top surface of a conductor", by rotating the direction of the shown drawing by 180°, it can also be referred to as "insulator located below the conductor".

[0040] In addition, terms such as "upper" or "lower" are not limited to the case where the positional relationship of the component is "directly above" or "directly below" and in direct contact. For example, in the expression "electrode B on insulating layer A", it is not necessarily required that electrode B is formed in direct contact on insulating layer A, and it may also include cases where other components are included between insulating layer A and electrode B.

[0041] In addition, in this specification and the like, depending on the situation, terms such as "film" and "layer" can be interchanged with each other. For example, sometimes "conductive layer" can be interchanged with "conductive film". In addition, sometimes "insulating film" can be changed to "insulating layer". In addition, depending on the situation or state, other terms can be used instead of terms such as "film" and "layer". For example, sometimes "conductive layer" or "conductive film" can be changed to "conductor". In addition, for example, sometimes "insulating layer" or "insulating film" can be changed to "insulator".

[0042] Note that in this specification and the like, terms such as "electrode" or "wiring" do not functionally limit their components. For example, sometimes "electrode" is used as part of "wiring", and vice versa. Furthermore, "electrode" or "wiring" also includes cases where multiple "electrodes" or "wirings" are formed integrally, etc.

[0043] In this specification and the like, depending on the situation or state, terms such as "wiring", "signal line", and "power line" can be interchanged with each other. For example, sometimes "wiring" can be changed to "signal line". In addition, for example, sometimes "wiring" can be changed to "power line". Vice versa, sometimes "signal line" or "power line" can be changed to "wiring". Sometimes "power line" can be changed to "signal line". Vice versa, sometimes "signal line" can be changed to "power line". In addition, depending on the situation or state, the "potential" applied to the wiring can be mutually changed to "signal". Vice versa, sometimes "signal" can be changed to "potential".

[0044] In the present specification and the like, impurities in a semiconductor refer to substances other than the main components constituting the semiconductor film. For example, an element with a concentration lower than 0.1 atomic% is an impurity. When impurities are included, for example, it is possible to form DOS (Density of States) in the semiconductor, and the carrier mobility may decrease or the crystallinity may decrease. When the semiconductor is an oxide semiconductor, as impurities that change the semiconductor characteristics, for example, there are Group 1 elements, Group 2 elements, Group 13 elements, Group 14 elements, Group 15 elements, or transition metals other than the main components. In particular, for example, there are hydrogen (also included in water), lithium, sodium, silicon, boron, phosphorus, carbon, nitrogen, etc. When the semiconductor is an oxide semiconductor, for example, the incorporation of impurities such as hydrogen sometimes causes the generation of oxygen defects. In addition, when the semiconductor is a silicon layer, as impurities that change the semiconductor characteristics, for example, there are oxygen, Group 1 elements other than hydrogen, Group 2 elements, Group 13 elements, Group 15 elements, etc.

[0045] In the present specification and the like, a switch refers to an element having a function of controlling whether current flows by changing to a conductive state (on state) or a non-conductive state (off state). Alternatively, a switch refers to an element having a function of selecting and switching current paths. As an example of a switch, an electrical switch or a mechanical switch, etc. can be used. In other words, as long as a switch can control current, it is not limited to a specific element.

[0046] Examples of electrical switches include transistors (such as bipolar transistors or MOS transistors), diodes (such as PN diodes, PIN diodes, Schottky diodes, metal-insulator-metal (MIM) diodes, metal-insulator-semiconductor (MIS) diodes, or diode-connected transistors), or logic circuits combining these elements, etc. When a transistor is used as a switch, the "conductive state" of the transistor refers to a state where the source electrode and the drain electrode of the transistor are electrically short-circuited. In addition, the "non-conductive state" of the transistor refers to a state where the source electrode and the drain electrode of the transistor are electrically disconnected. When a transistor is used only as a switch, there is no particular limitation on the polarity (conductivity type) of the transistor.

[0047] As an example of a mechanical switch, a switch using MEMS (Micro Electro Mechanical Systems) technology such as a digital micromirror device (DMD) can be cited. This switch has electrodes that can move mechanically, and operates by moving these electrodes to control conduction and non-conduction.

[0048] Advantages of the Invention

[0049] According to one aspect of the present invention, a novel semiconductor device can be provided. Further, according to one aspect of the present invention, a semiconductor device capable of reducing power consumption can be provided. Further, according to one aspect of the present invention, a semiconductor device capable of reducing the area can be provided. Further, according to one aspect of the present invention, a semiconductor device capable of achieving a large capacity of a storage device can be provided.

[0050] Note that the description of these effects does not preclude the existence of other effects. Further, one aspect of the present invention does not necessarily have all of the above effects. Further, effects other than the above effects can be obviously seen from the description of the specification, drawings, claims, etc., and effects other than the above effects can be extracted from the description.

[0051] BRIEF DESCRIPTION OF THE DRAWINGS

[0052] [FIG. 1] Figure 1A is a block diagram showing an example of the structure of a storage device. Figure 1B is a diagram for explaining an example of the hierarchy of storage areas in a storage device.

[0053] Figure 2 Figure 2 is a diagram for explaining an example of the hierarchy of storage areas in a storage device.

[0054] [FIG. 3] Figure 3A , Figure 3B1 and Figure 3B2 is a circuit diagram showing an example of the structure of a storage cell included in a storage device.

[0055] [FIG. 4] Figure 4A and Figure 4B is a diagram for explaining an example of the hierarchy of storage areas in a storage device.

[0056] Figure 5 Figure 5 is a block diagram showing an example of the structure of a storage device.

[0057] Figure 6 Figure 6 is a block diagram showing an example of the structure of a storage device.

[0058] Figure 7 Figure 7 is a block diagram showing an example of the structure of a storage device.

[0059] Figure 8 Figure 8 is a block diagram showing an example of the structure of a storage device.

[0060] Fig. 9 Fig. 9 ​​​​​​​​​​​​It is a block diagram showing an example of the structure of a storage device.

[0061] Fig.10 Fig.10 It is a block diagram showing an example of the structure of a memory cell array included in the storage device.

[0062] Fig.11 Fig.11 It is a block diagram showing an example of the structure of a memory cell array included in the storage device.

[0063] [Figure 12] Fig. 12A and Fig. 12B It is a diagram showing an example of the structure of a memory cell array included in the storage device.

[0064] Fig.13 Fig.13 It is a diagram showing an example of the structure of a memory cell array included in the storage device.

[0065] Fig.14 Fig.14 It is a cross-sectional view showing an example of the structure of a semiconductor device.

[0066] [Figure 15] Fig.15A , Fig. 15B and Fig. 15C It is a cross-sectional view showing an example of the structure of a transistor.

[0067] [Figure 16] Fig.16A It is a top view showing an example of the structure of a transistor, Fig. 16B and Fig. 16C It is a cross-sectional view showing an example of the structure of the transistor.

[0068] [Figure 17] Fig.17A It is a top view showing an example of the structure of a transistor, Fig. 17B and Fig. 17C It is a cross-sectional view showing an example of the structure of the transistor.

[0069] [Figure 18] Fig.18A It is a top view showing an example of the structure of a transistor, Fig.18B and Fig.18C It is a cross-sectional view showing an example of the structure of the transistor.

[0070] [Figure 19] Fig.19A It is a top view showing an example of the structure of a transistor, Fig.19B and Fig.19C It is a cross-sectional view showing an example of the structure of the transistor.

[0071] [Figure 20] Fig. 20A It is a top view showing an example of the structure of a transistor, Fig. 20B ​​​​​​​​and Fig. 20C is a cross-sectional view showing an example of the structure of the transistor.

[0072] [Figure 21] Fig.21A is a top view showing an example of the structure of the transistor, Fig. 21B is a perspective view showing an example of the structure of the transistor.

[0073] [Figure 22] Fig.22A and Fig. 22B is a cross-sectional view showing an example of the structure of the transistor.

[0074] [Figure 23] Fig.23A , Fig. 23B , Fig.23C , Fig.23D , Fig.23E , Fig.23F , Figure 23G and Fig.23H is a perspective view showing an example of an electronic device.

[0075] [Figure 24] Fig.24A and Fig. 24B is a perspective view showing an example of an electronic device.

[0076] Mode of implementing the invention

[0077] In this specification and the like, metal oxide refers to an oxide of a metal in a broad sense. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), and oxide semiconductors (Oxide Semiconductor, which may also be abbreviated as OS), etc. For example, when a metal oxide is used for the active layer of a transistor, the metal oxide is sometimes referred to as an oxide semiconductor. In other words, when a metal oxide can form a channel formation region of a transistor including at least one of an amplification function, a rectification function, and a switching function, the metal oxide is called a metal oxide semiconductor. In addition, an OS FET or an OS transistor may also be called a transistor including a metal oxide or an oxide semiconductor.

[0078] In addition, in this specification and the like, a metal oxide containing nitrogen may also be referred to as a metaloxide. In addition, a metal oxide containing nitrogen may also be called a metal oxynitride.

[0079] In addition, in this specification and the like, the structures shown in each embodiment can be appropriately combined with the structures shown in other embodiments to form one mode of the present invention. In addition, when multiple structural examples are shown in one embodiment, these structural examples can be appropriately combined.

[0080] In addition, the content (or a part thereof) described in a certain embodiment can be applied / combined / replaced with at least one of the content (or a part thereof) described in other content (or a part thereof) described in this embodiment and the content (or a part thereof) described in another or multiple other embodiments (another or multiple other examples).

[0081] Note that the content described in the embodiments refers to the content described by using various drawings in each embodiment (or example) or the content described by using the articles described in the specification.

[0082] In addition, by combining the drawing (or a part thereof) shown in a certain embodiment with at least one of the other parts of this drawing, the other drawings (or a part thereof) shown in this embodiment, and the drawings (or a part thereof) shown in another or multiple other embodiments, more drawings can be formed.

[0083] The embodiments described in this specification are described with reference to the drawings. Note that those of ordinary skill in the art can easily understand the fact that the embodiments can be implemented in multiple different forms, and their modes and detailed contents can be changed into various forms without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited only to the content described in the embodiments. Note that in the structure of the invention in the embodiments, the same reference numerals are sometimes used in different drawings to represent the same parts or parts having the same functions, and repeated descriptions are omitted. In drawings such as perspective views, sometimes the illustration of some constituent elements is omitted for clarity.

[0084] In the drawings of this specification, for the sake of clear illustration, sometimes the sizes, layer thicknesses, or regions are exaggerated. Therefore, the present invention is not limited to the dimensions in the drawings. In addition, in the drawings, ideal examples are schematically shown, so the present invention is not limited to the shapes, numerical values, etc. shown in the drawings. For example, it may include unevenness of signals, voltages, or currents caused by noise, timing deviations, etc.

[0085] (Embodiment 1)

[0086] In this embodiment, an example of the structure according to one mode of the present invention is described.

[0087] <Structural example of a semiconductor device>

[0088] Figure 1AAn example of the structure of a semiconductor device 11 showing one aspect of the present invention. The semiconductor device 11 includes storage circuits 210, 220, 230, and 240 that constitute a storage device, and a control circuit 20.

[0089] In addition, although Figure 1A not shown, the semiconductor device 11 includes an integrated circuit (for example, a CPU, a GPU, etc.), the storage circuit 210 may also be included in the integrated circuit, and furthermore, the storage circuit 220 may also be included in the integrated circuit.

[0090] In addition, the storage circuit 220 may apply DOSRAM (Dynamic Oxide Semiconductor Random Access Memory) (registered trademark), and the storage circuit 230 may apply NOSRAM (Dynamic Oxide Semiconductor Random Access Memory) (registered trademark). DOSRAM and NOSRAM will be described in detail later.

[0091] Figure 1B is a diagram showing an example of the storage circuits of the storage device included in the semiconductor device 11 presented hierarchically. Figure 1A of the semiconductor device 11 presented hierarchically.

[0092] In Figure 1B the storage circuits of the storage device included in the semiconductor device 11 are hierarchically arranged in order of access speed. The storage circuit 210 is represented as the topmost level, the storage circuit 220 is represented as the level below the storage circuit 210, the storage circuit 230 is represented as the level below the storage circuit 220, and the storage circuit 240 is represented as the bottommost level.

[0093] Note that in this specification, etc., the storage circuits of the storage device included in the semiconductor device 11 are sequentially referred to as the first storage area 110, the second storage area 120, the third storage area 130, and the fourth storage area 140 from the topmost level. In particular, the first storage area 110 is regarded as a storage area such as a register, the second storage area 120 is regarded as a storage area of a cache memory, the third storage area 130 is regarded as a storage area of a main storage device (main memory), and the fourth storage area 140 is regarded as a storage area of an auxiliary storage device.

[0094] The storage circuit 210 of the first storage area 110 holds the results and states of arithmetic processing in an integrated circuit, etc. Therefore, the storage circuit 210 is electrically connected to the storage circuit 220 and the storage circuit 230 to transmit and receive data required for arithmetic processing.

[0095] The storage circuit 210 that can be used for the first storage area 110 includes, for example, registers, flip-flops, SRAM (Static Random Access Memory), etc.

[0096] Since the second storage area 120 is used as the storage area of the cache memory, part of the data is copied from the storage circuit 230 used as the main storage device in the third storage area 130 and stored. Thus, the storage circuit 220 is electrically connected to the storage circuit 230.

[0097] In addition, since the second storage area 120 corresponds to the storage area of the cache memory, the second storage area 120 can also be divided into multiple levels. For example, Figure 2 shows a case where the storage circuit 220 is further divided into three levels. Figure 2 The storage circuit 220 in includes the storage areas of cache memories 121 to 123. The cache memory 121 (primary cache memory, L1 cache memory) is provided at the lower level of the first storage area 110. The cache memory 122 (secondary cache memory, L2 cache memory) is provided at the lower level of the cache memory 121. The cache memory 123 (tertiary cache memory, L3 cache memory) is provided at the lower level of the cache memory 122.

[0098] In addition, the number of levels of the second storage area 120 is not limited to this. That is, the second storage area 120 can be composed of one level, two levels, or four or more levels.

[0099] The storage circuit 240 that can be used for the fourth storage area 140 is electrically connected to the storage circuit 230 to store the data input from the storage circuit 230 in the third storage area.

[0100] As the storage circuit 240 that can be used for the fourth storage area 140, for example, it can include a non-volatile memory, etc. As the non-volatile memory, for example, flash memory, hard disk drive, solid state drive, etc. can be cited.

[0101] The control circuit 20 is electrically connected to the storage circuit 220 and the storage circuit 230. The control circuit 20 has a function of changing the storage area of each level of the second storage area 120 and the third storage area 130 in the semiconductor device 11.

[0102] The storage circuits in the higher levels need to operate at higher speeds. In addition, the storage devices in the lower levels need to have larger capacities and higher densities (or smaller areas per bit). For example, in the first storage area 110, it is necessary to operate at a particularly high speed because it stores data used in operations in integrated circuits and the like. In addition, for example, the top-level first-level cache memory in the second storage area 120 needs to operate at a high speed because it is accessed most frequently. On the other hand, although the second-level cache memory, the third-level cache memory, etc. do not need to achieve the same high speed as the first-level cache memory, they need to achieve a large capacity and have a smaller area per bit than the first-level cache memory.

[0103] In addition, since the storage circuit is in a higher level, the number of data rewrites (or refresh times) for the storage device is larger. Therefore, the data retention time can be shortened as a specification of the storage device. On the other hand, since the storage device is in a lower level, the number of data rewrites (or refresh times) for the storage device is smaller, and it is necessary to extend the data retention time as a specification of the storage device.

[0104] One aspect of the present invention changes the data retention time of the storage devices in each level according to the usage of the semiconductor device to increase or decrease the storage areas in each level. That is, the storage device or semiconductor device according to one aspect of the present invention can change the performance of each level of the storage device according to the usage.

[0105] <Circuit structure examples of DOSRAM and NOSRAM>

[0106] Next, the circuit structures of the storage cells of DOSRAM that can be used for the storage circuit 220 and NOSRAM that can be used for the storage circuit 230 will be described.

[0107] Note that the low-level potential and high-level potential used in the following description do not mean specific potentials, and the specific potentials may be different if the wirings are different. For example, the low-level potential and high-level potential applied to the wiring WOL may be different from the low-level potential and high-level potential applied to the wiring BIL, respectively.

[0108] Figure 3A An example of the circuit structure of the storage cell of DOSRAM is shown. The storage cell 221 includes a transistor M1 and a capacitor CA. In addition, the transistor M1 includes a front gate (sometimes simply referred to as a gate) and a back gate.

[0109] The first terminal of the transistor M1 is connected to the first terminal of the capacitor CA, the second terminal of the transistor M1 is connected to the wiring BIL, the gate of the transistor M1 is connected to the wiring WOL, and the back gate of the transistor M1 is connected to the wiring BGL. The second terminal of the capacitor CA is connected to the wiring CAL.

[0110] The transistor M1 is used as a write transistor in the memory cell 221. Additionally, this write transistor is preferably the following OS transistor.

[0111] The wiring BIL is used as a bit line, and the wiring WOL is used as a word line. The wiring CAL is used as a wiring for applying a predetermined potential to the second terminal of the capacitor CA. During data writing and reading, the wiring CAL is preferably applied with a low-level potential (sometimes also referred to as a reference potential).

[0112] The wiring BGL is used as a wiring for applying a potential to the back gate of the transistor M1. By applying an arbitrary potential to the wiring BGL, the threshold voltage of the transistor M1 can be increased or decreased.

[0113] Data writing and reading are performed by applying a high-level potential to the wiring WOL to turn on the transistor M1, thereby making the connection between the wiring BIL and the first terminal of the capacitor CA conductive.

[0114] Specifically, a potential corresponding to the data to be written is applied to the wiring BIL, and the potential is written to the first terminal of the capacitor CA through the transistor M1 for data writing. After writing the data, by applying a low-level potential to the wiring WOL to turn off the transistor M1, the potential can be held in the memory cell 221.

[0115] Furthermore, when reading data, first the wiring BIL is precharged to an appropriate potential, for example, precharged to a potential intermediate between the low-level potential and the high-level potential, and then the wiring BIL is made electrically floating. Then, a high-level potential is applied to the wiring WOL to turn on the transistor M1, thereby changing the potential of the wiring BIL. Since the change in the potential of the wiring BIL depends on the potential written to the first terminal of the capacitor CA, the data held in the memory cell 221 can be read from the changed potential of the wiring BIL.

[0116] In addition, the above-mentioned memory cell 221 is not limited to Figure 3A the circuit structure shown, and the circuit structure of the memory cell 221 can also be appropriately changed.

[0117] Figure 3B1 An example of the circuit structure of a memory cell of a NOSRAM is shown. The memory cell 231 includes a transistor M2, a transistor M3, and a capacitor CB. Additionally, the transistor M2 includes a front gate (sometimes simply referred to as a gate) and a back gate.

[0118] The transistor M2 is used as a write transistor in the memory cell 231. Additionally, this write transistor is preferably the following OS transistor.

[0119] In addition, the transistor M3 is used as a read transistor in the memory cell 231. This read transistor is preferably an OS transistor or a transistor in which the semiconductor layer contains silicon. In addition, in this working example, unless otherwise specified, the transistor M3 operates in the saturation region. That is, appropriate biasing is applied to the gate voltage, source voltage, and drain voltage of the transistor M3 so that the transistor operates in the saturation region.

[0120] The first terminal of the transistor M2 is connected to the first terminal of the capacitor CB, the second terminal of the transistor M2 is connected to the wiring WBL, the gate of the transistor M2 is connected to the wiring WOL, and the back gate of the transistor M2 is connected to the wiring BGL. The second terminal of the capacitor CB is connected to the wiring CAL. The first terminal of the transistor M3 is connected to the wiring RBL, the second terminal of the transistor M3 is connected to the wiring SL, and the gate of the transistor M3 is connected to the first terminal of the capacitor CB.

[0121] The wiring WBL serves as a write bit line, the wiring RBL serves as a read bit line, and the wiring WOL serves as a word line. The wiring CAL serves as a wiring for applying a predetermined potential to the second terminal of the capacitor CB. When holding data, it is preferable to apply a low-level potential (sometimes referred to as a reference potential) to the wiring CAL, and when writing and reading data, it is preferable to apply a high-level potential to the wiring CAL.

[0122] The wiring BGL serves as a wiring for applying a potential to the back gate of the transistor M2. By applying an arbitrary potential to the wiring BGL, the threshold voltage of the transistor M2 can be increased or decreased.

[0123] Data is written by applying a high-level potential to the wiring WOL to make the transistor M2 conductive and making the wiring WBL and the first terminal of the capacitor CB conductive. Specifically, when the transistor M2 is conductive, a potential corresponding to the information to be recorded is applied to the wiring WBL to write this potential to the first terminal of the capacitor CB and the gate of the transistor M3. Then, a low-level potential is applied to the wiring WOL to make the transistor M2 non-conductive, thereby holding the potential of the first terminal of the capacitor CB and the potential of the gate of the transistor M3.

[0124] Data is read by applying a predetermined potential to the wiring SL. Since the current flowing between the source and drain of the transistor M3 and the potential of the first terminal of the transistor M3 are determined by the potential of the gate of the transistor M3 and the potential of the second terminal of the transistor M3, the potential held by the first terminal of the capacitor CB (or the gate of the transistor M3) can be read by reading the potential of the wiring RBL connected to the first terminal of the transistor M3. That is, the information written in this memory cell can be read from the potential held by the first terminal of the capacitor CB (or the gate of the transistor M3).

[0125] In addition, the above storage unit 231 is not limited to Figure 3B1 the circuit structure shown. The circuit structure of the storage unit 231 can be appropriately changed. For example, a structure in which the wiring WBL and the wiring RBL are combined into one wiring BIL can also be adopted. Figure 3B2 An example of the circuit structure of the storage unit in this case is shown. In the storage unit 232, the wiring WBL and the wiring RBL of the storage unit 231 are combined into one wiring BIL, and the second terminal of the transistor M2 and the first terminal of the transistor M3 are connected to the wiring BIL. That is, the storage unit 232 operates by combining the write bit line and the read bit line into one wiring BIL.

[0126] As described above, DOSRAM and NOSRAM are storage devices including an OS transistor used as a write transistor. The semiconductor layer of the OS transistor includes the metal oxide described in Embodiment 3. As the metal oxide, for example, one or more materials selected from indium, element M (element M is aluminum, gallium, yttrium, or tin), and zinc can be used. In particular, when the semiconductor layer contains a metal oxide composed of indium, gallium, and zinc, the bandgap of the semiconductor layer can be increased. Therefore, the off-state current of the OS transistor can be reduced.

[0127] <Method for changing the storage area of each level of the storage device>

[0128] The OS transistor can include a back gate by adopting the structure described in Embodiment 3. In the OS transistor including a back gate, the threshold voltage of the OS transistor can be changed by applying a potential to the back gate. For example, when the OS transistor is an n-channel transistor, the threshold voltage of the OS transistor can be fluctuated to the negative side by applying a positive potential to the back gate, and conversely, the threshold voltage of the OS transistor can be fluctuated to the positive side by applying a negative potential to the back gate.

[0129] By fluctuating the threshold voltage of the OS transistor, the off-state current of the OS transistor can be increased or decreased. When the off-state current of the OS transistor is increased, the charge movement speed between the source and drain of the OS transistor corresponding to the held data becomes faster, and the data holding time is shortened, thereby improving the operating speed (sometimes referred to as the drive frequency) of the OS transistor. In addition, when the off-state current of the OS transistor is decreased, the charge movement speed between the source and drain of the OS transistor corresponding to the held data becomes slower, and the data holding time is extended, thereby reducing the operating speed of the OS transistor. That is, by fluctuating the threshold voltage of the OS transistor, the data holding time and the operating speed can be adjusted.

[0130] Here, consider the case where the above DOSRAM is adopted as the storage circuit 220 of the semiconductor device 11, and the above NOSRAM is adopted as the storage circuit 230. For example, in Figure 1A and Figure 1B of the semiconductor device 11, when the storage capacity of the storage circuit 210 used as the first storage area is insufficient and the storage capacity of the storage circuit 220 used as the second storage area 120 remains, as Figure 4A shown, by reducing the threshold voltage of the OS transistors included in a part of the storage circuit 220a of the storage circuit 220, shortening the data retention time of the storage circuit 220a, and increasing the operating speed, the storage circuit 220a can be used as the first storage area 110.

[0131] Specifically, when the transistor M1 in the storage cell 221 of the storage circuit 220a is operated in such a manner that the potential range applied to the gate is -0.8 V or more and 2.5 V or less, for example, by applying a voltage of -1.5 V or more and less than 1.5 V to the back gate of the transistor M1, the storage circuit 220a can be used as the first storage area 110.

[0132] In addition, for example, in Figure 1A and Figure 1B of the semiconductor device 11, when the storage capacity of the storage circuit 230 used as the third storage area 130 is insufficient and the storage capacity of the storage circuit 220 used as the second storage area 120 remains, as Figure 4A shown, by increasing the threshold voltage of the OS transistors included in a part of the storage circuit 220b of the storage circuit 220, extending the data retention time of the storage circuit 220b, and reducing the operating speed, the storage circuit 220b can be used as the third storage area 130.

[0133] Specifically, when the transistor M1 in the storage cell 221 of the storage circuit 220b is operated in such a manner that the potential range applied to the gate is -0.8 V or more and 2.5 V or less, for example, by applying a voltage of -7.5 V or more and less than -4.5 V to the back gate of the transistor M1, the storage circuit 220a can be used as the third storage area 130.

[0134] In addition, in Figure 1A and Figure 1B of the semiconductor device 11, without changing the storage area of the storage circuit 220 to another level, that is, when the storage circuit 220 operates normally as the second storage area 120, for example, a voltage of -4.5 V or more and less than -1.5 V is applied to the back gate of the transistor M1 under the condition that the potential range applied to the gate of the transistor M1 is -0.8 V or more and 2.5 V or less.

[0135] In addition, for example, in the semiconductor device 11 of Figure 1A and Figure 1B when the storage capacity of the storage circuit 220 serving as the second storage area 120 is insufficient and the storage capacity of the storage circuit 230 serving as the third storage area 130 remains, as Figure 4B shown, the threshold voltage of the OS transistor included in a part of the storage circuit 230, i.e., the storage circuit 230a, is reduced, and the data retention time of the storage circuit 230a is shortened, whereby the storage circuit 230a can be used as the second storage area 120.

[0136] Specifically, when the transistor M2 in the storage cell 231 (storage cell 232) of the storage circuit 230a is operated in such a manner that the potential range applied to the gate is -0.8 V or more and 2.5 V or less, for example, by applying a voltage of -4.5 V or more and less than -1.5 V to the back gate of the transistor M2, the storage circuit 230a can be used as the second storage area 120.

[0137] For example, in the semiconductor device 11 of Figure 1A and Figure 1B when the storage capacity of the storage circuit 240 serving as the fourth storage area 140 is insufficient and the storage capacity of the storage circuit 230 serving as the third storage area 130 remains, as Figure 4B shown, the threshold voltage of the OS transistor included in a part of the storage circuit 230, i.e., the storage circuit 230b, is increased, and the data retention time of the storage circuit 230b is extended, whereby the storage circuit 230b can be used as the fourth storage area 140.

[0138] Specifically, when the transistor M2 in the storage cell 231 (storage cell 232) of the storage circuit 230b is operated in such a manner that the potential range applied to the gate is -0.8 V or more and 2.5 V or less, for example, by applying a voltage lower than -7.5 V to the back gate of the transistor M2, the storage circuit 230b can be used as the fourth storage area 140.

[0139] In addition, in the semiconductor device 11 of Figure 1A and Figure 1B without changing the storage area of the storage circuit 230 to another level, that is, when the storage circuit 230 operates normally as the third storage area 130, for example, a voltage of -7.5 V or more and less than -4.5 V is applied to the back gate of the transistor M1 under the condition that the potential range applied to the gate of the transistor M1 is -0.8 V or more and 2.5 V or less.

[0140] Furthermore, the voltage ranges applied to the gates of each of the transistor M1 of the memory cell 221 and the transistor M2 of the memory cells 231 (memory cells 232) can be made almost the same. Specifically, the circuits that generate the positive voltage (or negative voltage) applied to the gates of each of the transistor M1 and the transistor M2 can be the same. As a result, it is not necessary to provide a large number of circuits for generating the voltages applied to the gates of the transistor M1 and the transistor M2, thereby reducing the power consumption of the semiconductor device 11. In particular, when a negative voltage is applied to the gate of the transistor, the generation of this negative voltage sometimes increases the power consumption. Therefore, the generation circuits (for example, a charge pump circuit, etc.) for applying the negative voltage to the gates of each of the transistor M1 and the transistor M2 are preferably used in common.

[0141] The above voltage ranges applied to the gate and the back gate of the transistor M1 (transistor M2) are an example. Since in all semiconductor devices, the materials, structures, etc. of the semiconductor layers of the transistors included in the semiconductor device cause variations in transistor characteristics, the voltage ranges applied to the gate and the back gate need to be set as required according to the circumstances.

[0142] In addition, in all semiconductor devices, the characteristics of the transistors sometimes vary according to the environment in which the semiconductor device is driven. Specifically, the higher the temperature of the environment in which the semiconductor device is driven, the larger the drain current corresponding to the gate-source voltage of the transistor, and the higher the driving frequency of the transistor. That is to say, the performance of the semiconductor device sometimes varies according to the temperature of the environment. Therefore, it is more preferable for the semiconductor device to adopt the following structure, that is, by varying the voltage applied to the back gate of the OS transistor of the write transistor according to the temperature of the environment, the characteristics of the transistor are appropriately adjusted. That is to say, by applying voltages corresponding to the temperature of the environment in which the semiconductor device 11 is driven to the back gates of the transistors M1 and M2 included in each of the memory cell 221 and the memory cells 231 (memory cells 232), each of the memory circuits 220 and 230 can operate suitable for the temperature of this environment.

[0143] <Control circuit 20>

[0144] Next, the circuit structure for controlling the threshold voltage of the write transistors (corresponding to the transistor M1 in Figure 3A and the transistor M2 in Figure 3B1 and Figure 3B2 ) included in each of the memory circuits 220 and 230 will be described.

[0145] Figure 5 is a block diagram showing the control circuit 20 for controlling the threshold voltage of the write transistor. In addition, in Figure 5In order to illustrate the electrical connection with the storage device, a storage unit 30 including a storage circuit 220 and a storage circuit 230 is also illustrated.

[0146] The control circuit 20 includes a control unit 21, voltage generation circuits 22[1] to voltage generation circuits 22[P] (P is an integer of 1 or more), a circuit 23A, a circuit 23B, and a temperature detection circuit 25. In addition, when the potential of the back gate is not fluctuated according to the ambient temperature, the control circuit 20 may adopt a configuration that does not include the temperature detection circuit 25.

[0147] The control unit 21 is electrically connected to the storage unit 30, the voltage generation circuits 22[1] to voltage generation circuits 22[P], the circuit 23A, the circuit 23B, and the temperature detection circuit 25. Each of the voltage generation circuits 22[1] to voltage generation circuits 22[P] is electrically connected to the circuit 23A and the circuit 23B. The circuit 23A is electrically connected to the storage circuit 220 through a plurality of wirings BGL1, and the circuit 23B is electrically connected to the storage circuit 230 through a plurality of wirings BGL2.

[0148] The storage unit 30 has a function of sending a signal related to the usage state of each of the storage circuit 220 and the storage circuit 230 (for example, the ratio of the used storage capacity to all storage capacities, etc.) to the control unit 21. According to this usage state, the control unit 21 sends signals to each circuit included in the control circuit 20 by receiving this signal to change the allocation of each layer of the storage unit 30 (for example, Figure 1B the first storage area 110, the second storage area 120, the third storage area 130, the fourth storage area 140 shown). Specifically, the control unit 21 sends signals to the voltage generation circuits 22[1] to voltage generation circuits 22[P], the circuit 23A, and the circuit 23B.

[0149] Each of the voltage generation circuits 22[1] to voltage generation circuits 22[P] has a function of generating a voltage applied to the back gate of the write transistor. In addition, the voltage generation circuits 22[1] to voltage generation circuits 22[P] have a function of starting or stopping the generation of this voltage according to a signal from the control unit 21. Due to this function, it is possible to drive only the voltage generation circuits that generate the voltages required for the allocation of each layer of the storage unit 30 and stop the unnecessary voltage generation circuits. As a result, it is possible to drive only the required circuits among the voltage generation circuits 22[1] to voltage generation circuits 22[P], thereby reducing the power consumption of the control circuit 20.

[0150] In addition, as a circuit for generating a negative voltage among the voltage generation circuits 22[1] to voltage generation circuits 22[P], for example, a charge pump circuit can be used.

[0151] The circuit 23A has a function of selectively applying voltages generated from each of the voltage generation circuits 22[1] to 22[P] to each of the plurality of wirings BGL1. Additionally, the voltages selected with respect to the plurality of wirings BGL1 depend on the signals sent from the control unit 21. Due to this function, a specified voltage can be applied to the back gates of the write transistors included in the memory circuit 220 from the wiring BGL1, and the memory circuit 220 can be divided into regions corresponding to the respective allocated levels. For example, when the memory circuit 220 is divided into p levels (where p is an integer greater than or equal to 2 and less than or equal to P), the circuit 23A applies p kinds of voltages to the plurality of wirings BGL1 to divide the memory circuit 220 into p regions.

[0152] Similarly, the circuit 23B has a function of selectively applying voltages generated from each of the voltage generation circuits 22[1] to 22[P] to each of the plurality of wirings BGL2. Additionally, the voltages selected with respect to the plurality of wirings BGL2 depend on the signals sent from the control unit 21. Due to this function, a specified voltage can be applied to the back gates of the write transistors included in the memory circuit 230 from the wiring BGL2, and the memory circuit 230 can be divided into regions corresponding to the allocated levels.

[0153] <Working Example>

[0154] Here, a working example of the control circuit 20 is described. Additionally, in this working example, a case where the potential of the back gate does not fluctuate according to the ambient temperature is described.

[0155] As an initial stage of the working example, consider the following situation. For example, as Figure 6 shown, as the usage state of the storage unit 30, the entire storage capacity of the memory circuit 220 to which the second storage area 120 is allocated is used to hold data, and a partial storage capacity of the memory circuit 230 to which the third storage area 130 is allocated is used to hold data. Note that at this time, the voltage generation circuit 22[p1] (where p1 is an integer greater than or equal to 1 and less than or equal to P) generates a voltage applied to the back gate of the write transistor included in the memory cell of the memory circuit 220 that is used as the memory cell of the second storage area 120, and the voltage generation circuit 22[p2] (where p2 is an integer greater than or equal to 1 and less than or equal to P and different from p1) generates a voltage applied to the back gate of the write transistor included in the memory cell of the memory circuit 230 that is used as the memory cell of the third storage area 130.

[0156] In this case, when the storage unit 30 determines that the storage capacity of the second storage area 120 is insufficient, the storage unit 30 sends a signal Sig1 to the control unit 21 to notify that the entire storage capacity of the memory circuit 220 is in use state and the memory circuit 230 partially has storage space.

[0157] The control unit 21 sends the signal Sig2 to the voltage generation circuits 22[1] to 22[P] and sends the signal Sig3 to the circuit 23B by receiving this signal. The signals Sig2 and Sig3 are signals for allocating the second storage area 120 to the storage circuit 230.

[0158] Specifically, the signal Sig2 can be a signal for selecting a circuit that generates a voltage applied to the back gate of the write transistor included in the specified area of the storage circuit 230 in order to allocate the second storage area 120 to the specified area. Note that here, as this circuit, the voltage generation circuit 22[p3] (p3 is an integer greater than or equal to 1 and less than or equal to P and different from p2) is selected. The voltage generation circuit 22[p3] can be either the same circuit as the voltage generation circuit 22[p1] or a different circuit.

[0159] In addition, as described above, the voltage generation circuits not selected by the signal Sig2 can be stopped. For example, by using a switching element or the like to make the electrical connection between the voltage generation circuit and the wiring for supplying the drive voltage non-conductive, the voltage generation circuit can be stopped. Thereby, only the required voltage generation circuits can be driven, and thus the power consumption of the control circuit 20 can be reduced.

[0160] Furthermore, the signal Sig3 can be a signal including an instruction to apply the voltage generated by the voltage generation circuit 22[p3] to the BGL2 of the write transistor electrically connected to the specified area of the storage circuit 230. In addition, the signal Sig3 can also include an instruction to continue applying the voltage generated by the voltage generation circuit 22[p2] to the back gate of the write transistor included in the area of the third storage area 130 of the storage circuit 230.

[0161] By sending the signal Sig3 to the circuit 23B, the voltage generated by the voltage generation circuit 22[p3] can be applied to the back gate of the write transistor in the area of the storage circuit 230 where the second storage area 120 is reallocated. Thereby, the second storage area 120 can be allocated to the specified area of the storage circuit 230. Figure 7 The shown block diagram shows Figure 6 a subsequent step of the shown block diagram, which shows an example in which the entire area of the remaining storage capacity in the storage circuit 230 of the storage unit 30 is allocated to the second storage area 120 by sending the signal Sig3 to the circuit 23B.

[0162] <Temperature control>

[0163] Next, a method of changing the potential applied to the back gates of the write transistors (transistors M1, M2) of the storage unit 30 according to the ambient temperature will be described.

[0164] As an example, the temperature detection circuit 25 may adopt Figure 8 the structure shown. In addition, to illustrate the electrical connection structure with the temperature detection circuit 25, Figure 8 the control unit 21, the voltage generation circuit 22[1], the voltage generation circuit 22[P], the circuit 23A, and the wiring BGL1 are also shown. In addition, the circuit 23B, the wiring BGL2, and the storage unit 30 are omitted.

[0165] The temperature detection circuit 25 includes a temperature sensor 25a, an analog-to-digital conversion circuit 25b, and a voltage control circuit 25c.

[0166] The temperature sensor 25a has a function of sensing the temperature near the semiconductor device 11 and outputting an analog signal corresponding to the temperature. The output analog signal is sent to the analog-to-digital conversion circuit 25b. As the temperature sensor 25a, for example, a temperature-dependent resistor such as platinum, nickel, or copper, a thermistor, a thermocouple, an IC temperature sensor, etc. can be used.

[0167] The analog-to-digital conversion circuit 25b has a function of converting an analog imaging signal into a digital signal. The digital signal is sent to the voltage control circuit 25c.

[0168] The voltage control circuit 25c has a function of generating a correction voltage based on the digital signal. For example, the voltage control circuit 25c includes a storage device storing a correspondence table associating the digital signal and the correction voltage and a circuit for generating the correction voltage, and reads the magnitude of the correction voltage according to the digital signal sent from the analog-to-digital conversion circuit 25b. After reading the magnitude of the correction voltage, the correction voltage is generated by the circuit for generating the correction voltage, and the correction voltage is sent to the circuit 23A and the circuit 23B through the control unit 21. In addition, in Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 、 the temperature detection circuit 25 is electrically connected to the control unit 21, but the temperature detection circuit 25 may also be directly electrically connected to the circuit 23A and the circuit 23B.

[0169] Here, the circuit 23A (circuit 23B) includes a plurality of capacitors CF, and one of the two pairs of electrodes of the plurality of capacitors CF is electrically connected to the plurality of wirings BGL1 (plurality of wirings BGL2). The correction voltage sent to the circuit 23A (circuit 23B) is applied to the other of the two pairs of electrodes of the capacitor CF.

[0170] The circuit 23A (circuit 23B) includes an internal circuit 23IN. The internal circuit 23IN has a function of applying the various voltages generated by the voltage generation circuits 22[1] to 22[P] to each of the plurality of wirings BGL1 (plurality of wirings BGL2) according to a signal received from the control unit 21 by receiving the signal.

[0171] When changing the potential of the back gate according to the temperature of the environment, first, the internal circuit 23IN applies a potential to the plurality of wirings BGL1 (plurality of wirings BGL2), and then a correction voltage is applied to the other of the two pairs of electrodes of the capacitor. Thus, due to the capacitive coupling of the capacitor CF connected to them, the potential of the plurality of wirings BGL1 (plurality of wirings BGL2) fluctuates according to the correction voltage. In this way, the semiconductor device 11 can correct the characteristics of the write transistors of the storage unit 30 according to the temperature of the environment by including the temperature detection circuit 25.

[0172] Note that one mode of the present invention is not limited to the circuit structure described in the present embodiment and can be appropriately changed.

[0173] In addition, the present embodiment can be appropriately combined with other embodiments shown in this specification.

[0174] (Embodiment 2)

[0175] In the present embodiment, a structural example of the memory cell array 40 and its peripheral circuit that constitute the DOSRAM, NOSRAM, etc. described in the above embodiment will be described. Note that in the present embodiment, the memory cell array 40 and its peripheral circuit are collectively referred to as the storage device 200.

[0176] <Structural Example of Storage Device>

[0177] Fig. 9 An example of the structure of the storage device is shown. The storage device 200 includes a peripheral circuit 50 and a memory cell array 40. The peripheral circuit 50 includes a row decoder 53, a word line driver circuit 51, a bit line driver circuit 52, an output circuit 54, and a control logic circuit 56. In addition, Fig. 9 The control circuit 20 described in Embodiment 1 is also shown.

[0178] The bit line driving circuit 52 includes a column decoder 52a, a precharge circuit 52b, a sense amplifier 52c, and a write circuit 52d. The precharge circuit 52b has a function of precharging wirings SL, CAL, BIL, etc. The sense amplifier 52c has a function of amplifying data signals read from the wirings BIL and RBL. In addition, the wirings SL, CAL, and RBL are wirings connected to the memory cells in the memory cell array 40, which will be described in detail later. The amplified data signal is output as a digital data signal RDATA to the outside of the memory device 200 through the output circuit 54.

[0179] A low power supply voltage (VSS) as a power supply voltage, a high power supply voltage (VDD) for the peripheral circuit 50, and a high power supply voltage (VIL) for the memory cell array 40 are supplied to the memory device 200 from the outside.

[0180] Control signals (CE, WE, RE), an address signal ADDR, and a data signal WDATA are also input to the memory device 200 from the outside. The address signal ADDR is input to the row decoder 53 and the column decoder 52a, and the WDATA is input to the write circuit 52d.

[0181] The control logic circuit 56 processes input signals (CE, WE, RE) from the outside to generate control signals for the row decoder 53 and the column decoder 52a. CE is a chip enable signal, WE is a write enable signal, and RE is a read enable signal. The signals processed by the control logic circuit 56 are not limited to these, and other control signals can also be input as needed.

[0182] Each of the above circuits or signals can be appropriately used or omitted as needed.

[0183] Preferably, in addition to the memory cell array 40, the peripheral circuit 50 is also composed of OS transistors. Thus, the peripheral circuit 50 and the memory cell array 40 can be manufactured by the same manufacturing process, thereby reducing the manufacturing cost of the memory device 200.

[0184] <Example of the structure of the memory cell array>

[0185] Fig.10 The detailed structure of the memory cell array 40 in the case where DOSRAM is applied as a memory cell is shown. One column in the memory cell array 40 includes m (m is an integer of 1 or more), one row includes n (n is an integer of 1 or more), and a total of m×n memory cells 221 are included. The memory cells 221 are arranged in a row and column shape. Fig.10also represents the address of the storage unit 221 and shows the storage units located at the addresses [1, 1], [m, 1], [i, j], [1, n], [m, n] (where i is an integer greater than or equal to 1 and less than or equal to m, and j is an integer greater than or equal to 1 and less than or equal to n). Additionally, in the structure of the storage unit 221, the number of wirings WOL connecting the storage cell array 40 and the word line driver circuit 51 is m ([ Fig.10 only shows the wiring WOL[1], the wiring WOL[i], the wiring WOL[m]), and the number of wirings BGL connecting the storage cell array 40 and the control circuit 20 is also m ([ Fig.10 only shows the wiring BGL[1], the wiring BGL[i], the wiring BGL[m]). In addition, the number of wirings BIL connecting the storage cell array 40 and the bit line driver circuit 52 is n ([ Fig.10 only shows the wiring BIL[1], the wiring BIL[j], the wiring BIL[n]).

[0186] In addition, Fig.11 shows the detailed structure of the storage cell array 40 when NOSRAM is applied as the storage unit. One column in the storage cell array 40 includes m (m is an integer greater than or equal to 1) and one row includes n (n is an integer greater than or equal to 1), and there are a total of m×n storage units 231. The storage units 231 are configured in a row-column pattern. Fig.11 also represents the address of the storage unit 231 and shows the storage units located at the addresses [1, 1], [m, 1], [i, j], [1, n], [m, n] (where i is an integer greater than or equal to 1 and less than or equal to m, and j is an integer greater than or equal to 1 and less than or equal to n). Additionally, in the structure of the storage unit 231, the number of wirings WOL connecting the storage cell array 40 and the word line driver circuit 51 is m ([ Fig.11 only shows the wiring WOL[1], the wiring WOL[i], the wiring WOL[m]), and the number of wirings BGL connecting the storage cell array 40 and the control circuit 20 is also m ([ Fig.11 only shows the wiring BGL[1], the wiring BGL[i], the wiring BGL[m]). Additionally, although the number of wirings of the wiring CAL is shown as m ([ Fig.11 only shows the wiring CAL[1], the wiring CAL[i], the wiring CAL[m]), the object connected to the storage unit 231 through the wiring CAL is omitted. In addition, the respective numbers of the wirings RBL, WBL, and SL connecting the storage cell array 40 and the bit line driver circuit 52 are n ([ Fig.11 only shows the wiring RBL[1], the wiring RBL[j], the wiring RBL[n], the wiring WBL[1], the wiring WBL[j], the wiring WBL[n], the wiring SL[1], the wiring SL[j], the wiring SL[n]).

[0187] In Fig.10 and Fig.11 in the memory cell array 40 shown, since wirings BGL[1] to BGL[m] are respectively provided for each row, the regions of the respective layers of the memory device described in Embodiment 1 are changed in each row. In addition, the configuration of the wiring BGL electrically connected to the back gate of the transistor M1 (transistor M2) of the memory cell 221 (memory cell 231) included in the memory cell array 40 is not limited to Fig.10 and Fig.11 the configuration shown. For example, a wiring BGL may be provided for each of the transistors M1 (transistors M2) of the plurality of memory cells 221 (memory cells 231), and the regions of the respective layers of the memory device may also be changed in each of the memory cells 221 (memory cells 231). Further, for example, the memory cells 221 (memory cells 231) of the memory cell array 40 may be divided into regions such as 2×2 or 2×3, and different wirings BGL may be provided for each of the regions to change the regions of the respective layers of the memory device.

[0188] In addition, Fig.10 and Fig.11 in each of the memory cell arrays 40 shown, the memory cells 221 and the memory cells 231 are two-dimensionally arranged. As shown in Fig. 12A and Fig. 12B the memory cells 221 and the memory cells 231 may also be three-dimensionally arranged. In Fig. 12A the wiring BIL provided in the memory cell array 40 is substantially perpendicular to the bit line drive circuit 52. Further, in Fig. 12B the plurality of memory cell arrays 40 all overlap with the bit line drive circuit 52. In addition, Fig. 12A and Fig. 12B show the structure of the memory cell 221, and the memory cells 231 may also be three-dimensionally arranged. Although Fig. 12A and Fig. 12B show the bit line drive circuit 52 as the lower layer, the word line drive circuit 51, the row decoder 53, or a circuit formed by laminating a plurality of them may be used instead of the bit line drive circuit 52.

[0189] By configuring the memory device 200 as shown in Fig.10 and Fig.11 the circuit area can be reduced and the memory capacity can be increased.

[0190] Furthermore, Fig. 12A and Fig. 12B adopt a structure including a plurality of Fig.10 memory cell arrays 40 shown, but a structure as shown in Fig.13 may also be adopted Fig.10 and Fig.11The structure in which the storage cell arrays 40 shown overlap with each other. That is, the storage device 200 may also adopt a structure in which DOSRAM and NOSRAM overlap with each other, that is, a structure in which the storage circuits 220 and 230 are stacked on top of each other. In addition, in Fig.13 in order to clearly show this overlapping structure, the electrical connection between each of the storage cell arrays 40 and the bit line driving circuit 52 is omitted. In addition, although the bit line driving circuit 52 is shown as the lower layer in Fig.13 , a word line driving circuit 51, a row decoder 53, or a circuit formed by stacking a plurality of them selected therefrom may be used instead of the bit line driving circuit 52. In particular, by arranging circuits such as a voltage generation circuit and a precharge circuit in the lower layer, this circuit can be used in common in each operation of the storage circuit 220 and the storage circuit 230.

[0191] Note that one mode of the present invention is not limited to the circuit structure described in this embodiment and can be appropriately changed. For example, although the storage cell arrays 40 are described as applying the storage cells 221 and 231 in this embodiment, other storage cells may be used.

[0192] In addition, this embodiment can be appropriately combined with other embodiments shown in this specification.

[0193] (Embodiment 3)

[0194] In this embodiment, a structural example of an OS transistor applicable to a semiconductor device described in the above embodiment will be described.

[0195] 〈Structural Example of Semiconductor Device〉

[0196] Fig.14 The semiconductor device shown includes a transistor 300, a transistor 500, and a capacitor 600. Fig.15A is a cross-sectional view in the channel length direction of the transistor 500, Fig. 15B is a cross-sectional view in the channel width direction of the transistor 500, Fig. 15C is a cross-sectional view in the channel width direction of the transistor 300.

[0197] The transistor 500 is a transistor (OS transistor) including a metal oxide in the channel formation region. Since the off-state current of the transistor 500 is small, by using the transistor 500 as the transistor M2 of the semiconductor device, especially the storage cell 231, the first data can be retained for a long time. In other words, since the frequency of the refresh operation is low or the refresh operation is not required, the power consumption of the semiconductor device can be reduced.

[0198] The transistor 500 is disposed above the transistor 300, and the capacitor 600 is disposed above the transistor 300 and the transistor 500. Additionally, the capacitor 600 can be the capacitor CB in the memory cell 231.

[0199] The transistor 300 is disposed on the substrate 311 and includes: a conductor 316, an insulator 315, a semiconductor region 313 formed of a part of the substrate 311; and low-resistance regions 314a and 314b used as a source region and a drain region. Additionally, the transistor 300 can be applied to the transistor M3 in the above-described embodiment, for example.

[0200] As Fig. 15C shown, in the transistor 300, the conductor 316 covers the top surface and the side surfaces in the channel width direction of the semiconductor region 313 with the insulator 315 interposed therebetween. Thus, by making the transistor 300 have a Fin-type structure, the effective channel width increases, so the on-state characteristics of the transistor 300 can be improved. In addition, since the influence of the electric field of the gate electrode can be increased, the off-state characteristics of the transistor 300 can be improved.

[0201] Additionally, the transistor 300 can be a p-channel transistor or an n-channel transistor.

[0202] The channel formation region of the semiconductor region 313, the regions in the vicinity thereof, the low-resistance regions 314a and 314b used as a source region or a drain region, etc. preferably contain a semiconductor such as a silicon-based semiconductor, and more preferably contain single-crystalline silicon. In addition, materials containing Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), etc. can also be used. Silicon that applies stress to the crystal lattice, changes the lattice plane spacing, and controls the effective mass can be used. Additionally, the transistor 300 can also be a HEMT (High Electron Mobility Transistor) using GaAs and GaAlAs, etc.

[0203] In the low-resistance regions 314a and 314b, in addition to the semiconductor material applied to the semiconductor region 313, elements such as arsenic and phosphorus that impart n-type conductivity or an element such as boron that imparts p-type conductivity are also contained.

[0204] As the conductor 316 used as a gate electrode, a conductive material such as a semiconductor material such as silicon containing elements such as arsenic and phosphorus that impart n-type conductivity or an element such as boron that imparts p-type conductivity, a metal material, an alloy material, or a metal oxide material can be used.

[0205] In addition, since the material of the conductor determines the work function, the threshold voltage of the transistor can be adjusted by selecting the material of the conductor. Specifically, materials such as titanium nitride or tantalum nitride are preferably used as the conductor. In order to have both conductivity and embeddability, a laminate of metal materials such as tungsten or aluminum is preferably used as the conductor, and tungsten is particularly preferred in terms of heat resistance.

[0206] Note that Fig.14 The structure of the transistor 300 shown is just an example and is not limited to the above structure. An appropriate transistor can be used according to the circuit structure or driving method. For example, as the structure of the transistor 300, the same structure (not shown) as that of the transistor 500 using an oxide semiconductor can also be adopted. The structure of the transistor 500 will be described later.

[0207] An insulator 320, an insulator 322, an insulator 324, and an insulator 326 are sequentially stacked so as to cover the transistor 300.

[0208] As the insulator 320, the insulator 322, the insulator 324, and the insulator 326, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, and aluminum nitride can be used.

[0209] Note that in this specification, "silicon oxynitride" refers to a material in which the oxygen content is more than the nitrogen content in its composition, and "silicon nitride oxide" refers to a material in which the nitrogen content is more than the oxygen content in its composition. Note that in this specification, "aluminum oxynitride" refers to a material in which the oxygen content is more than the nitrogen content, and "aluminum nitride oxide" refers to a material in which the nitrogen content is more than the oxygen content.

[0210] The insulator 322 can also be used as a planarization film for reducing steps generated by the transistor 300 or the like provided thereunder. For example, in order to improve the flatness of the top surface of the insulator 322, its top surface can also be planarized by a planarization process such as chemical mechanical polishing (CMP).

[0211] As the insulator 324, a film having a barrier property that can prevent hydrogen or impurities from diffusing from the substrate 311 or the transistor 300 or the like into the region where the transistor 500 is provided is preferably used.

[0212] As an example of a film having a barrier property against hydrogen, for example, silicon nitride formed by CVD can be used. Here, sometimes hydrogen diffuses into semiconductor elements having an oxide semiconductor such as the transistor 500, resulting in a deterioration of the characteristics of the semiconductor element. Therefore, it is preferable to provide a film for suppressing the diffusion of hydrogen between the transistor 500 and the transistor 300. Specifically, the film for suppressing the diffusion of hydrogen is a film with a small amount of hydrogen desorption.

[0213] The amount of hydrogen desorption can be measured, for example, by thermal desorption spectroscopy (TDS). For example, in the range where the film surface temperature in TDS analysis is from 50°C to 500°C, when the desorption amount of hydrogen converted to hydrogen atoms is converted to the amount per unit area of the insulator 324, the desorption amount of hydrogen in the insulator 324 is 10×10 15 atoms / cm 2 Hereinafter, it is preferably 5×10 15 atoms / cm 2 Hereinafter, that is sufficient.

[0214] Note that the relative dielectric constant of the insulator 326 is preferably lower than that of the insulator 324. For example, the relative dielectric constant of the insulator 326 is preferably less than 4, more preferably less than 3. For example, the relative dielectric constant of the insulator 326 is preferably 0.7 times or less, more preferably 0.6 times or less, of the relative dielectric constant of the insulator 324. By using a material with a low relative dielectric constant for the interlayer film, the parasitic capacitance generated between wirings can be reduced.

[0215] In addition, conductors 328, 330, etc. connected to the capacitor 600 or the transistor 500 are embedded in the insulators 320, 322, 324, and 326. In addition, the conductors 328 and 330 have the functions of plugs or wirings. Note that sometimes the same reference numeral is used to denote a plurality of conductors having the functions of plugs or wirings. In addition, in this specification, etc., a wiring and a plug connected to the wiring may also be one component. That is, a part of the conductor is sometimes used as a wiring, and a part of the conductor is sometimes used as a plug.

[0216] As materials for each plug and wiring (conductors 328, 330, etc.), a single layer or a laminate of conductive materials such as metal materials, alloy materials, metal nitride materials, or metal oxide materials can be used. It is preferable to use high melting point materials such as tungsten or molybdenum having both heat resistance and conductivity, and tungsten is particularly preferably used. Alternatively, low resistance conductive materials such as aluminum or copper are preferably used. By using a low resistance conductive material, the wiring resistance can be reduced.

[0217] A wiring layer may also be formed on the insulator 326 and the conductor 330. For example, in Fig.14 insulators 350, 352, and 354 are sequentially stacked. In addition, a conductor 356 is formed in the insulators 350, 352, and 354. The conductor 356 has the function of a plug or a wiring connected to the transistor 300. In addition, the conductor 356 can be formed of the same material as the conductors 328 and 330.

[0218] In addition, similar to the insulator 324, the insulator 350 is preferably an insulator that has a hydrogen barrier property, for example. Further, the conductor 356 preferably includes a conductor that has a hydrogen barrier property. In particular, a conductor that has a hydrogen barrier property is formed in an opening of the insulator 350 that has a hydrogen barrier property. By adopting this structure, the transistor 300 can be separated from the transistor 500 by a barrier layer, and thus hydrogen diffusion from the transistor 300 into the transistor 500 can be suppressed.

[0219] Note that, as the conductor that has a hydrogen barrier property, tantalum nitride or the like is preferably used, for example. Further, by laminating tantalum nitride and highly conductive tungsten, not only can the conductivity as a wiring be maintained, but also hydrogen diffusion from the transistor 300 can be suppressed. At this time, the tantalum nitride layer that has a hydrogen barrier property is preferably in contact with the insulator 350 that has a hydrogen barrier property.

[0220] In addition, a wiring layer may be formed on the insulator 354 and the conductor 356. For example, in Fig.14 , an insulator 360, an insulator 362, and an insulator 364 are laminated in sequence. Further, a conductor 366 is formed in the insulator 360, the insulator 362, and the insulator 364. The conductor 366 has a function of a plug or a wiring. In addition, the conductor 366 can be formed using the same material as the conductor 328 and the conductor 330.

[0221] In addition, similar to the insulator 324, the insulator 360 is preferably an insulator that has a hydrogen barrier property, for example. Further, the conductor 366 preferably includes a conductor that has a hydrogen barrier property. Particularly preferably, a conductor that has a hydrogen barrier property is formed in an opening of the insulator 360 that has a hydrogen barrier property. By adopting this structure, the transistor 300 can be separated from the transistor 500 by a barrier layer, and thus hydrogen diffusion from the transistor 300 into the transistor 500 can be suppressed.

[0222] In addition, a wiring layer may be formed on the insulator 364 and the conductor 366. For example, in Fig.14 , an insulator 370, an insulator 372, and an insulator 374 are laminated in sequence. Further, a conductor 376 is formed in the insulator 370, the insulator 372, and the insulator 374. The conductor 376 has a function of a plug or a wiring. In addition, the conductor 376 can be formed using the same material as the conductor 328 and the conductor 330.

[0223] In addition, similar to the insulator 324, the insulator 370 preferably uses, for example, an insulator that has a barrier property against hydrogen. Further, the conductor 376 preferably includes a conductor that has a barrier property against hydrogen. It is particularly preferable to form a conductor having a barrier property against hydrogen in the opening of the insulator 370 having a barrier property against hydrogen. By adopting this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and thus the diffusion of hydrogen from the transistor 300 into the transistor 500 can be suppressed.

[0224] In addition, a wiring layer may be formed on the insulator 374 and the conductor 376. For example, in Fig.14 , an insulator 380, an insulator 382, and an insulator 384 are sequentially stacked. Further, a conductor 386 is formed in the insulator 380, the insulator 382, and the insulator 384. The conductor 386 has a function of a plug or a wiring. In addition, the conductor 386 may be formed using the same material as the conductor 328 and the conductor 330.

[0225] In addition, similar to the insulator 324, the insulator 380 preferably uses, for example, an insulator that has a barrier property against hydrogen. Further, the conductor 386 preferably includes a conductor that has a barrier property against hydrogen. It is particularly preferable to form a conductor having a barrier property against hydrogen in the opening of the insulator 380 having a barrier property against hydrogen. By adopting this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and thus the diffusion of hydrogen from the transistor 300 into the transistor 500 can be suppressed.

[0226] The wiring layer including the conductor 356, the wiring layer including the conductor 366, the wiring layer including the conductor 376, and the wiring layer including the conductor 386 have been described above, but the semiconductor device of the present embodiment is not limited thereto. The wiring layer similar to the wiring layer including the conductor 356 may be three layers or less, and the wiring layer similar to the wiring layer including the conductor 356 may be five layers or more.

[0227] An insulator 510, an insulator 512, an insulator 514, and an insulator 516 are sequentially stacked on the insulator 384. As one of the insulator 510, the insulator 512, the insulator 514, and the insulator 516, a substance having a barrier property against oxygen or hydrogen is preferably used.

[0228] For example, as the insulator 510 and the insulator 514, a barrier film that can prevent the diffusion of hydrogen or impurities from the substrate 311 or the region where the transistor 300 is provided into the region where the transistor 500 is provided is preferably used. Therefore, the insulator 510 and the insulator 514 may be formed using the same material as the insulator 324.

[0229] As an example of a film having hydrogen barrier properties, silicon nitride formed by CVD method can be used. Here, hydrogen sometimes diffuses into semiconductor elements such as transistor 500 having an oxide semiconductor, resulting in deterioration of the characteristics of the semiconductor element. Therefore, it is preferable to provide a film that suppresses the diffusion of hydrogen between transistor 300 and transistor 500. Specifically, the film that suppresses the diffusion of hydrogen is a film with a small amount of hydrogen desorption.

[0230] For example, as the film having hydrogen barrier properties, insulator 510 and insulator 514 preferably use metal oxides such as alumina, hafnium oxide, and tantalum oxide.

[0231] In particular, alumina has a high barrier effect that does not allow oxygen and impurities such as hydrogen and moisture that cause changes in the electrical characteristics of the transistor to pass through. Therefore, during and after the manufacturing process of the transistor, alumina can prevent impurities such as hydrogen and moisture from entering transistor 500. In addition, alumina can suppress the release of oxygen from the oxide constituting transistor 500. Therefore, alumina is suitable for use as a protective film for transistor 500.

[0232] For example, as insulator 512 and insulator 516, the same materials as insulator 320 can be used. In addition, by using a material with a relatively low relative permittivity as the above insulator, the parasitic capacitance generated between the wirings can be reduced. For example, as insulator 512 and insulator 516, a silicon oxide film and a silicon oxynitride film can be used.

[0233] In addition, for example, conductor 518, a conductor constituting transistor 500 (for example, conductor 503), etc. are buried in insulator 510, insulator 512, insulator 514, and insulator 516. In addition, conductor 518 is used as a plug or wiring connected to capacitor 600 or transistor 300. Conductor 518 can be formed using the same materials as conductor 328 and conductor 330.

[0234] In particular, conductor 518 in the region in contact with insulator 510 and insulator 514 is preferably a conductor having barrier properties against oxygen, hydrogen, and water. By adopting this structure, transistor 300 and transistor 500 can be separated by a layer having barrier properties against oxygen, hydrogen, and water, thereby suppressing the diffusion of hydrogen from transistor 300 to transistor 500.

[0235] Transistor 500 is provided above insulator 516.

[0236] As Fig.15A and Fig. 15BAs shown, the transistor 500 includes: a conductor 503 embedded in insulators 514 and 516; an insulator 520 disposed on the insulator 516 and the conductor 503; an insulator 522 disposed on the insulator 520; an insulator 524 disposed on the insulator 522; an oxide 530a disposed on the insulator 524; an oxide 530b disposed on the oxide 530a; conductors 542a and 542b disposed on the oxide 530b and spaced apart from each other; an insulator 580 disposed on the conductors 542a and 542b and having an opening overlapping between the conductors 542a and 542b formed therein; an oxide 530c disposed on the bottom and side surfaces of the opening; an insulator 550 disposed on the formation surface of the oxide 530c; and a conductor 560 disposed on the formation surface of the insulator 550.

[0237] In addition, as Fig.15A and Fig. 15B shown, an insulator 544 is preferably disposed between the oxides 530a, 530b, the conductors 542a and 542b, and the insulator 580. Furthermore, as Fig.15A and Fig. 15B shown, the conductor 560 preferably includes a conductor 560a disposed inside the insulator 550 and a conductor 560b embedded inside the conductor 560a. Moreover, as Fig.15A and Fig. 15B shown, an insulator 574 is preferably disposed on the insulator 580, the conductor 560, and the insulator 550.

[0238] Note that hereinafter, the oxides 530a, 530b, and 530c are sometimes collectively referred to as the oxide 530.

[0239] In the transistor 500, three layers of the oxides 530a, 530b, and 530c are stacked in the region where the channel is formed and in its vicinity, but the present invention is not limited thereto. For example, a single layer of the oxide 530b, a two-layer structure of the oxide 530b and the oxide 530a, a two-layer structure of the oxide 530b and the oxide 530c, or a stacked structure of four or more layers may be provided. Additionally, in the transistor 500, the conductor 560 has a two-layer structure, but the present invention is not limited thereto. For example, the conductor 560 may also have a single-layer structure or a stacked structure of three or more layers. Note that Fig.14 、 Fig.15A and Fig. 15B the structure of the transistor 500 shown is merely an example and is not limited to the above structure, and an appropriate transistor may be used according to the circuit structure or the driving method.

[0240] Here, the conductor 560 is used as the gate electrode of the transistor, and the conductors 542a and 542b are used as the source electrode or the drain electrode. As described above, the conductor 560 is filled in the opening of the insulator 580 and in the region between the conductors 542a and 542b. The arrangement of the conductor 560, the conductors 542a, and the conductors 542b with respect to the opening of the insulator 580 is selected to be self-aligned. In other words, in the transistor 500, the gate electrode can be arranged self-aligned between the source electrode and the drain electrode. Thus, the conductor 560 can be formed in a manner that does not provide room for alignment, so that the occupied area of the transistor 500 can be reduced. Thus, miniaturization and high integration of the semiconductor device can be achieved.

[0241] Furthermore, since the conductor 560 is formed self-aligned in the region between the conductors 542a and 542b, the conductor 560 does not include a region overlapping with the conductors 542a and 542b. Thus, the parasitic capacitance formed between the conductor 560 and the conductors 542a and 542b can be reduced. Therefore, the switching speed of the transistor 500 can be increased, and thus the transistor 500 can have high-frequency characteristics.

[0242] The conductor 560 is sometimes used as the first gate (also referred to as the top gate) electrode. The conductor 503 is sometimes used as the second gate (also referred to as the bottom gate) electrode. In this case, by independently changing the potential supplied to the conductor 503 without linking it to the potential supplied to the conductor 560, the threshold voltage of the transistor 500 can be controlled. In particular, by supplying a negative potential to the conductor 503, the threshold voltage of the transistor 500 can be made greater than 0V and the off-state current can be reduced. Therefore, compared with the case where no negative potential is applied to the conductor 503, the drain current when the potential supplied to the conductor 560 is 0V can be reduced in the case where a negative potential is applied to the conductor 503.

[0243] The conductor 503 is arranged to overlap with the oxide 530 and the conductor 560. Thus, in the case where potentials are supplied to the conductor 560 and the conductor 503, the electric field generated from the conductor 560 and the electric field generated from the conductor 503 are connected, and the channel formation region formed in the oxide 530 can be covered. In this specification and the like, the structure of the transistor in which the channel formation region is electrically surrounded by the electric field of the first gate electrode and the electric field of the second gate electrode is referred to as a surrounded channel (S-channel) structure.

[0244] In addition, the conductor 503 has the same structure as the conductor 518, and the conductor 503a is formed in contact with the inner walls of the openings of the insulators 514 and 516, and the conductor 503b is formed inside thereof.

[0245] Insulators 520, 522, 524, and 550 are used as gate insulating films.

[0246] Here, insulator 524 in contact with oxide 530 preferably uses an insulator containing oxygen in excess of the stoichiometric composition. In other words, it is preferable to form an excess oxygen region in insulator 524. By disposing the above-mentioned insulator containing excess oxygen in contact with oxide 530, oxygen defects in oxide 530 can be reduced, thereby improving the reliability of transistor 500.

[0247] Specifically, as the insulator having an excess oxygen region, an oxide material in which a part of oxygen is desorbed by heating is preferably used. The oxide in which oxygen is desorbed by heating means that the desorption amount of oxygen converted into oxygen atoms in TDS (Thermal Desorption Spectroscopy) analysis is 1.0×10 18 atoms / cm 3 or more, preferably 1.0×10 19 atoms / cm 3 or more, more preferably 2.0×10 19 atoms / cm 3 or more, or 3.0×10 20 atoms / cm 3 or more of the oxide film. In addition, the surface temperature of the film during the above TDS analysis is preferably in the range of 100°C or higher and 700°C or lower, or 100°C or higher and 400°C or lower.

[0248] When insulator 524 has an excess oxygen region, insulator 522 preferably has a function of suppressing the diffusion of oxygen (e.g., oxygen atoms, oxygen molecules, etc.) (it is not easy for the above-mentioned oxygen to permeate).

[0249] When insulator 522 has a function of suppressing the diffusion of oxygen or impurities, the oxygen contained in oxide 530 does not diffuse to the side of insulator 520, so it is preferable. In addition, it is possible to suppress the reaction of conductor 503 with the oxygen contained in insulator 524 or oxide 530.

[0250] As the insulator 522, for example, it is preferable to use a single layer or a laminate of insulators containing so-called high-k materials such as alumina, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST). When miniaturizing and highly integrating transistors, problems such as leakage current sometimes occur due to the thinning of the gate insulating film. By using a high-k material as the insulator used as the gate insulating film, the gate potential during transistor operation can be reduced while maintaining the physical thickness.

[0251] In particular, it is preferable to use an insulator containing an oxide of one or both of aluminum and hafnium as an insulating material having a function of suppressing the diffusion of impurities and oxygen, etc. (not easily allowing the above-mentioned oxygen to pass through). As the insulator containing an oxide of one or both of aluminum and hafnium, it is preferable to use alumina, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), etc. When using such a material to form the insulator 522, the insulator 522 is used as a layer that suppresses the release of oxygen from the oxide 530 or the entry of impurities such as hydrogen from the peripheral part of the transistor 500 into the oxide 530.

[0252] Alternatively, for example, alumina, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide can also be added to the above-mentioned insulator. In addition, the above-mentioned insulator can be nitrided. Silicon oxide, silicon oxynitride, or silicon nitride can also be laminated on the above-mentioned insulator.

[0253] The insulator 520 preferably has thermal stability. For example, since silicon oxide and silicon oxynitride have thermal stability, they are preferable. In addition, by combining the insulator of the high-k material with silicon oxide or silicon oxynitride, an insulator 520 having a laminated structure with thermal stability and a high relative dielectric constant can be formed.

[0254] In addition, the insulator 520, the insulator 522, and the insulator 524 can also adopt a laminated structure of two or more layers. In this case, it is not limited to a laminated structure composed of the same material, and it can also be a laminated structure formed of different materials.

[0255] In the transistor 500, it is preferable to use a metal oxide to be used as an oxide semiconductor for the oxide 530 including a channel formation region. For example, as the oxide 530, it is preferable to use a metal oxide such as an In-M-Zn oxide (element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, etc.). In particular, the In-M-Zn oxide that can be applied to the oxide 530 is preferably the CAAC-OS or CAC-OS described in Embodiment 4. In addition, as the oxide 530, an In-Ga oxide or an In-Zn oxide can also be used.

[0256] As the metal oxide used as the channel formation region in the oxide 530, it is preferable to use a metal oxide having a band gap of 2 eV or more, preferably 2.5 eV or more. Thus, by using a metal oxide having a wider band gap, the off-state current of the transistor can be reduced.

[0257] In the oxide 530, when the oxide 530a is provided under the oxide 530b, impurities can be prevented from diffusing from the structure formed under the oxide 530a to the oxide 530b. When the oxide 530c is provided above the oxide 530b, impurities can be prevented from diffusing from the structure formed above the oxide 530c to the oxide 530b.

[0258] In addition, the oxide 530 preferably has a stacked structure of oxides having different atomic number ratios of each metal atom. Specifically, the atomic number ratio of the element M in the constituent elements of the metal oxide for the oxide 530a is preferably greater than the atomic number ratio of the element M in the constituent elements of the metal oxide for the oxide 530b. In addition, the atomic number ratio of the element M relative to In in the metal oxide for the oxide 530a is preferably greater than the atomic number ratio of the element M relative to In in the metal oxide for the oxide 530b. In addition, the atomic number ratio of In relative to the element M in the metal oxide for the oxide 530b is preferably greater than the atomic number ratio of In relative to the element M in the metal oxide for the oxide 530a. In addition, as the oxide 530c, a metal oxide that can be used for the oxide 530a or the oxide 530b can be used.

[0259] Preferably, the energy of the conduction band bottom of the oxide 530a and the oxide 530c is higher than the energy of the conduction band bottom of the oxide 530b. In other words, the electron affinity of the oxide 530a and the oxide 530c is preferably smaller than the electron affinity of the oxide 530b.

[0260] Here, at the junction of oxide 530a, oxide 530b, and oxide 530c, the energy level of the bottom of the conduction band changes smoothly. In other words, the above situation can also be expressed as the energy level of the bottom of the conduction band at the junction of oxide 530a, oxide 530b, and oxide 530c changing continuously or being continuously joined. For this purpose, it is preferable to reduce the density of defect states in the mixed layer formed at the interface between oxide 530a and oxide 530b and at the interface between oxide 530b and oxide 530c.

[0261] Specifically, by making oxide 530a and oxide 530b, and oxide 530b and oxide 530c contain a common element (as the main component) in addition to oxygen, a mixed layer with a low density of defect states can be formed. For example, when oxide 530b is an In-Ga-Zn oxide, it is preferable to use an In-Ga-Zn oxide, a Ga-Zn oxide, gallium oxide, etc. as oxide 530a and oxide 530c.

[0262] At this time, the main path of carriers is oxide 530b. By making oxide 530a and oxide 530c have the above structure, the density of defect states at the interface between oxide 530a and oxide 530b and at the interface between oxide 530b and oxide 530c can be reduced. Therefore, the influence of interface scattering on carrier conduction is reduced, and the on-state current of transistor 500 can be increased.

[0263] On oxide 530b, conductors 542a and 542b used as source electrodes and drain electrodes are provided. As conductors 542a and 542b, it is preferable to use metal elements selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum, alloys composed of the above metal elements, or alloys combining the above metal elements, etc. For example, it is preferable to use tantalum nitride, titanium nitride, tungsten nitride, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel, etc. In addition, tantalum nitride, titanium nitride, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel are conductive materials that are not easily oxidized or materials that maintain conductivity even when absorbing oxygen, so they are preferable.

[0264] In addition, as Fig.15AAs shown, sometimes regions 543a and 543b are formed as low-resistance regions at and near the interface between the oxide 530 and the conductor 542a (conductor 542b). At this time, region 543a is used as one of the source region and the drain region, and region 543b is used as the other of the source region and the drain region. In addition, a channel formation region is formed in the region sandwiched between region 543a and region 543b.

[0265] By forming the above-mentioned conductor 542a (conductor 542b) in contact with the oxide 530, the oxygen concentration in region 543a (region 543b) sometimes decreases. In addition, a metal compound layer including the metal contained in the conductor 542a (conductor 542b) and the components of the oxide 530 is sometimes formed in region 543a (region 543b). In this case, the carrier concentration in region 543a (region 543b) increases, and region 543a (region 543b) becomes a low-resistance region.

[0266] The insulator 544 is provided so as to cover the conductor 542a and the conductor 542b, suppressing the oxidation of the conductor 542a and the conductor 542b. At this time, the insulator 544 can also be provided so as to cover the side surface of the oxide 530 and contact the insulator 524.

[0267] As the insulator 544, a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, neodymium, lanthanum, magnesium, etc. can be used.

[0268] In particular, as the insulator 544, it is preferable to use alumina, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), etc., which are insulators as oxides containing one or both of aluminum and hafnium. In particular, the heat resistance of hafnium aluminate is higher than that of the hafnium oxide film. Therefore, it is not easily crystallized during the heat treatment in the subsequent process, so it is preferable. In addition, when the conductor 542a and the conductor 542b are materials with oxidation resistance or materials whose conductivity does not decrease significantly even when oxygen is absorbed, it is not necessary to provide the insulator 544. It can be appropriately designed according to the required transistor characteristics.

[0269] In addition, the insulator 550 is used as a gate insulating film. The insulator 550 is preferably arranged in contact with the inner side (upper surface and side surface) of the oxide 530c. Similar to the above-mentioned insulator 524, the insulator 550 is preferably formed using an insulator containing excessive oxygen and releasing oxygen by heating.

[0270] Specifically, silicon oxide containing excess oxygen, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide added with fluorine, silicon oxide added with carbon, silicon oxide added with carbon and nitrogen, and silicon oxide having pores can be used. In particular, silicon oxide and silicon oxynitride have thermal stability, so they are preferred.

[0271] By providing an insulator that releases oxygen upon heating in contact with the top surface of the oxide 530c as the insulator 550, oxygen can be effectively supplied from the insulator 550 to the channel formation region of the oxide 530b through the oxide 530c. In addition, similar to the insulator 524, it is preferable to reduce the concentration of impurities such as water or hydrogen in the insulator 550. The thickness of the insulator 550 is preferably 1 nm or more and 20 nm or less.

[0272] In addition, in order to efficiently supply the excess oxygen contained in the insulator 550 to the oxide 530, a metal oxide may be provided between the insulator 550 and the conductor 560. This metal oxide preferably inhibits the diffusion of oxygen from the insulator 550 to the conductor 560. By providing a metal oxide that inhibits the diffusion of oxygen, the diffusion of excess oxygen from the insulator 550 to the conductor 560 is inhibited. In other words, a reduction in the excess oxygen supplied to the oxide 530 can be inhibited. In addition, oxidation of the conductor 560 due to excess oxygen can be inhibited. As this metal oxide, a material that can be used for the insulator 544 can be used.

[0273] In Fig.15A and Fig. 15B the conductor 560 used as the first gate electrode has a two-layer structure, but it may also have a single-layer structure or a stacked structure of three or more layers.

[0274] As the conductor 560a, a conductive material having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N2O, NO, NO2, etc.), and copper atoms is preferably used. In addition, a conductive material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms and oxygen molecules) is preferably used. By making the conductor 560a have a function of suppressing the diffusion of oxygen, a decrease in conductivity due to oxidation of the conductor 560b by the oxygen contained in the insulator 550 can be inhibited. As a conductive material having a function of suppressing the diffusion of oxygen, for example, tantalum, tantalum nitride, ruthenium, or ruthenium oxide is preferably used.

[0275] As the conductor 560b, a conductive material mainly composed of tungsten, copper, or aluminum is preferably used. Since the conductor 560b is also used as a wiring, a conductor having high conductivity is preferably used. The conductor 560b may also have a stacked structure. For example, a stacked structure of titanium, titanium nitride, and the above conductive material may be adopted.

[0276] The insulator 580 is preferably disposed on the conductors 542a and 542b with the insulator 544 therebetween. The insulator 580 preferably has an excess oxygen region. For example, the insulator 580 preferably includes silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide with fluorine added, silicon oxide with carbon added, silicon oxide with carbon and nitrogen added, silicon oxide with pores, or resin, etc. In particular, silicon oxide and silicon oxynitride are preferred because they have thermal stability. In particular, silicon oxide and silicon oxide with pores are preferred because they are likely to form an excess oxygen region in subsequent processes.

[0277] By disposing the insulator 580 having an excess oxygen region in contact with the oxide 530c and releasing oxygen upon heating, the oxygen in the insulator 580 can be efficiently supplied to the oxides 530a and 530b through the oxide 530c. In addition, it is preferable to reduce the concentration of impurities such as water or hydrogen in the insulator 580.

[0278] The opening of the insulator 580 is formed so as to overlap with the region between the conductors 542a and 542b. Thereby, the conductor 560 is filled in the opening of the insulator 580 and the region sandwiched between the conductors 542a and 542b.

[0279] When miniaturizing a semiconductor device, it is necessary to shorten the gate length, but it is necessary to prevent a decrease in the conductivity of the conductor 560. For this purpose, when increasing the thickness of the conductor 560, the conductor 560 may have a shape with a high aspect ratio. In the present embodiment, since the conductor 560 is filled in the opening of the insulator 580, even if the conductor 560 has a shape with a high aspect ratio, the conductor 560 does not collapse during the process.

[0280] The insulator 574 is preferably disposed flush with the top surface of the insulator 580, the top surface of the conductor 560, and the top surface of the insulator 550. By forming the insulator 574 by sputtering, an excess oxygen region can be formed in the insulators 550 and 580. Thereby, oxygen can be supplied from this excess oxygen region to the oxide 530.

[0281] For example, as the insulator 574, a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, and magnesium can be used.

[0282] In particular, alumina has high barrier properties, and even for a thin film of 0.5 nm or more and 3.0 nm or less, it can suppress the diffusion of hydrogen and nitrogen. Thus, alumina formed by sputtering can function as an oxygen supply source while also serving as a barrier film for impurities such as hydrogen.

[0283] In addition, an insulator 581 used as an interlayer film is preferably provided on the insulator 574. Similar to the insulator 524 and the like, it is preferable to reduce the concentration of impurities such as water or hydrogen in the insulator 581.

[0284] In addition, conductors 540a and 540b are disposed in openings formed in the insulator 581, the insulator 574, the insulator 580, and the insulator 544. The conductors 540a and 540b are arranged to face each other with the conductor 560 therebetween. The conductors 540a and 540b have the same structure as the conductors 546 and 548 described later.

[0285] An insulator 582 is provided on the insulator 581. The insulator 582 preferably uses a material having oxygen or hydrogen barrier properties. Therefore, the same material as the insulator 514 can be used as the insulator 582. For example, metal oxides such as alumina, hafnium oxide, and tantalum oxide are preferably used as the insulator 582.

[0286] In particular, alumina has a high barrier effect that does not allow oxygen and impurities such as hydrogen and moisture that cause changes in the electrical characteristics of the transistor to pass through. Therefore, during and after the manufacturing process of the transistor, alumina can prevent impurities such as hydrogen and moisture from entering the transistor 500. In addition, alumina can suppress the release of oxygen from the oxides constituting the transistor 500. Therefore, alumina is suitable for use as a protective film for the transistor 500.

[0287] In addition, an insulator 586 is provided on the insulator 582. The same material as the insulator 320 can be used as the insulator 586. In addition, by using a material with a relatively low relative dielectric constant for the above insulator, the parasitic capacitance generated between the wirings can be reduced. For example, as the insulator 586, a silicon oxide film, a silicon oxynitride film, or the like can be used.

[0288] In addition, conductors 546, 548, etc. are embedded in the insulator 520, the insulator 522, the insulator 524, the insulator 544, the insulator 580, the insulator 574, the insulator 581, the insulator 582, and the insulator 586.

[0289] The conductors 546 and 548 are used as plugs or wirings connected to the capacitor 600, the transistor 500, or the transistor 300. The conductors 546 and 548 can be formed using the same materials as the conductors 328 and 330.

[0290] Next, a capacitor 600 is provided above the transistor 500. The capacitor 600 includes a conductor 610, a conductor 620, and an insulator 630.

[0291] In addition, a conductor 612 may be provided on the conductors 546 and 548. The conductor 612 is used as a plug or wiring connected to the transistor 500. The conductor 610 is used as an electrode of the capacitor 600. In addition, the conductor 612 and the conductor 610 may be formed simultaneously.

[0292] As the conductor 612 and the conductor 610, a metal film containing an element selected from molybdenum, titanium, tantalum, tungsten, aluminum, copper, chromium, neodymium, and scandium or a metal nitride film (tantalum nitride film, titanium nitride film, molybdenum nitride film, tungsten nitride film) containing the above elements as components may be used. Alternatively, conductive materials such as indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, and indium tin oxide added with silicon oxide may be used.

[0293] In Fig.14 the conductor 612 and the conductor 610 have a single-layer structure, but are not limited thereto, and may also have a stacked structure of two or more layers. For example, a conductor having high tightness with a barrier conductor and a highly conductive conductor may be formed between a barrier conductor and a highly conductive conductor.

[0294] The conductor 620 is provided so as to overlap the conductor 610 with the insulator 630 interposed therebetween. As the conductor 620, conductive materials such as a metal material, an alloy material, and a metal oxide material may be used. Tungsten or molybdenum, which has both heat resistance and conductivity, is preferably used, and tungsten is particularly preferably used. When the conductor 620 is formed simultaneously with other constituent elements such as a conductor, Cu (copper) or Al (aluminum), which is a low-resistance metal material, may be used.

[0295] An insulator 650 is provided on the conductor 620 and the insulator 630. The insulator 650 may be formed of the same material as the insulator 320. In addition, the insulator 650 may be used as a planarization film covering the uneven shape thereunder.

[0296] By adopting this structure, it is possible to improve the reliability while suppressing the change in the electrical characteristics of a semiconductor device using a transistor including an oxide semiconductor. In addition, miniaturization or high integration of a semiconductor device using a transistor including an oxide semiconductor can be achieved.

[0297] <Examples of the structure of the transistor>

[0298] Note that the structure of the transistor 500 of the semiconductor device shown in this embodiment is not limited to the above structure. Hereinafter, examples of the structure applicable to the transistor 500 will be described. Note that the transistors described below are modified examples of the transistors described above. Therefore, in the following description, the differences will be mainly described, and the same parts may sometimes be omitted.

[0299] 〈〈Example 1 of Transistor Structure〉〉

[0300] Refer to Fig.16A 、 Fig. 16B and Fig. 16C to describe an example of the structure of the transistor 500A. Fig.16A is a top view of the transistor 500A. Fig. 16B is Fig.16A a cross-sectional view of the portion indicated by the dotted line L1 - L2 in Fig. 16C is Fig.16A a cross-sectional view of the portion indicated by the dotted line W1 - W2 in Fig.16A In the top view of

[0301] In Fig.16A 、 Fig. 16B and Fig. 16C the transistor 500A, insulators 511, 512, 514, 516, 580, 574, and 581 used as interlayer films are shown. In addition, Fig.16A 、 Fig. 16B and Fig. 16C show conductors 540a, 540b, and 505 electrically connected to the transistor 500A. In particular, the conductors 540a and 540b are used as contact plugs, and the conductor 505 is used as a wiring.

[0302] The transistor 500A includes: conductors 560 (conductors 560a and 560b) used as the first gate electrode; conductors 503 (conductors 503a and 503b) used as the second gate electrode; insulator 550 used as the first gate insulating film; insulators 520, 522, 524 used as the second gate insulating film; oxide 530 (oxides 530a, 530b, and 530c) including the region where the channel is formed; conductor 542a used as one of the source and drain; conductor 542b used as the other of the source and drain; insulator 544.

[0303] In addition, in Fig.16A 、 Fig. 16B and Fig. 16CIn the transistor 500A shown, an oxide 530c, an insulator 550, and a conductor 560 are arranged in an opening provided in an insulator 580 with an insulator 544 interposed therebetween. Further, the oxide 530c, the insulator 550, and the conductor 560 are arranged between a conductor 542a and a conductor 542b.

[0304] The insulators 511 and 512 are used as interlayer films.

[0305] As the interlayer film, a single layer or a stack of insulators such as silicon oxide, silicon oxynitride, silicon nitride oxide, aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST) can be used. Alternatively, for example, alumina, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide can be added to these insulators. Further, these insulators can be nitrided. Also, a silicon oxide, silicon oxynitride, or silicon nitride layer can be stacked on the above insulators.

[0306] For example, the insulator 511 is preferably used as a barrier film that suppresses the entry of impurities such as water or hydrogen from the substrate side into the transistor 500A. Therefore, as the insulator 511, an insulating material having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms (not easily allowing the above impurities to pass through) is preferably used. In addition, an insulating material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms and oxygen molecules) (not easily allowing the above oxygen to pass through) is preferably used. Further, for example, alumina or silicon nitride is preferably used as the insulator 511. By adopting this structure, the diffusion of impurities such as hydrogen and water from the side closer to the substrate than the insulator 511 to the transistor 500A side can be suppressed.

[0307] For example, the relative permittivity of the insulator 512 is preferably lower than that of the insulator 511. By using a material with a low relative permittivity for the interlayer film, the parasitic capacitance generated between wirings can be reduced.

[0308] The conductor 505 is formed in a manner embedded in the insulator 512. Here, the height of the top surface of the conductor 505 and the height of the top surface of the insulator 512 can be substantially the same. The conductor 505 has a single-layer structure, but the present invention is not limited thereto. For example, the conductor 505 can also have a multilayer film structure of two or more layers. As the conductor 505, a highly conductive material mainly composed of tungsten, copper, or aluminum is preferably used.

[0309] In transistor 500A, the conductor 560 is sometimes used as the first gate (also referred to as the top gate) electrode. In addition, the conductor 503 is sometimes used as the second gate (also referred to as the bottom gate) electrode. In this case, by independently changing the potential supplied to the conductor 503 without linking it to the potential supplied to the conductor 560, the threshold voltage of the transistor 500A can be controlled. In particular, by supplying a negative potential to the conductor 503, the threshold voltage of the transistor 500A can be made greater than 0V and the off-state current can be reduced. Therefore, compared with the case where no negative potential is applied to the conductor 503, the drain current when the potential applied to the conductor 560 is 0V can be reduced in the case where a negative potential is applied to the conductor 503.

[0310] In addition, for example, by overlapping the conductor 503 on the conductor 560, when potentials are supplied to the conductor 560 and the conductor 503, the electric field generated from the conductor 560 and the electric field generated from the conductor 503 are connected, and the channel formation region formed in the oxide 530 can be covered.

[0311] That is to say, the channel formation region can be electrically surrounded by the electric field of the conductor 560 used as the first gate electrode and the electric field of the conductor 503 used as the second gate electrode. In this specification, the structure of a transistor in which the channel formation region is electrically surrounded by the electric field of the first gate electrode and the electric field of the second gate electrode is referred to as a surrounded channel (S-channel) structure.

[0312] Similar to the insulators 511 and 512, the insulators 514 and 516 are used as interlayer films. For example, the insulator 514 is preferably used as a barrier film that suppresses impurities such as water or hydrogen from entering the transistor 500A from the substrate side. By adopting this structure, diffusion of impurities such as hydrogen and water from the side closer to the substrate than the insulator 514 to the transistor 500A side can be suppressed. For example, the relative dielectric constant of the insulator 516 is preferably lower than that of the insulator 514. By using a material with a low relative dielectric constant for the interlayer film, the parasitic capacitance generated between the wirings can be reduced.

[0313] In the conductor 503 used as the second gate electrode, a conductor 503a is formed in contact with the inner walls of the openings of the insulators 514 and 516, and a conductor 503b is formed inside thereof. Here, the height of the top surfaces of the conductor 503a and the conductor 503b can be substantially the same as the height of the top surface of the insulator 516. In addition, in the transistor 500A, the conductor 503a and the conductor 503b are stacked, but the present invention is not limited thereto. For example, the conductor 503 can have a single-layer structure or a stacked structure of three or more layers.

[0314] Here, as the conductor 503a, it is preferable to use a conductive material having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms (not allowing the above impurities to pass through easily). In addition, it is preferable to use a conductive material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms and oxygen molecules) (not allowing the above oxygen to pass through easily). In this specification, "the function of suppressing the diffusion of impurities or oxygen" means the function of suppressing the diffusion of any one or all of the above impurities and the above oxygen.

[0315] For example, by providing the conductor 503a with a function of suppressing the diffusion of oxygen, a decrease in conductivity due to oxidation of the conductor 503b can be suppressed.

[0316] In addition, when the conductor 503 also has a wiring function, it is preferable to use a highly conductive conductive material with tungsten, copper or aluminum as a main component as the conductor 503b. In this case, it is not necessary to provide the conductor 505. In the drawings, the conductor 503b has a single-layer structure, but it may also have a laminated structure, for example, a laminated structure of titanium, titanium nitride and the above conductive materials may be used.

[0317] The insulator 522 used as the second gate insulating film preferably has a barrier property. When the insulator 522 has a barrier property, the insulator 522 is used as a layer that suppresses impurities such as hydrogen from entering the transistor 500A from the surrounding area of ​​the transistor 500A.

[0318] Note that Fig. 16B and Fig. 16C In the embodiment, the second gate insulating film has a three-layer stacked structure, but may also have a single-layer structure, a two-layer structure, or a four-layer stacked structure. In this case, the stacked structure is not limited to a stacked structure made of the same material, but may also be a stacked structure made of different materials.

[0319] The oxide 530 including the region used as the channel formation region includes an oxide 530a, an oxide 530b on the oxide 530a, and an oxide 530c on the oxide 530b. When the oxide 530a is provided below the oxide 530b, it is possible to suppress the diffusion of impurities from the structure formed below the oxide 530a to the oxide 530b. In addition, when the oxide 530c is provided above the oxide 530b, it is possible to suppress the diffusion of impurities from the structure formed above the oxide 530c to the oxide 530b. As the oxide 530, an oxide semiconductor of one of the above-mentioned metal oxides can be used.

[0320] In addition, the insulator 530c is preferably provided in the opening provided in the insulator 580 via the oxide 530c and the insulator 544. When the insulator 544 has a barrier property, diffusion of impurities from the insulator 580 into the oxide 530 can be suppressed.

[0321] The conductor 542a used as one of the source electrode and the drain electrode and the conductor 542b used as the other of the source electrode and the drain electrode can be made of a metal such as aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, or tungsten, or an alloy containing these as main components. In particular, a metal nitride film such as a tantalum nitride film is preferred because it has a barrier property against hydrogen and oxygen and has high oxidation resistance.

[0322] In addition, although Fig. 16B Although a single-layer structure is shown in the figure, a stacked structure of two or more layers may be adopted. For example, a tantalum nitride film and a tungsten film are preferably stacked. In addition, a titanium film and an aluminum film may be stacked. In addition, a two-layer structure of stacking an aluminum film on a tungsten film, a two-layer structure of stacking a copper film on a copper-magnesium-aluminum alloy film, a two-layer structure of stacking a copper film on a titanium film, and a two-layer structure of stacking a copper film on a tungsten film may also be adopted.

[0323] Alternatively, a three-layer structure may be used in which an aluminum film or a copper film is stacked on a titanium film or a titanium nitride film and a titanium film or a titanium nitride film is formed thereon, or an aluminum film or a copper film is stacked on a molybdenum film or a molybdenum nitride film and a molybdenum film or a molybdenum nitride film is formed thereon. Alternatively, a transparent conductive material containing indium oxide, tin oxide, or zinc oxide may be used.

[0324] In addition, a barrier layer may be provided on the conductor 542a and the conductor 542b. The barrier layer is preferably made of a material that has a barrier property against oxygen or hydrogen. By adopting this structure, oxidation of the conductor 542a and the conductor 542b can be suppressed when the insulator 544 is formed.

[0325] The barrier layer may be made of, for example, a metal oxide. In particular, it is preferable to use an insulating film having barrier properties to oxygen or hydrogen, such as aluminum oxide, hafnium oxide, or gallium oxide. Alternatively, silicon nitride formed by CVD may be used.

[0326] By including the barrier layer, the range of choices of materials for the conductors 542a and 542b can be expanded. For example, the conductors 542a and 542b can be made of materials with low oxidation resistance and high conductivity, such as tungsten or aluminum. In addition, for example, a conductor that is easy to deposit or process can be used.

[0327] The insulator 550 is used as a first gate insulating film. The insulator 550 is preferably provided in an opening provided in the insulator 580 via the oxide 530 c and the insulator 544 .

[0328] With the miniaturization and high integration of transistors, due to the thinning of the gate insulating film, problems such as leakage current sometimes occur. In this case, the insulator 550 may also have the same laminated structure as the second insulating film. By making the insulator used as the gate insulating film have a laminated structure of a high-k material and a material with thermal stability, the gate potential during transistor operation can be reduced while maintaining the physical thickness. In addition, a laminated structure with thermal stability and a high relative dielectric constant can be achieved.

[0329] The conductor 560 used as the first gate electrode includes a conductor 560a and a conductor 560b on the conductor 560a. Similar to the conductor 503a, it is preferable to use a conductive material for the conductor 560a that has the function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms. In addition, it is preferable to use a conductive material that has the function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.).

[0330] When the conductor 560a has the function of suppressing the diffusion of oxygen, the selectivity of the material of the conductor 560b can be improved. That is to say, by including the conductor 560a, the oxidation of the conductor 560b can be suppressed, and a decrease in conductivity can be prevented.

[0331] As the conductive material having the function of suppressing oxygen diffusion, it is preferable to use tantalum, tantalum nitride, titanium nitride, ruthenium, or ruthenium oxide, etc. In addition, as the conductor 560a, an oxide semiconductor that can be used for the oxide 530 can be used. In this case, by forming the conductor 560b using a sputtering method, the resistance value of the conductor 560a can be reduced to make it a conductive layer. It can be called an OC (Oxide Conductor) electrode.

[0332] As the conductor 560b, it is preferable to use a conductive material mainly composed of tungsten, copper, or aluminum. In addition, since the conductor 560 is used as a wiring, it is preferable to use a conductor with high conductivity. In addition, the conductor 560b may also have a laminated structure. For example, a laminate of titanium, titanium nitride, and the above-mentioned conductive material can be adopted.

[0333] An insulator 544 is disposed between the insulator 580 and the transistor 500A. As the insulator 544, it is preferable to use an insulating material that has the function of suppressing the diffusion of impurities such as water or hydrogen and oxygen. For example, it is preferably alumina or hafnium oxide, etc. In addition, for example, metal oxides such as magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, or tantalum oxide, silicon oxynitride, or silicon nitride, etc. can also be used.

[0334] By including the insulator 544, it is possible to suppress impurities such as water and hydrogen contained in the insulator 580 from diffusing through the oxide 530c and the insulator 550 into the oxide 530b. In addition, it is possible to suppress the oxidation of the conductor 560 by the excess oxygen contained in the insulator 580.

[0335] The insulator 580, the insulator 574, and the insulator 581 are used as interlayer films.

[0336] Similar to the insulator 514, the insulator 574 is preferably used as a barrier insulating film that suppresses the entry of impurities such as water or hydrogen from the outside into the transistor 500A.

[0337] In addition, similar to the insulator 516, the relative dielectric constants of the insulator 580 and the insulator 581 are preferably lower than that of the insulator 574. By using a material with a low relative dielectric constant for the interlayer film, the parasitic capacitance generated between the wirings can be reduced.

[0338] Furthermore, the transistor 500A can also be electrically connected to other structures through plugs or wirings such as the conductor 540a and the conductor 540b embedded in the insulator 580, the insulator 574, and the insulator 581.

[0339] In addition, similar to the conductor 503, as the materials of the conductor 540a and the conductor 540b, a single layer or a stack of conductive materials such as a metal material, an alloy material, a metal nitride material, or a metal oxide material can be used. For example, it is preferable to use a high melting point material such as tungsten or molybdenum that has both heat resistance and conductivity. Alternatively, it is preferable to use a low resistance conductive material such as aluminum or copper. By using a low resistance conductive material, the wiring resistance can be reduced.

[0340] For example, by using a stacked structure of tantalum nitride, which is a conductor having a barrier property against hydrogen and oxygen, and tungsten having high conductivity, as the conductor 540a and the conductor 540b, it is possible to suppress the diffusion of impurities from the outside while maintaining the conductivity of the wiring.

[0341] By having the above structure, it is possible to provide a semiconductor device including a transistor containing an oxide semiconductor with a large on-state current. In addition, it is possible to provide a semiconductor device including a transistor containing an oxide semiconductor with a small off-state current. In addition, it is possible to provide a semiconductor device in which electrical characteristics fluctuations are suppressed, having stable electrical characteristics, and improved reliability.

[0342] 〈〈Example of the structure of the transistor 2〉〉

[0343] Refer to Fig.17A , Fig. 17B and Fig. 17C to describe an example of the structure of the transistor 500B. Fig.17A is a top view of the transistor 500B. Fig. 17Bis the cross-sectional view of the part indicated by the dash-dotted line L1-L2 in Fig.17A . Fig. 17C is the cross-sectional view of the part indicated by the dash-dotted line W1-W2 in Fig.17A . In the top view of Fig.17A , for clarity, a part of the constituent elements is omitted.

[0344] Transistor 500B is a modified example of transistor 500A. Thus, to avoid redundant description, mainly the differences from transistor 500A will be described.

[0345] Transistor 500B includes a region where the conductor 542a (conductor 542b) overlaps with the oxide 530c, the insulator 550, and the conductor 560. By adopting this structure, a transistor with a high on-state current can be provided. In addition, a transistor with high controllability can be provided.

[0346] The conductor 560 used as the first gate electrode includes the conductor 560a and the conductor 560b on the conductor 560a. Similar to the conductor 503a, a conductive material having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms is preferably used as the conductor 560a. In addition, a conductive material having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) is preferably used.

[0347] When the conductor 560a has a function of suppressing the diffusion of oxygen, the selectivity of the material of the conductor 560b can be improved. That is, by including the conductor 560a, the oxidation of the conductor 560b can be suppressed, and the decrease in conductivity can be prevented.

[0348] In addition, the insulator 544 is provided so as to cover the top surface and the side surface of the conductor 560, the side surface of the insulator 550, and the side surface of the oxide 530c. An insulating material having a function of suppressing the diffusion of impurities such as water or hydrogen and oxygen is preferably used as the insulator 544. For example, alumina or hafnium oxide is preferably used. In addition, for example, metal oxides such as magnesia, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, or tantalum oxide, silicon oxynitride, or silicon nitride can also be used.

[0349] By providing the insulator 544, the oxidation of the conductor 560 can be suppressed. In addition, by including the insulator 544, the diffusion of impurities such as water and hydrogen contained in the insulator 580 into the transistor 500B can be suppressed.

[0350] In addition, the structure of the contact holes of transistor 500B is different from that of transistor 500A. In transistor 500B, a blocking insulator 576a (insulator 576b) is provided between the conductor 546a (conductor 546b) used as the contact hole and the insulator 580. By providing the insulator 576a (insulator 576b), it is possible to suppress the reaction of oxygen in the insulator 580 with the conductor 546, resulting in oxidation of the conductor 546.

[0351] In addition, by providing the blocking insulator 576a (insulator 576b), the range of choices for the material of the conductor for the plug or wiring can be expanded. For example, by using a metal material having the property of absorbing oxygen and high conductivity as the conductor 546a (conductor 546b), a low-power semiconductor device can be provided. Specifically, materials with low oxidation resistance and high conductivity such as tungsten or aluminum can be used. In addition, for example, a conductor that is easy to deposit or process can be used.

[0352] 〈〈Example Structure of Transistor 3〉〉

[0353] Refer to Fig.18A 、 Fig.18B and Fig.18C to describe the example structure of transistor 500C. Fig.18A is a top view of transistor 500C. Fig.18B is in Fig.18A a cross-sectional view of the portion indicated by the dashed line L1 - L2. Fig.18C is in Fig.18A a cross-sectional view of the portion indicated by the dashed line W1 - W2. In Fig.18A the top view, for clarity, a part of the components is omitted.

[0354] Transistor 500C is a modified example of transistor 500A. Therefore, to avoid redundant description, the differences from transistor 500A will be mainly described.

[0355] Fig.18A 、 Fig.18B and Fig.18CThe transistor 500C shown has a conductor 547a disposed between the conductor 542a and the oxide 530b, and a conductor 547b disposed between the conductor 542b and the oxide 530b. Here, the conductor 542a (conductor 542b) has a region that extends beyond the top surface of the conductor 547a (conductor 547b) and the side surface on the side of the conductor 560 and contacts the top surface of the oxide 530b. Here, as the conductor 547a and the conductor 547b, conductors that can be used for the conductor 542a and the conductor 542b can be used. In addition, the thickness of the conductor 547a and the conductor 547b is preferably at least thicker than that of the conductor 542a and the conductor 542b.

[0356] Since Fig.18A 、 Fig.18B and Fig.18C the transistor 500C shown has the above structure, compared with the transistor 500A, the conductor 542a and the conductor 542b can be brought closer to the conductor 560. Or, the end portions of the conductor 542a and the conductor 542b can be overlapped with the conductor 560. Thereby, the substantial channel length of the transistor 500C can be reduced, and the on-state current and frequency characteristics can be improved.

[0357] In addition, the conductor 547a (conductor 547b) is preferably overlapped with the conductor 542a (conductor 542b). By adopting this structure, when etching the opening for forming the buried conductor 540a (conductor 540b), the conductor 547a (conductor 547b) is used as an etch stop layer to prevent over-etching of the oxide 530b.

[0358] Furthermore, Fig.18A 、 Fig.18B and Fig.18C in the transistor 500C shown, the insulator 545 can also be disposed in contact with the insulator 544. The insulator 544 is preferably used as a barrier insulating film to suppress the entry of impurities such as water or hydrogen or excess oxygen into the transistor 500C from the insulator 580 side. As the insulator 545, insulators that can be used for the insulator 544 can be used. In addition, as the insulator 544, for example, nitride insulators such as aluminum nitride, titanium aluminum nitride, titanium nitride, silicon nitride, or silicon oxynitride can also be used.

[0359] In addition, in Fig.18A 、 Fig.18B and Fig.18C in the transistor 500C shown, compared with Fig.16A 、 Fig. 16B and Fig. 16CUnlike the transistor 500A shown, the conductor 503 may also have a single-layer structure. At this time, an insulating film that becomes the insulator 516 may be formed on the patterned conductor 503, and the top of this insulating film may be removed by using the CMP method or the like until the top surface of the conductor 503 is exposed. Here, it is preferable to improve the flatness of the top surface of the conductor 503. For example, the average surface roughness (Ra) of the top surface of the conductor 503 may be 1 nm or less, preferably 0.5 nm or less, and more preferably 0.3 nm or less. Thereby, the flatness of the insulating layer formed on the conductor 503 can be improved, and the crystallinity of the oxide 530b and the oxide 530c can be improved.

[0360] <<Example Structure 4 of Transistor>>

[0361] Refer to Fig.19A , Fig.19B and Fig.19C to describe the example structure of the transistor 500D. Fig.19A is a top view of the transistor 500D. Fig.19B is Fig.19A a cross-sectional view of the portion indicated by the dashed line L1-L2 in Fig.19C is Fig.19A a cross-sectional view of the portion indicated by the dashed line W1-W2 in Fig.19A In the top view of

[0362] The structure of the transistor 500D is different from that of the transistors 500A, 500B, and 500C. Therefore, to prevent repeated description, the description of the parts that overlap with the transistors 500A, 500B, and 500C is mainly omitted, and the differences from the above transistors are mainly described.

[0363] Similar to the transistor 500C shown in Fig.18A , Fig.18B and Fig.18C the transistor 500D shown in FIG. 19A to FIG. 19C uses the conductor 503 having the function of the second gate also as a wiring without providing the conductor 505. In addition, an insulator 550 is included on the oxide 530c, and a metal oxide 552 is included on the insulator 550. In addition, a conductor 560 is included on the metal oxide 552, and an insulator 570 is included on the conductor 560. In addition, an insulator 571 is included on the insulator 570.

[0364] The metal oxide 552 preferably has a function of suppressing oxygen diffusion. By providing the metal oxide 552 that suppresses oxygen diffusion between the insulator 550 and the conductor 560, the oxygen diffusion into the conductor 560 is suppressed. In other words, a decrease in the amount of oxygen supplied to the oxide 530 can be suppressed. In addition, oxidation of the conductor 560 due to oxygen can be suppressed.

[0365] In addition, the metal oxide 552 can be used as a part of the first gate. For example, an oxide semiconductor that can be used as the oxide 530 can be used as the metal oxide 552. In this case, by forming the conductor 560 using a sputtering method, the resistance value of the metal oxide 552 can be reduced to become a conductive layer. It can be referred to as an OC (Oxide Conductor) electrode.

[0366] In addition, the metal oxide 552 is sometimes used as a part of the gate insulating film. Therefore, when silicon oxide or silicon oxynitride or the like is used for the insulator 550, a metal oxide as a high-k material having a high relative dielectric constant is preferably used as the metal oxide 552. By adopting this stacked structure, a stacked structure having thermal stability and a high relative dielectric constant can be formed. Therefore, while maintaining the physical thickness, the gate potential applied during transistor operation can be reduced. In addition, the equivalent oxide thickness (EOT) of the insulating layer used as the gate insulating film can be reduced.

[0367] Although the metal oxide 552 in the transistor 500D is shown as a single-layer structure, a stacked structure of two or more layers can also be adopted. For example, a metal oxide used as a part of the gate electrode and a metal oxide layer used as a part of the gate insulating film can be stacked.

[0368] When the metal oxide 552 is used as the gate electrode, the on-state current of the transistor 500D can be increased without weakening the influence of the electric field from the conductor 560. In addition, when the metal oxide 552 is used as the gate insulating film, by maintaining the distance between the conductor 560 and the oxide 530 using the physical thicknesses of the insulator 550 and the metal oxide 552, the leakage current between the conductor 560 and the oxide 530 can be suppressed. Thus, by providing the stacked structure of the insulator 550 and the metal oxide 552, the physical distance between the conductor 560 and the oxide 530 and the electric field strength applied from the conductor 560 to the oxide 530 can be easily adjusted.

[0369] Specifically, an oxide semiconductor that can be used for the oxide 530 can be used as the metal oxide 552 by making it have a low resistance. Or, a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, etc. can be used.

[0370] In particular, it is preferable to use aluminum oxide, hafnium oxide, hafnium aluminate (hafnium aluminates) and the like, which are insulating layers containing one or both of aluminum and hafnium as oxides. In particular, hafnium aluminate has higher heat resistance than hafnium oxide film. Therefore, it is not easily crystallized during the heat treatment in the subsequent process, so it is preferable. Note that the metal oxide 552 is not an essential component and can be appropriately designed according to the required transistor characteristics.

[0371] As the insulator 570, it is preferable to use an insulating material having a function of suppressing the permeation of impurities such as water or hydrogen and oxygen. For example, it is preferable to use aluminum oxide or hafnium oxide. Thereby, oxidation of the conductor 560 due to oxygen from above the insulator 570 can be prevented. In addition, it is possible to suppress impurities such as water or hydrogen from above the insulator 570 from entering the oxide 530 through the conductor 560 and the insulator 550.

[0372] The insulator 571 is used as a hard mask. By providing the insulator 571, the conductor 560 can be processed such that the side surface of the conductor 560 is substantially perpendicular to the substrate surface. Specifically, the angle formed by the side surface of the conductor 560 and the substrate surface can be 75° or more and 100° or less, preferably 80° or more and 95° or less.

[0373] In addition, the insulator 571 can also be used as a diffusion barrier layer by using an insulating material having a function of suppressing the permeation of impurities such as water or hydrogen and oxygen as the insulator 571. In this case, the insulator 570 may not be provided.

[0374] By using the insulator 571 as a hard mask, a part of the insulator 570, the conductor 560, the metal oxide 552, the insulator 550, and the oxide 530c is selectively removed, so that their side surfaces can be made substantially coincident, and a part of the surface of the oxide 530b is exposed.

[0375] In addition, the transistor 500D has a region 531a and a region 531b on a part of the surface of the exposed oxide 530b. One of the region 531a and the region 531b is used as a source region, and the other is used as a drain region.

[0376] For example, by using ion implantation, ion doping, plasma immersion ion implantation, or plasma treatment, etc., impurity elements such as phosphorus or boron are introduced into the surface of the exposed oxide 530b, so that the region 531a and the region 531b can be formed. Note that in the present embodiment and the like, the "impurity element" refers to an element other than the main component element.

[0377] Alternatively, a metal film may be formed after a part of the surface of the oxide 530b is exposed, and then a heat treatment may be performed to diffuse the elements contained in the metal film into the oxide 530b, thereby forming the regions 531a and 531b.

[0378] The resistivity of the region in the oxide 530b into which the impurity element is introduced decreases. Thus, the regions 531a and 531b are sometimes referred to as "impurity regions" or "low-resistance regions".

[0379] By using the insulator 571 and / or the conductor 560 as a mask, the regions 531a and 531b can be formed self-aligned. Therefore, the region 531a and / or the region 531b do not overlap with the conductor 560, and the parasitic capacitance can be reduced. In addition, a bias region is not formed between the channel formation region and the source / drain region (the region 531a or the region 531b). By forming the regions 531a and 531b self-aligned, an increase in the on-state current, a decrease in the threshold voltage, an increase in the operating frequency, etc. can be achieved.

[0380] Alternatively, in order to further reduce the off-state current, a bias region may be provided between the channel formation region and the source / drain region. The bias region is a region with a high resistivity and is a region into which the above-described impurity element is not introduced. By introducing the above-described impurity element after the insulator 575 is formed, a bias region can be formed. In this case, like the insulator 571 and the like, the insulator 575 is also used as a mask. Therefore, the region of the oxide 530b that overlaps with the insulator 575 is not introduced with the impurity element, and thus the resistivity of this region can be maintained high.

[0381] The transistor 500D includes the insulator 575 on the sides of the insulator 570, the conductor 560, the metal oxide 552, the insulator 550, and the oxide 530c. The insulator 575 is preferably an insulator with a low relative dielectric constant. For example, it is preferable to use silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide added with fluorine, silicon oxide added with carbon, silicon oxide added with carbon and nitrogen, silicon oxide with voids, or resin, etc. In particular, when silicon oxide, silicon oxynitride, silicon nitride oxide, or silicon oxide with voids is used for the insulator 575, an excess oxygen region can be easily formed in the insulator 575 in a subsequent process, so it is preferable. In addition, silicon oxide and silicon oxynitride have thermal stability, so they are preferable. Furthermore, the insulator 575 preferably has a function of diffusing oxygen.

[0382] Alternatively, the transistor 500D includes the insulator 544 on the insulator 575 and the oxide 530. The insulator 544 is preferably formed by a sputtering method. By using the sputtering method, an insulator with few impurities such as water or hydrogen can be formed. For example, as the insulator 544, it is preferable to use aluminum oxide.

[0383] Sometimes, the oxide film formed by sputtering extracts hydrogen from the formed structure. Therefore, the insulator 544 extracts hydrogen and water from the oxide 530 and the insulator 575, and the hydrogen concentration of the oxide 530 and the insulator 575 can be reduced.

[0384] <<Example Structure 5 of Transistor>>

[0385] Refer to FIG. 20A to FIG. 20C to describe the example structure of the transistor 500E. Fig. 20A It is a top view of the transistor 500E. Fig. 20B It is in Fig. 20A a cross-sectional view of the part indicated by the dotted line L1 - L2. Fig. 20C It is in Fig. 20A a cross-sectional view of the part indicated by the dotted line W1 - W2. In Fig. 20A the top view, for clarity, a part of the components is omitted.

[0386] The structure of the transistor 500E is different from that of the transistors 500A, 500B, 500C, and 500D. Therefore, to prevent repeated description, the description of the parts that overlap with the transistors 500A, 500B, 500C, and 500D is omitted, and the differences from the above-mentioned transistors are mainly described.

[0387] In Fig. 20A , Fig. 20B and Fig. 20C , on a part of the surface of the exposed oxide 530b, the conductive bodies 542a and 542b are not provided, including the regions 531a and 531b. One of the regions 531a and 531b is used as a source region, and the other is used as a drain region. In addition, an insulator 573 is included between the oxide 530b and the insulator 544.

[0388] Fig. 20B The regions 531a and 531b shown are regions where the oxide 530b is added with the following elements. The regions 531a and 531b can be formed using, for example, a dummy gate.

[0389] Specifically, a dummy gate is provided on the oxide 530b, and this dummy gate is used as a mask to add an element that makes a part of the region of the oxide 530b have a low resistance to the oxide 530b. That is, this element is added to the regions of the oxide 530a and the oxide 530b that do not overlap with the dummy gate, thereby forming the regions 531a and 531b. As a method for adding this element, the following can be used: ion implantation method in which the ionized source gas is mass-separated and added; ion doping method in which the ionized source gas is not mass-separated and added; and plasma immersion ion implantation method, etc.

[0390] In addition, as an element that makes a part of the oxide 530b low in resistance, boron or phosphorus is typical. In addition, hydrogen, carbon, nitrogen, fluorine, sulfur, chlorine, titanium, rare gas, etc. can also be used. Typical examples of rare gas include helium, neon, argon, krypton, and xenon. The concentration of the element can be measured by secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry) or the like.

[0391] In particular, boron and phosphorus can be added to the equipment of the production line of Si transistors that include amorphous silicon or low-temperature polysilicon in the semiconductor layer, so that part of the oxide 530b can be made low-resistance by using the equipment of the production line. In other words, part of the production line of Si transistors can be used in the manufacturing process of the transistor 500E.

[0392] Next, an insulating film serving as an insulator 573 and an insulating film serving as an insulator 544 may be formed over the oxide 530b and the dummy gate. By providing a stack of the insulating film serving as the insulator 573 and the insulating film serving as the insulator 544, a region where the region 531a or the region 531b overlaps with the oxide 530c and the insulator 550 may be provided.

[0393] Specifically, an insulating film that becomes the insulator 580 is provided on the insulating film that becomes the insulator 544, and then the insulating film that becomes the insulator 580 is subjected to a CMP (Chemical Mechanical Polishing) process to remove a portion of the insulating film that becomes the insulator 580, thereby exposing the dummy gate. Next, when removing the dummy gate, it is preferable to also remove a portion of the insulator 573 that is in contact with the dummy gate. As a result, the insulator 544 and the insulator 573 are exposed on the side of the opening provided in the insulator 580, and a portion of the region 531a and the region 531b provided in the oxide 530b are exposed on the bottom surface of the opening. Next, an oxide film that becomes the oxide 530c, an insulating film that becomes the insulator 550, and a conductive film that becomes the conductor 560 are sequentially formed in the opening, and then a portion of the oxide film that becomes the oxide 530c, the insulating film that becomes the insulator 550, and the conductive film that becomes the conductor 560 are removed by CMP treatment or the like until the insulator 580 is exposed, thereby forming Fig. 20A , Fig. 20B and Fig. 20C The transistor shown.

[0394] Note that the insulator 573 and the insulator 544 are not necessarily provided and may be appropriately designed according to required transistor characteristics.

[0395] Fig. 20A , Fig. 20B and Fig. 20C the transistors shown do not have the conductors 542a and 542b, thereby reducing the manufacturing cost of the transistors.

[0396] <<Structural Example 6 of Transistor>>

[0397] Although in Fig.15A and Fig. 15B a structural example is shown in which the conductor 560 used as a gate is formed inside the opening of the insulator 580, a structure in which the insulator is provided above the conductor may also be employed, for example. Fig.21A , Fig. 21B , Fig.22A and Fig. 22B show structural examples of such transistors.

[0398] Fig.21A is a top view of the transistor, Fig. 21B is a perspective view of the transistor. In addition, Fig.22A shows a cross-sectional view along Fig.21A L1 - L2 in Fig. 22B shows a cross-sectional view along Fig.21A W1 - W2 in

[0399] Fig.21A , Fig. 21B , Fig.22A and Fig. 22B the transistors shown include a conductor BGE having the function of a back gate, an insulator BGI having the function of a gate insulating film, an oxide semiconductor S, an insulator FGI having the function of a gate insulating film, a conductor FGE having the function of a front gate, and a conductor WE having the function of a wiring. In addition, the conductor PE has the function of a plug that connects the conductor WE to the oxide S, the conductor BGE, or the conductor FGE. Note that an example in which the oxide semiconductor S is composed of three layers, i.e., oxides S1, S2, and S3, is shown here.

[0400] In addition, the present embodiment can be appropriately combined with other embodiments shown in this specification.

[0401] (Embodiment 4)

[0402] In the present embodiment, the structures of metal oxides CAC-OS (Cloud-Aligned Composite Oxide Semiconductor) and CAAC-OS (c-axis Aligned Crystalline Oxide Semiconductor), which can be used for the OS transistors described in the above embodiments, are described. Note that in the specification and the like, CAC represents an example of the composition of a function or a material, and CAAC represents an example of a crystal structure.

[0403] <Composition of Metal Oxide>

[0404] CAC-OS or CAC-metal oxide has a conductive function in a part of the material and an insulating function in another part of the material, and has a semiconductor function as a whole. Further, when CAC-OS or CAC-metal oxide is used for the active layer of a transistor, the conductive function is a function that allows electrons (or holes) used as carriers to flow, and the insulating function is a function that does not allow electrons used as carriers to flow. By the complementary action of the conductive function and the insulating function, CAC-OS or CAC-metal oxide can have a switching function (on / off function). By separating the respective functions in CAC-OS or CAC-metal oxide, each function can be maximized.

[0405] CAC-OS or CAC-metal oxide includes a conductive region and an insulating region. The conductive region has the above-described conductive function, and the insulating region has the above-described insulating function. Further, in the material, the conductive region and the insulating region may be separated at the nanoparticle level. In addition, the conductive region and the insulating region may be unevenly distributed in the material. Further, the conductive region may be observed to have a blurred edge and be connected in a cloud shape.

[0406] In CAC-OS or CAC-metal oxide, the conductive region and the insulating region may be dispersed in the material in a size of 0.5 nm or more and 10 nm or less, preferably 0.5 nm or more and 3 nm or less.

[0407] In addition, CAC-OS or CAC-metal oxide is composed of components with different band gaps. For example, CAC-OS or CAC-metal oxide is composed of a component with a wide gap caused by an insulating region and a component with a narrow gap caused by a conductive region. In this structure, when carriers are allowed to flow through, the carriers mainly flow through the component with the narrow gap. In addition, the component with a narrow gap complements the component with a wide gap, and the carriers flow through the component with the wide gap in conjunction with the component with the narrow gap. Therefore, when the above-mentioned CAC-OS or CAC-metal oxide is used in the channel formation region of a transistor, a high current driving force, that is, a large on-state current and a high field effect mobility can be obtained in the on-state of the transistor.

[0408] That is, CAC-OS or CAC-metal oxide may also be referred to as a matrix composite material (matrix composite) or a metal matrix composite material (metal matrix composite).

[0409] <Structure of Metal Oxide>

[0410] Oxide semiconductors are classified into single crystal oxide semiconductors and non-single crystal oxide semiconductors. Examples of non-single crystal oxide semiconductors include CAAC-OS (c-axis aligned crystalline oxide semiconductor), polycrystalline oxide semiconductor, nc-OS (nanocrystalline oxide semiconductor), a-like OS (amorphous-like oxide semiconductor), and amorphous oxide semiconductor.

[0411] CAAC-OS has c-axis orientation, and its multiple nanocrystals are connected in the ab plane direction and the crystal structure has distortion. Note that distortion refers to the part where the lattice arrangement direction changes between the region where the multiple nanocrystals are connected and the region where the lattice arrangement is consistent.

[0412] Although nanocrystals are basically hexagonal, they are not limited to regular hexagons, and there are cases where they are not regular hexagons. In addition, the distortion sometimes has lattice arrangements such as pentagons and heptagons. In addition, no clear grain boundaries are observed near the distortion of CAAC-OS. That is, it can be seen that the formation of grain boundaries can be suppressed by distorting the lattice arrangement. This may be because CAAC-OS can tolerate distortions caused by the following reasons: low density of oxygen atoms in the ab plane direction or changes in the bonding distance between atoms due to substitution of metal elements.

[0413] CAAC-OS has a tendency to have a layered crystalline structure (also referred to as a layered structure), in which layers containing indium and oxygen (hereinafter referred to as In layers) and layers containing element M, zinc, and oxygen (hereinafter referred to as (M, Zn) layers) are stacked. In addition, indium and element M can replace each other. When indium replaces element M in the (M, Zn) layer, this layer can also be expressed as an (In, M, Zn) layer. In addition, when element M replaces indium in the In layer, this layer can also be expressed as an (In, M) layer.

[0414] CAAC-OS is a highly crystalline oxide semiconductor. In addition, no distinct grain boundaries are observed in CAAC-OS, so a decrease in electron mobility due to grain boundaries is not likely to occur. In addition, the crystallinity of an oxide semiconductor sometimes decreases due to the incorporation of impurities or the generation of defects, etc. Therefore, it can be said that CAAC-OS is an oxide semiconductor with few impurities or defects (such as oxygen defects). Therefore, the physical properties of the oxide semiconductor containing CAAC-OS are stable. Therefore, the oxide semiconductor containing CAAC-OS has high heat resistance and high reliability. In addition, CAAC-OS also has stability against high temperatures (so-called thermal budget) in the manufacturing process. Therefore, when using CAAC-OS for an OS transistor, the degree of freedom in the manufacturing process can be expanded.

[0415] In nc-OS, the atomic arrangement in a minute region (for example, a region of 1 nm or more and 10 nm or less, particularly a region of 1 nm or more and 3 nm or less) has periodicity. In addition, no regularity in the crystal orientation is observed between different nanocrystals in nc-OS. Therefore, no orientation is observed in the entire film. Therefore, in some analysis methods, nc-OS may not be distinguishable from a-like OS or an amorphous oxide semiconductor.

[0416] a-like OS is an oxide semiconductor having a structure intermediate between nc-OS and an amorphous oxide semiconductor. a-like OS contains voids or low-density regions. That is, the crystallinity of a-like OS is lower than that of nc-OS and CAAC-OS.

[0417] Oxide semiconductors have various structures and various characteristics. The oxide semiconductor according to one embodiment of the present invention may also include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, a-like OS, nc-OS, and CAAC-OS.

[0418] □ Transistor having an oxide semiconductor □

[0419] Here, the case where the above oxide semiconductor is used for a transistor will be described.

[0420] By using the above oxide semiconductor for a transistor, a transistor with a high field-effect mobility can be achieved. In addition, a transistor with high reliability can be achieved.

[0421] In addition, it is preferable to use an oxide semiconductor with a low carrier concentration for a transistor. When aiming to reduce the carrier concentration of the oxide semiconductor film, the impurity concentration in the oxide semiconductor film can be reduced to reduce the density of defect states. In this specification and the like, a state with a low impurity concentration and a low density of defect states is referred to as "high-purity intrinsic" or "substantially high-purity intrinsic". For example, the carrier concentration of the oxide semiconductor can be less than 8×10 11 cm -3 , preferably less than 1×10 11 cm -3 , more preferably less than 1×10 10 cm -3 and 1×10 -9 cm -3 or more.

[0422] In addition, since the oxide semiconductor film with high-purity intrinsic or substantially high-purity intrinsic has a low density of defect states, it is likely to have a low density of trap states.

[0423] Furthermore, it takes a long time for the charge trapped by the trap state density of the oxide semiconductor to disappear and sometimes acts like a fixed charge. Therefore, sometimes the electrical characteristics of a transistor in which a channel formation region is formed in an oxide semiconductor with a high trap state density are unstable.

[0424] Therefore, in order to stabilize the electrical characteristics of a transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. In order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in the nearby film. Examples of impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, silicon, and the like.

[0425] <Impurity>

[0426] Here, the effects of each impurity in the oxide semiconductor will be described.

[0427] When the oxide semiconductor contains silicon or carbon, which is one of the Group 14 elements, defect energy levels are formed in the oxide semiconductor. Therefore, the concentration of silicon or carbon in the oxide semiconductor and near the interface of the oxide semiconductor (the concentration measured by secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry)) is set to 2×10 18 atoms / cm 3 or less, preferably 2×10 17 atoms / cm 3Below.

[0428] In addition, when the oxide semiconductor contains an alkali metal or an alkaline earth metal, defect levels are sometimes formed to generate carriers. Therefore, a transistor using an oxide semiconductor containing an alkali metal or an alkaline earth metal tends to have a normally-on characteristic. Thus, it is preferable to reduce the concentration of the alkali metal or the alkaline earth metal in the oxide semiconductor. Specifically, the concentration of the alkali metal or the alkaline earth metal in the oxide semiconductor measured by SIMS is set to 1×10 18 atoms / cm 3 or less, preferably 2×10 16 atoms / cm 3 or less.

[0429] When the oxide semiconductor contains nitrogen, electrons are generated as carriers, and the carrier concentration increases, and the oxide semiconductor tends to be n-type. As a result, a transistor using an oxide semiconductor containing nitrogen tends to have a normally-on characteristic. Therefore, it is preferable to reduce nitrogen in the oxide semiconductor as much as possible. For example, the nitrogen concentration in the oxide semiconductor measured by SIMS is less than 5×10 19 atoms / cm 3 , preferably 5×10 18 atoms / cm 3 or less, more preferably 1×10 18 atoms / cm 3 or less, still more preferably 5×10 17 atoms / cm 3 or less.

[0430] Hydrogen contained in the oxide semiconductor reacts with oxygen bonded to a metal atom to generate water, so that oxygen defects are sometimes formed. When hydrogen enters the oxygen defect, electrons are sometimes generated as carriers. In addition, sometimes electrons are generated as carriers because a part of hydrogen bonds to oxygen bonded to a metal atom. Therefore, a transistor using an oxide semiconductor containing hydrogen tends to have a normally-on characteristic. Thus, it is preferable to reduce hydrogen in the oxide semiconductor as much as possible. Specifically, in the oxide semiconductor, the hydrogen concentration measured by SIMS is less than 1×10 20 atoms / cm 3 , preferably less than 1×10 19 atoms / cm 3 , more preferably less than 5×10 18 atoms / cm 3 , still more preferably less than 1×10 18 atoms / cm 3 .

[0431] By using an oxide semiconductor with sufficiently reduced impurities for the channel formation region of a transistor, the transistor can have stable electrical characteristics.

[0432] This embodiment can be appropriately combined with other embodiments in this specification.

[0433] (Embodiment 5)

[0434] In this embodiment, a product example in which the semiconductor device described in the above embodiment is applied to an electronic device will be described.

[0435] 〈Notebook personal computer〉

[0436] A semiconductor device according to one aspect of the present invention can be applied to a display included in an information terminal device. Fig.23A A notebook personal computer, which is one of the information terminal devices, is shown, and it includes a housing 5401, a display unit 5402, a keyboard 5403, a pointing device 5404, and the like.

[0437] 〈Smartwatch〉

[0438] A semiconductor device according to one aspect of the present invention can be applied to a wearable terminal. Fig. 23B A smartwatch, which is one type of wearable terminal, includes a housing 5901, a display unit 5902, operation buttons 5903, a crown 5904, a watch band 5905, and the like. In addition, a display device with a function of a position input device can be used for the display unit 5902. In addition, the function of a position input device can be added by providing a touch panel on the display device. Alternatively, the function of a position input device can be added by providing a photoelectric conversion element, also called a photoelectric sensor, in the pixel portion of the display device. In addition, as the operation buttons 5903, at least one of a power switch for starting the smartwatch, a button for operating the software of the smartwatch, a button for adjusting the volume, and a switch for turning on or off the display unit 5902 can be provided. In addition, Fig. 23B Two operation buttons 5903 are shown in the smartwatch shown, but the number of operation buttons included in the smartwatch is not limited to this. In addition, the crown 5904 is used as a crown for adjusting the time of the smartwatch. In addition, the crown 5904 can be used as an input interface for operating the software of the smartwatch in addition to adjusting the time. In addition, Fig. 23B The smartwatch shown has a structure including the crown 5904, but is not limited to this, and may also have a structure without the crown 5904.

[0439] 〈Video camera〉

[0440] A semiconductor device according to one aspect of the present invention can be applied to a video camera. Fig.23CThe video camera shown includes a first housing 5801, a second housing 5802, a display unit 5803, operation keys 5804, a lens 5805, a connection part 5806, etc. The operation keys 5804 and the lens 5805 are provided in the first housing 5801, while the display unit 5803 is provided in the second housing 5802. Moreover, the first housing 5801 and the second housing 5802 are connected by the connection part 5806, and the angle between the first housing 5801 and the second housing 5802 can be changed by the connection part 5806. The image of the display unit 5803 can also be switched according to the angle between the first housing 5801 and the second housing 5802 formed by the connection part 5806.

[0441] <Mobile phone>

[0442] A semiconductor device according to one embodiment of the present invention can be applied to a mobile phone. Fig.23D A mobile phone having the function of an information terminal is shown. The mobile phone includes a housing 5501, a display unit 5502, a microphone 5503, a speaker 5504, and operation buttons 5505. In addition, a display device with the function of a position input device can also be used for the display unit 5502. In addition, the function of a position input device can be added by providing a touch panel on the display device. Alternatively, the function of a position input device can also be added by providing a photoelectric conversion element, also called a photoelectric sensor, in the pixel portion of the display device. In addition, as the operation button 5505, any one of a power switch for starting the mobile phone, a button for operating the software of the mobile phone, a button for adjusting the volume, and a switch for turning on or off the display unit 5502 can be provided.

[0443] In addition, in Fig.23D two operation buttons 5505 are shown in the mobile phone shown, but the number of operation buttons included in the mobile phone is not limited to this. In addition, although not shown, Fig.23D the mobile phone shown may also include a light-emitting device for use as a flash or illumination.

[0444] <Stationary game console>

[0445] A semiconductor device according to one embodiment of the present invention can be applied to a stationary game console, which is an example of a game console. Fig.23E A game console main body 7520 and a controller 7522 are shown as a stationary game console. The game console main body 7520 can be connected to the controller 7522 in a wireless manner or a wired manner. In addition, although Fig.23E not shown in, the controller 7522 may include a display unit for displaying game images, a touch panel and a control stick, a rotary gripper, a sliding gripper, etc. as input interfaces other than buttons. In addition, the controller 7522 is not limited to Fig.23EThe shape shown can also be changed according to the type of game. For example, in a shooting game such as an FPS (First Person Shooter), a button can be used as a trigger, and a controller in the shape of a gun can be used. Additionally, for example, in a music game, a controller in the shape of a musical instrument or music device can be used. Furthermore, a stationary game console can also be provided with a camera, depth sensor, microphone, etc., and be operated by the gestures and / or voices of game players instead of the shape of the controller.

[0446] 〈Portable Game Console〉

[0447] An example of a game console to which a semiconductor device according to one embodiment of the present invention can be applied is a portable game console. Fig.23F The portable game console shown includes a housing 5201, a display unit 5202, buttons 5203, etc. Note that Figure 23F The portable game console shown is an example, and the configuration, shape, and number of the display unit, buttons, etc. of the portable game console to which a semiconductor device according to one embodiment of the present invention is applied are not limited to Figure 23F the structure shown. In addition, the shape of the housing of the portable game console is not limited to Figure 23F the structure shown.

[0448] As examples of game consoles, stationary game consoles, portable game consoles, etc. have been given above. A semiconductor device according to one embodiment of the present invention can be applied to commercial game consoles (arcades), etc. other than the above.

[0449] 〈Television Device〉

[0450] A semiconductor device according to one embodiment of the present invention can be applied to a television device. Figure 23G The television device shown includes a housing 9000, a display unit 9001, speakers 9003, operation keys 9005 (including a power switch or operation switch), connection terminals 9006, etc. A large display unit 9001, for example, 50 inches or more or 100 inches or more, can be assembled into the television device.

[0451] 〈Moving Body〉

[0452] A semiconductor device according to one embodiment of the present invention can be applied to the periphery of the driver's seat of an automobile as a moving body.

[0453] For example, Figure 23H is a diagram showing the periphery of the front windshield inside an automobile. Figure 23H Shows a display panel 5701, a display panel 5702, a display panel 5703 mounted on the dashboard, and a display panel 5704 mounted on the pillar.

[0454] The display panels 5701 to 5703 can provide navigation information, speedometers, tachometers, driving distances, fuel quantities, gear states, settings of air conditioners, and various other information. Additionally, the user can appropriately change the display content, layout, etc. shown on the display panels, which can improve the design. The display panels 5701 to 5703 can also be used as lighting devices.

[0455] By displaying the images captured by the imaging unit provided on the vehicle body on the display panel 5704, the field of view (blind spot) blocked by the pillar can be supplemented. That is, by displaying the images captured by the imaging unit provided outside the vehicle, the blind spot can be supplemented, thereby improving safety. Additionally, by displaying the images of the parts that cannot be seen, safety can be confirmed more naturally and comfortably. The display panel 5704 can be used as a lighting device.

[0456] 〈Electronic device for electronic advertising〉

[0457] A semiconductor device according to one embodiment of the present invention can be applied to a display for electronic advertising. Figure 24A An example of a digital signage that can be mounted on a wall is shown. Figure 24A The situation where the digital signage 6200 is mounted on the wall 6201 is shown.

[0458] 〈Foldable tablet information terminal〉

[0459] A semiconductor device according to one embodiment of the present invention can be applied to a tablet information terminal. Figure 24B A tablet information terminal having a foldable structure is shown. Figure 24B The illustrated information terminal includes a housing 5321a, a housing 5321b, a display unit 5322, and operation buttons 5323. In particular, the display unit 5322 includes a flexible substrate, and a foldable structure can be achieved by this substrate.

[0460] In addition, the housing 5321a and the housing 5321b are joined by a hinge portion 5321c and can be folded in half by the hinge portion 5321c. Furthermore, the display unit 5322 is provided on the housing 5321a, the housing 5321b, and the hinge portion 5321c.

[0461] In addition, although not shown, Figures 23A to 23C , Figure 23E , Figure 24A and Figure 24B The illustrated electronic device can also have a structure including a microphone and a speaker. By adopting such a structure, for example, a voice input function can be added to the above-mentioned electronic device.

[0462] In addition, although not shown, Figure 23A ,Figure 23B , Figure 23D , Figure 24A and Figure 24B The electronic devices shown may also have a structure including a camera.

[0463] In addition, although not shown, Figures 23A to 23G , Figure 24A and Figure 24B The electronic devices shown may be provided with sensors inside the housing (the sensors having the function of measuring factors such as force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, inclination, vibration, odor or infrared rays, etc.). In particular, by providing a measuring device with a sensor for measuring inclination such as a gyro sensor or an acceleration sensor, it is possible to determine Figure 23D the direction of the mobile phone shown (in which direction the mobile phone is oriented relative to the vertical direction) and automatically switch the screen display of the display unit 5502 according to the direction of the mobile phone.

[0464] In addition, although not shown, Figures 23A to 23G , Figure 24A and Figure 24B The electronic devices shown may also include a device for obtaining biometric information such as fingerprints, veins, irises or voiceprints. By adopting this structure, an electronic device with biometric recognition function can be realized.

[0465] Figures 23A to 23G and Figure 24A The display unit of the electronic devices shown may use a flexible substrate. Specifically, the display unit may also have a structure in which transistors, capacitors, display elements, etc. are provided on the flexible substrate. By using this structure, not only can an electronic device be realized whose housing has a flat surface as shown in Figures 23A to 23G and Figure 24A , but also an electronic device can be realized whose housing has a curved surface such as the dashboard and the pillar shown in Figure 23H .

[0466] As can be used for Figures 23A to 23G , Figure 24A and Figure 24BExamples of the flexible substrate of the display unit include materials that are transparent to visible light, such as polyethylene terephthalate resin (PET), polyethylene naphthalate resin (PEN), polyethersulfone resin (PES), polyacrylonitrile resin, acrylic resin, polyimide resin, polymethyl methacrylate resin, polycarbonate resin, polyamide resin, polycycloolefin resin, polystyrene resin, polyamide-imide resin, polypropylene resin, polyester resin, polyvinyl halide resin, aromatic polyamide resin, and epoxy resin. In addition, mixtures or laminates of these materials can also be used.

[0467] Note that this embodiment can be appropriately combined with other embodiments shown in this specification.

[0468] [Symbol Explanation]

[0469] M1: Transistor, M2: Transistor, M3: Transistor, CA: Capacitor, CB: Capacitor, CF: Capacitor, BIL: Wiring, RBL: Wiring, WBL: Wiring, WOL: Wiring, SL: Wiring, CAL: Wiring, BGL: Wiring, BGL1: Wiring, BGL2: Wiring, BGI: Insulator, FGI: Insulator, BGE: Conductor, FGE: Conductor, PE: Conductor, WE: Conductor, 11: Semiconductor device, 20: Control circuit, 21: Control unit, 22[1]: Voltage generation circuit, 22[P]: Voltage generation circuit, 22[p1]: Voltage generation circuit, 22[p2]: Voltage generation circuit, 22[p3]: Voltage generation circuit, 23A: Circuit, 23B: Circuit, 23IN: Internal circuit, 25: Temperature detection circuit, 25a: Temperature sensor, 25b: Analog-to-digital conversion circuit, 25c: Voltage control circuit, 30: Storage unit, 40: Storage cell array, 50: Peripheral circuit, 51: Word line driver circuit, 52: Bit line driver circuit, 52a: Column decoder, 52b: Precharge circuit, 52c: Sense amplifier, 52d: Write circuit, 53: Row decoder, 54: Output circuit, 56: Control logic circuit, 110: First storage area, 120: Second storage area, 121: Cache memory, 122: Cache memory, 123: Cache memory, 130: Third storage area, 140: Fourth storage area, 200: Storage device, 210: Storage circuit, 220: Storage circuit, 220a: Storage circuit, 220b: Storage circuit, 221: Storage cell, 230: Storage circuit, 230a: Storage circuit, 230b: Storage circuit, 231: Storage cell, 232: Storage cell, 240: Storage circuit, 300: Transistor, 311: Substrate, 313: Semiconductor region, 314a: Low-resistance region, 314b: Low-resistance region, 315: Insulator, 316: Conductor, 320: Insulator, 322: Insulator, 324: Insulator, 326: Insulator, 328: Conductor, 330: Conductor, 350: Insulator, 352: Insulator, 354: Insulator, 356: Conductor, 360: Insulator, 362: Insulator, 364: Insulator, 366: Conductor, 370: Insulator, 372: Insulator, 374: Insulator, 376: Conductor, 380: Insulator, 382: Insulator, 384: Insulator, 386: Conductor, 500: Transistor, 500A: Transistor, 500B: Transistor, 500C: Transistor, 500D: Transistor, 500E: Transistor, 503: Conductor, 503a: Conductor, 503b: Conductor, 505: Conductor, 510: Insulator, 511: Insulator, 512: Insulator, 514: Insulator, 516: Insulator, 518: Conductor, 520: Insulator,522: Insulator, 524: Insulator, 530: Oxide, 530a: Oxide, 530b: Oxide, 530c: Oxide, 531a: Region, 531b: Region, 540a: Conductor, 540b: Conductor, 542a: Conductor, 542b: Conductor, 543a: Region, 543b: Region, 544: Insulator, 545: Insulator, 546: Conductor, 546a: Conductor, 546b: Conductor, 547a: Conductor, 547b: Conductor, 548: Conductor, 550: Insulator, 552: Metal Oxide, 560: Conductor, 560a: Conductor, 560b: Conductor, 570: Insulator, 571: Insulator, 573: Insulator, 574: Insulator, 575: Insulator, 576a: Insulator, 576b: Insulator, 580: Insulator, 581: Insulator, 582: Insulator, 586: Insulator, 600: Capacitor, 610: Conductor, 612: Conductor, 620: Conductor, 630: Insulator, 650: Insulator, 5201: Housing, 5202: Display Unit, 5203: Button, 5321a: Housing, 5321b: Housing, 5321c: Hinge Portion, 5322: Display Unit, 5323: Operation Button, 5401: Housing, 5402: Display Unit, 5403: Keyboard, 5404: Pointing Device, 5501: Housing, 5502: Display Unit, 5503: Microphone, 5504: Speaker, 5505: Operation Button, 5701: Display Panel, 5702: Display Panel, 5703: Display Panel, 5704: Display Panel, 5801: First Housing, 5802: Second Housing, 5803: Display Unit, 5804: Operation Key, 5805: Lens, 5806: Connection Portion, 5901: Housing, 5902: Display Unit, 5903: Operation Button, 5904: Crown, 5905: Watch Band, 6200: Digital Signage, 6201: Wall, 7520: Game Machine Main Body, 7522: Controller, 9000: Housing, 9001: Display Unit, 9003: Speaker, 9005: Operation Key, 9006: Connection Terminal.

Claims

1. A semiconductor device, comprising: A storage device; And A control circuit, Wherein, the storage device includes a first storage circuit operating at a first storage level and a second storage circuit operating at a second storage level, The access speed of the first storage level is faster than that of the second storage level, The first storage circuit includes a first capacitor and a first transistor having a function of holding the charge held by the first capacitor, The second storage circuit includes a second transistor, a second capacitor electrically connected to the gate of the second transistor, and a third transistor having a function of holding the charge held by the second capacitor, The first transistor and the third transistor include a semiconductor layer having an oxide semiconductor, a first gate, and a second gate, And, the control circuit has a function of changing the first storage circuit from the first storage level to the second storage level by inputting a voltage to the second gate of the first transistor and a function of changing the second storage circuit from the second storage level to the first storage level by inputting a voltage to the second gate of the third transistor.

2. The semiconductor device according to claim 1, Wherein the control circuit includes a temperature detection circuit, The temperature detection circuit has a function of outputting a correction voltage corresponding to the temperature near the storage device, And the control circuit has a function of fluctuating the voltage applied to the second gate of each of the first transistor and the third transistor according to the correction voltage.

3. A semiconductor device, comprising: A storage device; And A control circuit, Wherein, the storage device includes a first storage circuit operating at a first storage level and a second storage circuit operating at a second storage level, The access speed of the first storage level is faster than that of the second storage level, The first storage circuit includes a first capacitor and a first transistor having a function of holding the charge held by the first capacitor, The second storage circuit includes a second transistor, a second capacitor electrically connected to the gate of the second transistor, and a third transistor having a function of holding the charge held by the second capacitor, The first transistor and the third transistor include a semiconductor layer having an oxide semiconductor, a first gate, and a second gate, The control circuit has a function of changing the first storage circuit from the first storage level to the second storage level by inputting a voltage to the second gate of the first transistor and a function of changing the second storage circuit from the second storage level to the first storage level by inputting a voltage to the second gate of the third transistor, The control circuit includes a controller, a plurality of voltage generation circuits, and a switching circuit, The storage device has a function of outputting a signal having the usage situation of the storage capacity of the storage device to the controller, And, the controller has a function of controlling the switching circuit such that the voltage output from any one of the plurality of voltage generation circuits is applied to the second gate of the first transistor and the third transistor according to the signal.

4. The semiconductor device according to claim 3, wherein the control circuit includes a temperature detection circuit, the temperature detection circuit having a function of outputting a correction voltage corresponding to the temperature near the storage device, and the control circuit having a function of causing the voltage applied to the second gate of each of the first transistor and the third transistor to fluctuate according to the correction voltage.

5. A semiconductor device, comprising: a storage device; and a control circuit, wherein the storage device includes a first storage circuit operating at a first storage level and a second storage circuit operating at a second storage level, the access speed of the first storage level being faster than that of the second storage level, the first storage circuit including a first capacitor and a first transistor having a function of holding the charge held by the first capacitor, the second storage circuit including a second transistor, a second capacitor electrically connected to the gate of the second transistor, and a third transistor having a function of holding the charge held by the second capacitor, the first transistor and the third transistor including a semiconductor layer having an oxide semiconductor, a first gate, and a second gate, the control circuit having a function of changing the first storage circuit from the first storage level to the second storage level by inputting a voltage to the second gate of the first transistor and a function of changing the second storage circuit from the second storage level to the first storage level by inputting a voltage to the second gate of the third transistor, the control circuit including a controller, a plurality of voltage generation circuits, and a switching circuit, the storage device having a function of outputting a signal having the usage status of the storage capacity of the storage device to the controller, the controller having a function of controlling the switching circuit such that a voltage output from any one of the plurality of voltage generation circuits is applied to the second gate of the first transistor and the third transistor according to the signal, and the first storage circuit including a region overlapping with the second storage circuit.

6. The semiconductor device according to claim 5, wherein the control circuit includes a temperature detection circuit, the temperature detection circuit having a function of outputting a correction voltage corresponding to the temperature near the storage device, and the control circuit having a function of causing the voltage applied to the second gate of each of the first transistor and the third transistor to fluctuate according to the correction voltage.

7. The semiconductor device according to any one of claims 1 to 6, wherein the oxide semiconductor contains one or more materials selected from indium, element M, and zinc, and the element M is aluminum, gallium, yttrium, or tin.

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