Semiconductor Devices

Abstract

To provide a semiconductor device with a novel structure.SOLUTION: A semiconductor device includes: a silicon substrate; and a device provided above the silicon substrate. The device includes: a transistor; and a conductor. The transistor includes a metal oxide to a channel formation region. A conductivity is applied to the silicon substrate. The conductor is electrically connected to a drain of the transistor and the silicon substrate via an open part provided to the device. A heat radiation of the drain of the transistor can be effectively performed via the silicon substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a semiconductor device. [Background technology]

[0002] As a new semiconductor, attention is being drawn to metal oxides that exhibit semiconductor properties, known as oxide semiconductors. The development of transistors using oxide semiconductors is progressing day by day, and for example, Patent Document 1 listed below discloses the configuration of a DC-DC converter in which a transistor using such an oxide semiconductor can be applied to a power transistor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2011 / 0254523 Summary of the Invention [Problem to be solved by the invention]

[0004] Oxide semiconductors such as In-Ga-Zn oxide (also written as IGZO) have a thermal conductivity that is about 1 / 100 that of insulating layers such as silicon oxide. Therefore, when a transistor is operating, it is prone to accumulate heat generated by self-heating when a large current flows between the source and drain of the transistor. This self-heating can cause fluctuations in the transistor's electrical characteristics or element degradation, potentially reducing reliability.

[0005] An object of one embodiment of the present invention is to provide a semiconductor device or the like having a novel structure.An object of one embodiment of the present invention is to provide a semiconductor device or the like having a novel structure with high reliability.An object of one embodiment of the present invention is to provide a semiconductor device or the like having a novel structure that can reduce fluctuations in electrical characteristics of a transistor due to self-heating or the influence of element degradation.

[0006] The problems of one embodiment of the present invention are not limited to the problems listed above. The problems listed above do not preclude the existence of other problems. The other problems are problems not mentioned in this section, which will be described below. Problems not mentioned in this section can be derived by a person skilled in the art from the description in the specification or drawings, and can be extracted as appropriate from these descriptions. One embodiment of the present invention solves at least one of the problems listed above and / or other problems. [Means for solving the problem]

[0007] One embodiment of the present invention is a semiconductor device including a silicon substrate and a device provided above the silicon substrate, the device including a transistor and a conductor, the transistor including a metal oxide in a channel formation region, the silicon substrate being conductive, and the conductor being electrically connected to a drain of the transistor and the silicon substrate through an opening provided in the device.

[0008] One embodiment of the present invention is a semiconductor device comprising a silicon substrate, a device provided above the silicon substrate, a first extraction electrode, and a second extraction electrode, the device having a transistor and a conductor, the transistor having a metal oxide in a channel formation region, the silicon substrate being made conductive, the conductor being electrically connected to the drain of the transistor and the silicon substrate through an opening provided in the device, the first extraction electrode being electrically connected to the conductor connected to the source of the transistor, and the second extraction electrode being electrically connected to the silicon substrate.

[0009] In one aspect of the present invention, the semiconductor device is preferably such that the first extension electrode is electrically connected via a metal wiring to a conductor connected to the source of the transistor.

[0010] In one embodiment of the present invention, the semiconductor device is preferably one in which the second extraction electrode is directly connected to the silicon substrate.

[0011] In one embodiment of the present invention, the semiconductor device is preferably a semiconductor device in which the silicon substrate is imparted with p-type conductivity.

[0012] In one aspect of the present invention, the semiconductor device is preferably one in which the silicon substrate and the device are covered with a resin layer, and the resin layer is provided inside a housing.

[0013] In one aspect of the present invention, the semiconductor device is preferably a semiconductor device in which a heat sink is provided on the silicon substrate via an insulating layer.

[0014] Other aspects of the present invention will be described in the following embodiments and in the drawings. [Effects of the Invention]

[0015] One embodiment of the present invention can provide a semiconductor device or the like having a novel structure. Alternatively, one embodiment of the present invention can provide a highly reliable semiconductor device or the like having a novel structure. Alternatively, one embodiment of the present invention can provide a semiconductor device or the like having a novel structure in which fluctuations in the electrical characteristics of a transistor due to self-heating or influences on element degradation can be reduced.

[0016] The effects of one embodiment of the present invention are not limited to the effects listed above. The effects listed above do not preclude the existence of other effects. The other effects are described below and are not mentioned in this section. Effects not mentioned in this section can be derived by a person skilled in the art from the description in the specification or drawings, and can be extracted as appropriate from these descriptions. One embodiment of the present invention has at least one of the effects listed above and / or other effects. Therefore, one embodiment of the present invention may not have the effects listed above in some cases. [Brief explanation of the drawings]

[0017] [Figure 1] 1A and 1B are a perspective view and a cross-sectional view illustrating one embodiment of the present invention. [Figure 2] 2A, 2B, and 2C are top views illustrating one embodiment of the present invention. [Figure 3] 3A and 3B are a perspective view and a circuit diagram illustrating one embodiment of the present invention. [Figure 4] 4A and 4B are schematic cross-sectional views illustrating one embodiment of the present invention. [Figure 5] 5A, 5B, and 5C are cross-sectional views illustrating an embodiment of the present invention. [Figure 6] 6A, 6B, and 6C are cross-sectional views illustrating one embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view illustrating one embodiment of the present invention. [Figure 8] 8A, 8B, 8C, and 8D are top views illustrating one embodiment of the present invention. [Figure 9] 9A, 9B, and 9C are circuit diagrams, graphs, and block diagrams illustrating one embodiment of the present invention. [Figure 10] FIG. 10 is a schematic cross-sectional view illustrating one embodiment of the present invention. [Figure 11] 11A and 11B are schematic cross-sectional views illustrating one embodiment of the present invention. [Figure 12] 12A and 12B are schematic cross-sectional views illustrating one embodiment of the present invention. [Figure 13] 13A and 13B are schematic cross-sectional views illustrating one embodiment of the present invention. [Figure 14] FIG. 14 is a diagram showing an electronic device. DETAILED DESCRIPTION OF THE INVENTION

[0018] The following describes an embodiment of the present invention. However, one embodiment of the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various changes in form and details can be made without departing from the spirit and scope of the present invention. Therefore, one embodiment of the present invention should not be interpreted as being limited to the description of the embodiment shown below.

[0019] In this specification, the ordinal numbers "first," "second," and "third" are used to avoid confusion between components. Therefore, they do not limit the number of components. Furthermore, they do not limit the order of the components. For example, a component referred to as "first" in one embodiment of this specification may be a component referred to as "second" in another embodiment or in the claims. For example, a component referred to as "first" in one embodiment of this specification may be omitted in another embodiment or in the claims.

[0020] In the drawings, the same elements or elements having similar functions, elements made of the same material, or elements formed at the same time may be given the same reference numerals, and repeated description thereof may be omitted.

[0021] In this specification, for example, the power supply potential VDD may be abbreviated to potential VDD, VDD, etc. This also applies to other components (for example, signals, voltages, circuits, elements, electrodes, wiring, etc.).

[0022] Furthermore, when the same symbol is used for multiple elements, and particularly when it is necessary to distinguish between them, the symbol may be accompanied by an identifying symbol such as "_1", "_2", "[n]", or "[m,n]". For example, the second wiring GL is written as wiring GL[2].

[0023] (Embodiment 1) A structural example of a semiconductor device according to one embodiment of the present invention will be described with reference to FIGS.

[0024] The semiconductor device in this embodiment is a device including a power transistor (also called a power semiconductor) designed to pass a large current through a load. The power transistor is a transistor that handles a much larger amount of power than a display device, a logic circuit, or the like, by applying a large amount of current flowing between an electrode connected to a source and an electrode connected to a drain and a large voltage to the electrode.

[0025] 1A shows a perspective view of a semiconductor device 10 in which a device 11 (sometimes referred to as an element layer) is provided on a silicon substrate 12. The device 11 has a plurality of transistors 23A to 23D, conductors 21A, 21B, and conductors 22A, 22B. The device 11 also has a plurality of openings 24A, 24B that reach the silicon substrate 12.

[0026] Conductors 21A and 21B function as electrodes connected to the sources of transistors 23A to 23D. In the drawings, conductors 21A and 21B are indicated with an "S" indicating the source side. Note that, although the configuration shown in FIG. 1A illustrates two electrodes connected to the source, there may be one or three or more electrodes connected to the source.

[0027] The conductors 22A and 22B function as electrodes connected to the drains of the transistors 23A to 23D. In the drawing, the conductors 22A and 22B are indicated by a "D" indicating the drain side. Note that in the configuration shown in FIG. 1A, two electrodes are connected to the drain, but the number may be one or three or more.

[0028] Although not shown in FIG. 1A, the transistors 23A to 23D each have a region functioning as a gate, a channel formation region, a drain, or a source. The transistor 23A is a transistor provided between the conductor 21A connected to the source and the conductor 22A connected to the drain. The transistor 23B is a transistor provided between the conductor 21A connected to the source and the conductor 22B connected to the drain. The transistor 23C is a transistor provided between the conductor 21B connected to the source and the conductor 22A connected to the drain. The transistor 23D is a transistor provided between the conductor 21B connected to the source and the conductor 22B connected to the drain.

[0029] Transistors 23A to 23D are arranged such that the sources and drains of the plurality of transistors are parallel between conductors 21A, 21B and conductors 22A, 22B. By arranging the plurality of transistors in parallel, a large current can be passed between conductors 21A, 21B and conductors 22A, 22B. Furthermore, because transistors 23A to 23D can be configured using miniaturized transistors with a channel length of 1 μm or less, variations in transistor characteristics can be reduced.

[0030] The transistors 23A to 23D are transistors (referred to as OS transistors) in which a semiconductor layer having a channel formation region is formed using an oxide semiconductor. Note that an oxide semiconductor may also be called a metal oxide or an oxide. Note that the OS transistors will be described as n-channel transistors unless otherwise specified. By reducing the carrier concentration of an oxide semiconductor, the current flowing between the source and drain in an off state (also referred to as an off-state current or a leakage current) can be made extremely low. The details of OS transistors will be described later.

[0031] OS transistors can be easily integrated because they can be freely arranged by stacking them on a silicon substrate, etc. Furthermore, OS transistors can be fabricated at low cost because they can be fabricated using the same manufacturing equipment as transistors whose semiconductor layer containing the channel formation region is made of silicon (Si transistors).

[0032] Furthermore, if an OS transistor includes a back gate electrode in addition to the gate, source, and drain electrodes, it can be a four-terminal semiconductor device. It can be configured as an electrical circuit network in which the input and output of signals flowing between the source and drain can be independently controlled depending on the voltage applied to the gate or back gate electrode. This allows circuit design to be carried out in the same way as with LSIs. Furthermore, OS transistors have superior electrical characteristics to Si transistors in high-temperature environments. Specifically, they have a large ratio of on-current to off-current, even at high temperatures of 100°C to 200°C, preferably 125°C to 150°C, allowing for good switching operation.

[0033] The silicon substrate 12 is a silicon substrate that has been given electrical conductivity. The silicon substrate 12 is a silicon substrate into which an impurity element is introduced to give it n-type or p-type conductivity. By making the silicon substrate 12 a silicon substrate that has been given p-type conductivity, it is possible to increase the thermal conductivity compared to a silicon substrate that has been given n-type conductivity. The silicon substrate 12 may be configured to have a transistor for configuring a logic circuit.

[0034] Providing conductors in openings 24A and 24B connects conductors 22A and 22B to silicon substrate 12. That is, the drains of transistors 23A to 23D are connected to silicon substrate 12 via conductors 22A and 22B and the conductors provided in openings 24A and 24B. Note that the connection between the drains of transistors 23A to 23D and silicon substrate 12 may be via conductors 22A and 22B, or may be configured to be direct connection via the conductors provided in openings 24A and 24B.

[0035] 1A can be configured to dissipate heat generated on the drain side of OS transistors 23A to 23D, which are caused by current flowing through the transistors, to silicon substrate 12 via conductors in openings provided in device 11. This can suppress fluctuations in the electrical characteristics of transistors 23A to 23D or element degradation due to heat generation, resulting in a highly reliable semiconductor device 10.

[0036] FIG. 1B is a cross-sectional view of semiconductor device 10 taken along cross section AB in FIG. 1A. In the cross-sectional view of FIG. 1B, similar to FIG. 1A, device 11 is provided on silicon substrate 12. Device 11 includes transistors 23A and 23B. Transistor 23A has gate electrode 26A and oxide layer 25A functioning as a semiconductor layer. Transistor 23B has gate electrode 26B and oxide layer 25B functioning as a semiconductor layer. Note that oxide layer 25A and oxide layer 25B may be referred to as oxide layer 28 in other drawings.

[0037] In transistor 23A, oxide layer 25A is connected to conductor 21A. Oxide layer 25A is also connected to conductor 22A. Current flowing through transistor 23A flows from the drain (D) side to the source (S) side (shown by thin arrows in the figure). Therefore, in oxide layer 25A, electrons are accelerated in region 27A on the drain side, causing self-heating. Heat from region 27A that generates heat is dissipated to the silicon substrate 12 side via conductor 22A and the conductor provided in opening 24A (shown by thick dotted arrows in the figure).

[0038] In transistor 23B, oxide layer 25B is connected to conductor 21A. Oxide layer 25B is also connected to conductor 22B. Current flowing through transistor 23B flows from the drain (D) side to the source (S) side (shown by thin arrows in the figure). Therefore, in oxide layer 25B, electrons are accelerated in drain-side region 27B, causing self-heating. Heat from heated region 27B is dissipated to the silicon substrate 12 side via conductor 22B and the conductor provided in opening 24B (shown by thick dotted arrows in the figure).

[0039] Transistors 23C and 23D have the same configuration as transistors 23A and 23B. Therefore, heat generated on the drain side of the transistors can be dissipated to silicon substrate 12 via conductors 22A and 22B and conductors provided in openings 24A and 24B.

[0040] 1A and 1B, a semiconductor device according to one embodiment of the present invention includes a silicon substrate and an OS transistor stacked together, and heat generated on the drain side of the transistor is dissipated to the silicon substrate through a conductor provided in the opening. The silicon substrate can function as a heat sink. Fluctuations in the electrical characteristics of the transistor or element degradation due to heat generation can be suppressed, resulting in a highly reliable semiconductor device.

[0041] 2A shows a top view illustrating the configuration of device 11 described in FIGS. 1A and 1B. In the top view of FIG. 2A, transistors 23A to 23D for controlling the electrical connection between conductors 21A and 21B and conductors 22A and 22B are illustrated as X-shaped regions. Openings 24A and 24B, in which conductors for connecting the drains of transistors 23A to 23D to silicon substrate 12 (not shown) are provided, can be provided in regions overlapping with conductors 22A and 22B. Note that conductors 21A and 21B and conductors 22A and 22B shown in the top layout diagram can function as electrodes for connecting external wiring.

[0042] The shape of the conductors 21A, 21B and 22A, 22B functioning as electrodes as viewed from above is preferably such that the distance from the external connection wiring to each transistor is equal. For example, a circular shape or a triangular shape as shown in FIG. 2A is preferable. This configuration makes it possible to equalize the wiring resistance from the wiring connected to the conductors 21A, 21B and 22A, 22B by wire bonding or the like to the multiple transistors.

[0043] 2B shows an enlarged top view of the region where transistor 23B shown in FIG. 2A is provided. In FIG. 2B, a plurality of island-shaped oxide layers 28 are provided between comb-shaped electrodes extending from conductor 21A and conductor 22B. Transistor 23B shown in FIG. 2A can be represented as transistors 23B_1 and 23B_2 provided at both ends of conductor 22B.

[0044] In Fig. 2C, the electrodes represented by conductor 21A and conductor 22B are shown by dotted lines. Fig. 2C also shows conductors 26B_1 and 26B_2 functioning as gate electrodes superimposed on island-shaped oxide layer 28, and conductor 29 functioning as a back gate electrode.

[0045] 3A also shows a perspective view of the transistor 23B (a transistor applicable to the transistors 23A to 23D is also referred to as the transistor 23) in the X and Y directions shown in FIG. 2C. FIG. 3A illustrates the conductor 26B_1 and the conductor 29 provided so as to overlap the island-shaped oxide layer 28. In FIG. 3A, the conductor 29 is illustrated as an electrode BGE as a back gate electrode. In FIG. 3A, the conductor 26B_1 is illustrated as an electrode TGE as a top gate electrode. In FIG. 3A, one of the island-shaped oxide layer 28 separated by the conductor 26B_1 and the conductor 29 is illustrated as a terminal "S," and the other is illustrated as a terminal "D." The transistor 23 illustrated in FIG. 3A can be represented by the symbol shown in FIG. 3B. The structure of the transistor will be described in detail in Embodiment 2.

[0046] Next, with reference to FIGS. 4A, 4B, and 5A to 5C, modifications of the schematic cross-sectional view of the semiconductor device 10 described in FIG. 1B will be described.

[0047] 1B, semiconductor device 10A shown in Fig. 4A illustrates a configuration example in which electrodes for connection to external extraction electrodes or external metal wiring are arranged on the top surface of device 11. In the configuration example of Fig. 4A, conductor 21A connected to the sources of transistors 23A and 23B and conductors 22A and 22B connected to the drains of transistors 23A and 23B can be arranged on the same side, that is, the top surface of device 11.

[0048] 4B illustrates a configuration example in which an external extraction electrode or an electrode connected to external metal wiring is disposed on the top surface of device 11, which is different from the configuration in FIG. 4A. In the configuration example in FIG. 4B, the sources of transistors 23A and 23B are connected to conductor 31A provided in electrode layer 30 above device 11 via conductor 21A, and the drains of transistors 23A and 23B are connected to conductor 22A or 22B and conductor 31B provided in electrode layer 30 above device 11 via silicon substrate 12. In semiconductor device 10B shown in FIG. 4B, electrodes can be disposed on the same side, i.e., the top surface of device 11, as in FIG. 4A.

[0049] Unlike FIGS. 4A and 4B, semiconductor device 10C shown in FIG. 5A illustrates a configuration example in which silicon substrate 12 also functions as an electrode for connecting to an external lead-out electrode or an electrode for connecting to external metal wiring. In the configuration example of FIG. 5A, conductor 31A provided in electrode layer 30 above device 11 via conductor 21A connected to the sources of transistors 23A and 23B, and silicon substrate 12 below device 11 via conductors 22A and 22B connected to the drains of transistors 23A and 23B, can be arranged on different sides. By using silicon substrate 12 as an electrode, the area for bonding an external lead-out electrode or metal wiring for wire bonding can be increased, making electrical connection easier.

[0050] In the semiconductor device 10D shown in FIG. 5B, a configuration different from that shown in FIG. 5A is provided. Conductor 31A provided in electrode layer 30 above device 11 can be arranged on different sides of silicon substrate 12, via conductor 21A connected to the sources of transistors 23A and 23B. Conductors 22A and 22B below the oxide layer connected to the drains of transistors 23A and 23B can be arranged on different sides of silicon substrate 12. Using the silicon substrate 12 as an electrode facilitates connection to an external electrode or metal wiring for wire bonding. Furthermore, arranging conductors 22A and 22B below the oxide layer shortens the path for heat dissipation.

[0051] Although the semiconductor device 10D shown in Fig. 5B is configured such that the silicon substrate 12 is connected to an external lead electrode or to metal wiring that is wire-bonded, other configurations are also possible. For example, as in the semiconductor device 10E shown in Fig. 5C, electrodes can be arranged on the same side, i.e., the top surface of the device 11, via conductors 31A, 31B, etc., provided on the electrode layer 30. By using this configuration, the electrodes can be arranged on the same side, i.e., the top surface of the device 11, in the configuration of Fig. 5B as in Fig. 4A.

[0052] 6A to 6C show examples of cross-sectional schematic diagrams of an electronic component when the semiconductor device 10 described above is mounted in a housing. Note that an electronic component that includes the semiconductor device 10 in a housing may also be called a semiconductor device because it is a device that has transistors that utilize the properties of semiconductors.

[0053] The cross-sectional schematic diagram of electronic component 100A shown in Figure 6A includes semiconductor device 10, metal wiring 104A and 104B, extraction electrodes 105A and 105B, and resin layer 103 within housing 106. Semiconductor device 10 is fixed to substrate 101 within housing 106 with adhesive layer 102. Note that semiconductor device 10 shown in Figure 6A is configured to be connected to the extraction electrodes on the top surface of device 11 shown in Figures 4A and 4B. Substrate 101 and adhesive layer 102 are preferably made of materials with higher thermal conductivity than the surrounding constituent materials in order to enhance the heat dissipation properties of the silicon substrate.

[0054] The semiconductor device 10 is covered with a resin layer 103 within a housing 106. The extraction electrode 105A is connected to an electrode on the top surface of a device included in the semiconductor device 10 via a metal wiring 104A. The extraction electrode 105B is connected to an electrode on the top surface of a device included in the semiconductor device 10 via a metal wiring 104B.

[0055] The cross-sectional schematic diagram of electronic component 100B shown in Figure 6B includes semiconductor device 10, metal wiring 104A, extraction electrodes 105A and 105B, and resin layer 103 within housing 106. Semiconductor device 10 is fixed to substrate 101 within housing 106 with adhesive layer 102. Note that semiconductor device 10 shown in Figure 6B is configured so that it is connected to extraction electrodes on the top surface of device 11 shown in Figures 5A and 5B and on the silicon substrate 12 side.

[0056] The semiconductor device 10 is covered with a resin layer 103 within a housing 106. The extraction electrode 105A is connected to an electrode on the top surface of the device of the semiconductor device 10 via a metal wiring 104A. The extraction electrode 105B is directly connected to the silicon substrate of the semiconductor device 10.

[0057] The cross-sectional schematic diagram of electronic component 100C shown in Figure 6C includes semiconductor device 10, metal wiring 104A, extraction electrodes 105A and 105B, and resin layer 103 within housing 106. Semiconductor device 10 is fixed to substrate 101 within housing 106 with adhesive layer 102 via extraction electrode 105B. Semiconductor device 10 shown in Figure 6C is configured to be connected to extraction electrodes on the top surface of device 11 shown in Figures 5A and 5B and on the silicon substrate 12 side.

[0058] The semiconductor device 10 is covered with a resin layer 103 within a housing 106. The extraction electrode 105A is connected to an electrode on the top surface of the device of the semiconductor device 10 via a metal wiring 104A. The extraction electrode 105B is directly connected to the silicon substrate of the semiconductor device 10.

[0059] 6A to 6C can be configured to be connected to a heat sink. Fig. 7 shows an electronic component 100D in which a heat sink 107 is provided on the substrate 101 side. This configuration can improve heat dissipation from the silicon substrate 12 side.

[0060] Next, FIGS. 8A to 8D illustrate variations of the top view of device 11 illustrated in FIG. 2A.

[0061] 2A, the device 11A shown in Fig. 8A illustrates conductors 21A and 21B, conductors 22A and 22B, and an X-shaped region 23R in which transistors 23A to 23D are provided. The device 11A shown in Fig. 8A illustrates a configuration in which openings 24A and 24B reaching the silicon substrate 12 connect the silicon substrate 12 to the drains of the transistors 23A to 23D in regions overlapping with the conductors 22A and 22B connected to the drains of the transistors 23A to 23D.

[0062] Device 11B shown in Fig. 8B illustrates conductors 21A and 21B, conductors 22A and 22B, and region 23R. Device 11B shown in Fig. 8B is configured such that transistors can be provided on silicon substrate 12 in regions 51A and 51B of silicon substrate 12 that overlap with conductors 21A and 21B connected to the sources of transistors 23A to 23D. This configuration allows a logic circuit to be configured at a position away from openings 24A and 24B through which self-generated drain heat is dissipated.

[0063] In the device 11C shown in FIG. 8C, conductors 21A, 21B, conductors 22A, 22B, and region 23R are illustrated. In the device 11C shown in FIG. 8C, a configuration is illustrated in which the silicon substrate 12 and the drains of transistors 23A to 23D are connected by openings 24C, 24D reaching the silicon substrate 12 in a region overlapping with the region 23R. With this configuration, the heat generated by the drain can be dissipated, and the heat of the transistor can be made uniform to stabilize the transistor characteristics. Also, compared with a configuration in which wiring by conductors is routed to the silicon substrate 12, there are effects such as reducing the resistance of the wiring or being able to dissipate heat through a short path.

[0064] Also, as illustrated in the device 11D of FIG. 8D, a configuration can be adopted in which the configuration of the device 11A illustrated in FIG. 8A and the configuration of the device 11C illustrated in FIG. 8C are combined.

[0065] In FIGS. 9A to 9D, operation examples and application examples of the semiconductor device and the electronic component described above are shown.

[0066] FIG. 9A illustrates a state in which a current ID flows between the source (S) and the drain (D) when a voltage VG is applied to the gate of the transistor 23 included in the semiconductor device 20 and a voltage VBG is applied to the back gate.

[0067] FIG. 9B is a schematic diagram of a graph representing the current-voltage characteristics of the transistor 23 illustrated in FIG. 9A. By switching the back gate voltage between voltages VBG_A, VBG_B (<VBG_A), states with different electrical characteristics can be switched. For example, when the back gate voltage is the voltage VBG_A, the amount of current flowing between the source (S) and the drain (D) when the transistor 23 is on is increased, and when the back gate voltage is the voltage VBG_B, the amount of current flowing between the source (S) and the drain (D) when the transistor 23 is off is made extremely low.

[0068] By configuring the transistor 23 of the semiconductor device 10 that functions as a power transistor with an OS transistor, it is possible to configure the semiconductor device 10 within a battery protection circuit 60, such as a power storage device 199 equipped with a battery 61 as shown in Figure 9C.

[0069] As described above, in the semiconductor device according to one embodiment of the present invention, a silicon substrate and an OS transistor are stacked, and heat generated on the drain side of the transistor can be dissipated to the silicon substrate through the opening. That is, the silicon substrate can function as a heat sink. Therefore, fluctuations in the electrical characteristics of the transistor or element degradation due to heat generation can be suppressed, resulting in a highly reliable semiconductor device.

[0070] (Embodiment 2) In this embodiment mode, an example of a cross-sectional structure of the semiconductor device described in the above embodiment mode will be described with reference to the drawings.

[0071] The semiconductor device shown in Fig. 10 has a transistor 23 included in a device 11 provided on a silicon substrate 12. The semiconductor device shown in Fig. 10 also shows a conductor 21 connected to the source of the transistor 23 and a conductor 22 connected to the drain. The semiconductor device shown in Fig. 10 also shows an opening 24 extending from the conductor 22 to the silicon substrate 12, and this opening 24 corresponds to the openings 24A and 24B described in the first embodiment. Fig. 11A is a cross-sectional view of the transistor 23 in the channel length direction, and Fig. 11B is a cross-sectional view of the transistor 23 in the channel width direction.

[0072] The transistor 23 is an OS transistor corresponding to the transistors 23A to 23D described in Embodiment 1. The transistor 23 has a small off-state current. Therefore, the power consumption of an electronic device including the semiconductor device can be reduced.

[0073] The silicon substrate 12 is a substrate imparted with p-type conductivity by introducing boron or the like to enhance thermal conductivity. The p-type conductivity of the silicon substrate can improve thermal conductivity compared to a silicon substrate imparted with n-type conductivity or a silicon substrate without conductivity. The silicon substrate may also be a substrate imparted with n-type conductivity by arsenic, phosphorus, or the like. The silicon substrate 12 may be configured to include p-channel or n-channel transistors.

[0074] On the silicon substrate 12, an insulator 320, an insulator 322, an insulator 324, and an insulator 326 are stacked in this order.

[0075] The insulators 320, 322, 324, and 326 can be formed using, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, aluminum nitride, or the like.

[0076] In this specification, silicon oxynitride refers to a material whose composition contains more oxygen than nitrogen, silicon nitride oxide refers to a material whose composition contains more nitrogen than oxygen, aluminum oxynitride refers to a material whose composition contains more oxygen than nitrogen, and aluminum nitride oxide refers to a material whose composition contains more nitrogen than oxygen.

[0077] The insulator 322 may function as a planarizing film that flattens steps of the underlying silicon substrate 12, etc. For example, the upper surface of the insulator 322 may be planarized by a planarization process using a chemical mechanical polishing (CMP) method or the like to enhance flatness.

[0078] The insulator 324 is preferably a film having a barrier property that prevents hydrogen and impurities from diffusing from the silicon substrate 12 or the like to the region where the transistor 23 is provided.

[0079] An example of a film having barrier properties against hydrogen is silicon nitride formed by CVD. Here, hydrogen diffusion into a semiconductor element having an oxide semiconductor, such as the transistor 23, may degrade the characteristics of the semiconductor element. Therefore, it is preferable to use a film that suppresses hydrogen diffusion between the transistor 23 and the silicon substrate 12. Specifically, the film that suppresses hydrogen diffusion is a film that releases a small amount of hydrogen.

[0080] The amount of desorbed hydrogen can be analyzed using, for example, thermal desorption spectroscopy (TDS) etc. For example, the amount of desorbed hydrogen from the insulator 324 is calculated by TDS analysis as follows: when the surface temperature of the film is in the range of 50°C to 500°C, the amount of desorbed hydrogen converted into hydrogen atoms is 10 x 10 per area of ​​the insulator 324. 15 atoms / cm 2 Less than or equal to 5 x 10 15 atoms / cm 2 The following is fine.

[0081] It is preferable that the insulator 326 has a lower dielectric constant than the insulator 324. For example, the relative dielectric constant of the insulator 326 is preferably less than 4, and more preferably less than 3. Furthermore, for example, the relative dielectric constant of the insulator 326 is preferably 0.7 times or less, and more preferably 0.6 times or less, the relative dielectric constant of the insulator 324. By using a material with a low dielectric constant as the interlayer film, the parasitic capacitance that occurs between wirings can be reduced.

[0082] Furthermore, conductors 328 and 330, which connect the silicon substrate 12 and the transistor 23, are embedded in the insulators 320, 322, 324, and 326. The conductors 328 and 330 function as plugs or wiring. Furthermore, for conductors that function as plugs or wiring, the same reference numeral may be used to refer to multiple structures. Furthermore, in this specification and the like, the wiring and the plug connecting to the wiring may be integrated. That is, there are cases where a portion of the conductor functions as wiring, and cases where a portion of the conductor functions as a plug.

[0083] The materials for each plug and wiring (conductor 328, conductor 330, etc.) can be a conductive material such as a metal material, an alloy material, a metal nitride material, or a metal oxide material, and can be used in a single layer or a stacked layer. It is preferable to use a high-melting-point material such as tungsten or molybdenum, which has both heat resistance and conductivity, and tungsten is preferred. Alternatively, it is preferable to form the wiring from a low-resistance conductive material such as aluminum or copper. Using a low-resistance conductive material can reduce the wiring resistance.

[0084] A wiring layer may be provided over the insulator 326 and the conductor 330. For example, in FIG. 10 , an insulator 350, an insulator 352, and an insulator 354 are stacked in this order. A conductor 356 is formed in the insulator 350, the insulator 352, and the insulator 354. The conductor 356 functions as a plug or wiring that connects the silicon substrate 12 and the transistor 23. The conductor 356 can be formed using the same material as the conductor 328 or the conductor 330.

[0085] Note that, for example, the insulator 350 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 356 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in an opening provided in the insulator 350 having a barrier property against hydrogen. With this configuration, the silicon substrate 12 and the transistor 23 can be separated by a barrier layer, and diffusion of hydrogen from the silicon substrate 12 to the transistor 23 can be suppressed.

[0086] As the conductor having a barrier property against hydrogen, for example, tantalum nitride or the like may be used. Furthermore, by stacking tantalum nitride and highly conductive tungsten, it is possible to suppress the diffusion of hydrogen from the silicon substrate 12 while maintaining the conductivity of the wiring. In this case, it is preferable that the tantalum nitride layer having a barrier property against hydrogen be in contact with the insulator 350 having a barrier property against hydrogen.

[0087] An insulator 510, an insulator 512, an insulator 514, and an insulator 516 are stacked in this order over the insulator 354. Any of the insulator 510, the insulator 512, the insulator 514, and the insulator 516 is preferably formed using a substance that has a barrier property against oxygen and hydrogen.

[0088] For example, the insulators 510 and 514 are preferably films having barrier properties that prevent hydrogen and impurities from diffusing from the silicon substrate 12 or the like to the region where the transistor 23 is provided. Therefore, it is preferable to use the same material as the insulator 324.

[0089] An example of a film having barrier properties against hydrogen is silicon nitride formed by a CVD method. Here, hydrogen diffusion into a semiconductor element having an oxide semiconductor, such as the transistor 23, may degrade the characteristics of the semiconductor element. Therefore, it is preferable to use a film that suppresses hydrogen diffusion between the silicon substrate 12 and the transistor 23. Specifically, a film that suppresses hydrogen diffusion is a film that desorbs a small amount of hydrogen.

[0090] As a film having a barrier property against hydrogen, for example, the insulators 510 and 514 are preferably made of a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

[0091] In particular, aluminum oxide has a high blocking effect of preventing the permeation of both oxygen and impurities such as hydrogen and moisture, which can cause fluctuations in the electrical characteristics of a transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen and moisture from entering the transistor 23 during and after the transistor manufacturing process. Furthermore, aluminum oxide can suppress the release of oxygen from the metal oxide that constitutes the transistor 23. Therefore, aluminum oxide is suitable for use as a protective film for the transistor 23.

[0092] For example, the insulator 512 and the insulator 516 can be formed using a material similar to that of the insulator 320. By using a material with a relatively low dielectric constant for these insulators, parasitic capacitance between wirings can be reduced. For example, the insulators 512 and 516 can be formed using a silicon oxide film, a silicon oxynitride film, or the like.

[0093] A conductor 518 and a conductor constituting the transistor 23 (for example, the conductor 503) are embedded in the insulators 510, 512, 514, and 516. The conductor 518 functions as a plug or wiring that connects the silicon substrate 12 and the transistor 23. The conductor 518 can be formed using a material similar to that of the conductor 328 or the conductor 330.

[0094] In particular, the conductor 518 in the region in contact with the insulator 510 and the insulator 514 is preferably a conductor having a barrier property against oxygen, hydrogen, and water. With this structure, the silicon substrate 12 and the transistor 23 can be separated by a layer having a barrier property against oxygen, hydrogen, and water, and diffusion of hydrogen from the silicon substrate 12 to the transistor 23 can be suppressed.

[0095] Above the insulator 516, the transistor 23 is provided.

[0096] As shown in Figures 11A and 11B, transistor 23 has a conductor 503 arranged so as to be embedded in insulator 514 and insulator 516, an insulator 520 arranged on insulator 516 and conductor 503, an insulator 522 arranged on insulator 520, an insulator 524 arranged on insulator 522, an oxide 530a arranged on insulator 524, an oxide 530b arranged on oxide 530a, conductors 542a and 542b arranged apart from each other on oxide 530b, an insulator 580 arranged on conductors 542a and 542b and having an opening formed therein overlapping with conductors 542a and 542b, an oxide 530c arranged on the bottom and side surfaces of the opening, an insulator 550 arranged on the surface on which oxide 530c is formed, and a conductor 560 arranged on the surface on which insulator 550 is formed.

[0097] 11A and 11B, it is preferable to arrange an insulator 544 between the oxide 530a, the oxide 530b, the conductor 542a, and the conductor 542b and the insulator 580. It is preferable to arrange an insulator 544 between the oxide 530a, the oxide 530b, the conductor 542a, and the conductor 542b and the insulator 580 and between the oxide 530a, the conductor 530b, and the conductor 542b and the insulator 580 and between the oxide 530a, the conductor 530b, and the conductor 542b and the insulator 580 and the conductor 560a and the conductor 560b and between the oxide 530a, the conductor 530b, and the conductor 542b and the insulator 580 and the conductor 560a and the conductor 560b and between the oxide 530a, the conductor 530b, and the conductor 542b and the insulator 580 and the conductor 560a and the insulator 550 ...44 and the insulator 574 and the insulator 574 and the insulator 580 and the conductor 560 and the insulator 550 and between the oxide 530a, the conductor 530b, and the conductor 542b and the insulator 560a and the conductor 560b and

[0098] In the following, the oxide 530a, the oxide 530b, and the oxide 530c may be collectively referred to as the oxide 530.

[0099] Although the transistor 23 has a three-layer structure of oxides 530a, 530b, and 530c in and around the channel formation region, the present invention is not limited to this structure. For example, the transistor 23 may have a single layer of oxide 530b, a two-layer structure of oxides 530b and 530a, a two-layer structure of oxides 530b and 530c, or a stacked structure of four or more layers. Although the transistor 23 has a two-layer structure, the present invention is not limited to this structure. For example, the conductor 560 may have a single-layer structure or a stacked structure of three or more layers. The transistor 23 shown in FIGS. 10, 11A, and 11B is merely an example, and the transistor 23 is not limited to this structure. An appropriate transistor may be used depending on the circuit configuration and driving method.

[0100] Here, the conductor 560 functions as the gate electrode of the transistor 23, and the conductors 542a and 542b function as the source electrode and drain electrode, respectively. As described above, the conductor 560 is formed so as to be embedded in the opening of the insulator 580 and in the region sandwiched between the conductors 542a and 542b. The arrangements of the conductors 560, 542a, and 542b are selected in a self-aligned manner with respect to the opening of the insulator 580. That is, in the transistor 23, the gate electrode can be arranged in a self-aligned manner between the source electrode and the drain electrode. Therefore, the conductor 560 can be formed without providing an alignment margin, thereby reducing the area occupied by the transistor 23. This allows for miniaturization and high integration of semiconductor devices.

[0101] Furthermore, since the conductor 560 is formed in a self-aligned manner in the region between the conductor 542a and the conductor 542b, the conductor 560 does not have a region that overlaps with the conductor 542a or the conductor 542b. This reduces the parasitic capacitance formed between the conductor 560 and the conductor 542a and the conductor 542b. This improves the switching speed of the transistor 23, allowing it to have high frequency characteristics.

[0102] The conductor 560 may function as a first gate (also referred to as a top gate) electrode. The conductor 503 may function as a second gate (also referred to as a bottom gate) electrode. In this case, the threshold voltage of the transistor 23 can be controlled by changing the potential applied to the conductor 503 independently of the potential applied to the conductor 560. In particular, applying a negative potential to the conductor 503 can increase the threshold voltage of the transistor 23 above 0 V and reduce the off-state current. Therefore, applying a negative potential to the conductor 503 can reduce the drain current when the potential applied to the conductor 560 is 0 V compared to when a negative potential is not applied.

[0103] The conductor 503 is arranged to have a region overlapping with the oxide 530 and the conductor 560. In this manner, when a potential is applied 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, a transistor structure in which the channel formation region is electrically surrounded by the electric fields of the first gate electrode and the second gate electrode is referred to as a surrounded channel (s-channel) structure.

[0104] The conductor 503 has a structure similar to that of the conductor 518, in which 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 further inward. Note that although the transistor 23 has a structure in which the conductors 503a and 503b are stacked, the present invention is not limited to this. For example, the conductor 503 may have a single layer structure or a stacked structure of three or more layers.

[0105] Here, the conductor 503a is preferably made of a conductive material that has the function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, copper atoms, etc. (the impurities are less likely to permeate). Alternatively, it is preferably made of a conductive material that has the function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) (the oxygen is less likely to permeate). Note that in this specification and the like, the function of suppressing the diffusion of impurities or oxygen refers to the function of suppressing the diffusion of any one or all of the impurities or oxygen.

[0106] For example, the conductor 503a has a function of suppressing the diffusion of oxygen, so that the conductor 503b can be prevented from being oxidized and its conductivity from decreasing.

[0107] Furthermore, when the conductor 503 also functions as a wiring, it is preferable that the conductor 503b be made of a highly conductive material containing tungsten, copper, or aluminum as a main component. In this case, the conductor 503a is not necessarily provided. Note that although the conductor 503b is illustrated as a single layer, it may have a multilayer structure, for example, a multilayer structure of titanium or titanium nitride and the above-mentioned conductive material.

[0108] The insulators 520, 522, and 524 function as a second gate insulating film.

[0109] Here, the insulator 524 in contact with the oxide 530 preferably contains more oxygen than the oxygen required for the stoichiometric composition. That is, an excess oxygen region is preferably formed in the insulator 524. By providing such an insulator containing excess oxygen in contact with the oxide 530, oxygen vacancies in the oxide 530 can be reduced and the reliability of the transistor 23 can be improved.

[0110] Specifically, it is preferable to use an oxide material from which a portion of oxygen is released by heating as an insulator having an excess oxygen region. The oxide material from which oxygen is released by heating is an oxide material from which the amount of released oxygen converted to oxygen atoms is 1.0 × 10 in TDS (Thermal Desorption Spectroscopy) analysis. 18 atoms / cm 3 or more, preferably 1.0 × 10 19 atoms / cm 3 More preferably, 2.0 × 10 19 atoms / cm 3 or more, or 3.0 x 10 20 atoms / cm 3 The oxide film is one having the above properties. The surface temperature of the film during the 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.

[0111] Furthermore, the oxide 530 may be brought into contact with the insulator having the excess oxygen region and subjected to one or more of heat treatment, microwave treatment, and RF treatment. By performing such treatment, water or hydrogen in the oxide 530 can be removed. For example, a reaction occurs in the oxide 530 that breaks the VOH bond, in other words, "V O H→V O +H" reaction occurs, resulting in dehydrogenation. Some of the generated hydrogen may combine with oxygen to form HO and be removed from the oxide 530 or an insulator near the oxide 530. Some of the hydrogen may also be diffused or captured (also called gettering) in the conductor 542.

[0112] The microwave treatment is preferably performed using, for example, an apparatus having a power supply for generating high-density plasma or an apparatus having a power supply for applying RF to the substrate side. For example, high-density oxygen radicals can be generated by using a gas containing oxygen and high-density plasma. Furthermore, by applying RF to the substrate side, oxygen radicals generated by high-density plasma can be efficiently introduced into the oxide 530 or an insulator near the oxide 530. The microwave treatment may be performed under a pressure of 133 Pa or higher, preferably 200 Pa or higher, and more preferably 400 Pa or higher. The gases introduced into the microwave treatment apparatus may be, for example, oxygen and argon, with the oxygen flow ratio (O2 / (O2+Ar)) being 50% or lower, preferably 10% to 30%.

[0113] In addition, in the manufacturing process of the transistor 23, heat treatment is preferably performed in a state where the surface of the oxide 530 is exposed. The heat treatment may be performed, for example, at a temperature of 100° C. to 450° C., more preferably 350° C. to 400° C. Note that the heat treatment is performed in an atmosphere of nitrogen gas or an inert gas, or an atmosphere containing an oxidizing gas at 10 ppm or more, 1% or more, or 10% or more. For example, the heat treatment is preferably performed in an oxygen atmosphere. This supplies oxygen to the oxide 530, thereby eliminating oxygen vacancies (V O ) can be reduced. The heat treatment may be performed under reduced pressure. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas after the heat treatment in a nitrogen gas or inert gas atmosphere to compensate for the desorbed oxygen. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas, and then the heat treatment may be performed in a nitrogen gas or inert gas atmosphere.

[0114] By subjecting the oxide 530 to oxygen addition treatment, oxygen vacancies in the oxide 530 are repaired by the supplied oxygen. In other words, O+O→null reaction can be promoted. Furthermore, the hydrogen remaining in the oxide 530 reacts with the oxygen supplied to the oxide 530, and the hydrogen can be removed as HO (dehydration). As a result, the hydrogen remaining in the oxide 530 recombines with the oxygen vacancies to form V O The formation of H can be suppressed.

[0115] When the insulator 524 has an excess oxygen region, the insulator 522 preferably has a function of suppressing the diffusion of oxygen (for example, oxygen atoms, oxygen molecules, etc.) (preferably making the oxygen less permeable).

[0116] The insulator 522 preferably has a function of suppressing diffusion of oxygen and impurities, which prevents oxygen contained in the oxide 530 from diffusing toward the insulator 520. Furthermore, reaction of the conductor 503 with oxygen contained in the insulator 524 and the oxide 530 can be suppressed.

[0117] The insulator 522 is preferably a single-layer or multi-layer insulator containing a high-k material, such as aluminum oxide, hafnium oxide, oxide containing aluminum and hafnium (hafnium aluminate), tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST). As transistors become smaller and more highly integrated, thinner gate insulating films can cause problems such as leakage current. Using a high-k material for the insulator that functions as the gate insulating film makes it possible to reduce the gate potential during transistor operation while maintaining the physical film thickness.

[0118] In particular, an insulator containing an oxide of one or both of aluminum and hafnium, which is an insulating material that has the function of suppressing the diffusion of impurities and oxygen (i.e., the oxygen is less likely to permeate), is preferably used. As an insulator containing an oxide of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate) is preferably used. When the insulator 522 is formed using such a material, the insulator 522 functions as a layer that suppresses oxygen release from the oxide 530 and the intrusion of impurities such as hydrogen into the oxide 530 from the periphery of the transistor 23.

[0119] Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to these insulators. Alternatively, these insulators may be nitrided. Silicon oxide, silicon oxynitride, or silicon nitride may be stacked on the above insulators.

[0120] Furthermore, it is preferable that the insulator 520 is thermally stable. For example, silicon oxide and silicon oxynitride are suitable because they are thermally stable. Furthermore, by combining a high-k insulator with silicon oxide or silicon oxynitride, it is possible to obtain the insulator 520 having a thermally stable layered structure with a high dielectric constant.

[0121] 11A and 11B, the second gate insulating film has a three-layer stack structure including insulators 520, 522, and 524. However, the second gate insulating film may have a single-layer, two-layer, or four or more-layer stack structure. In this case, the second gate insulating film is not limited to a stack structure made of the same material, and may have a stack structure made of different materials.

[0122] The transistor 23 preferably uses a metal oxide functioning as an oxide semiconductor for the oxide 530 including the channel formation region. For example, a metal oxide such as In-M-Zn oxide (wherein the element M is one or more elements selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, etc.) may be used for the oxide 530. In particular, the In-M-Zn oxide applicable to the oxide 530 is preferably CAAC-OS (C-Axls Aligned Crystal Oxide Semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor). Alternatively, an In-Ga oxide or an In-Zn oxide may be used for the oxide 530. CAAC-OS and CAC-OS will be described later. Note that, when it is desired to increase the on-state current of the transistor 23, it is preferable to use an In-Zn oxide for the oxide 530. When an In-Zn oxide is used for the oxide 530, examples include a stacked structure in which an In-Zn oxide is used for the oxide 530a and an In-M-Zn oxide is used for the oxide 530b and the oxide 530c, or a stacked structure in which an In-M-Zn oxide is used for the oxide 530a and an In-Zn oxide is used for either the oxide 530b or the oxide 530c.

[0123] Furthermore, it is preferable to use a metal oxide with a low carrier concentration for the transistor 23. To lower the carrier concentration of the metal oxide, the impurity concentration in the metal oxide should be lowered to lower the defect state density. In this specification and the like, a low impurity concentration and a low defect state density are referred to as high-purity intrinsic or substantially high-purity intrinsic. Note that impurities in metal oxides include, for example, hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, silicon, and the like.

[0124] In particular, hydrogen contained in the metal oxide reacts with oxygen that bonds with the metal atom to form water, which can cause oxygen vacancies in the metal oxide. When hydrogen enters an oxygen vacancy in the oxide 530, the oxygen vacancy and hydrogen bond to form V. O May form H. V O H functions as a donor and may generate electrons as carriers. Furthermore, some of the hydrogen may bond with oxygen, which is bonded to a metal atom, to generate electrons as carriers. Therefore, a transistor using a metal oxide containing a large amount of hydrogen is likely to have normally-on characteristics. Furthermore, since hydrogen in a metal oxide is easily moved by stresses such as heat and an electric field, the reliability of the transistor may be reduced if the metal oxide contains a large amount of hydrogen. In one embodiment of the present invention, V in the oxide 530 O It is preferable to reduce H as much as possible to obtain high-purity intrinsic or substantially high-purity intrinsic V. O To obtain a metal oxide with a sufficiently reduced amount of H, it is important to remove impurities such as water and hydrogen from the metal oxide (sometimes referred to as dehydration or dehydrogenation treatment), and to supply oxygen to the metal oxide to compensate for oxygen deficiencies (sometimes referred to as oxygen addition treatment). O By using a metal oxide in which impurities such as H are sufficiently reduced for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0125] Defects in which hydrogen has entered oxygen vacancies can function as donors in metal oxides. However, it is difficult to quantitatively evaluate such defects. Therefore, metal oxides are sometimes evaluated using carrier concentration rather than donor concentration. Therefore, in this specification and the like, the carrier concentration assuming a state in which no electric field is applied may be used as a parameter of metal oxides, rather than donor concentration. In other words, the "carrier concentration" described in this specification and the like may sometimes be rephrased as "donor concentration."

[0126] Therefore, when a metal oxide is used for the oxide 530, it is preferable that the hydrogen in the metal oxide is reduced as much as possible. Specifically, in the metal oxide, the hydrogen concentration obtained by secondary ion mass spectrometry (SIMS) is set to 1×10 20 atoms / cm 3 Less than 1 x 10 19 atoms / cm 3 less than 5 × 10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 By using a metal oxide in which impurities such as hydrogen are sufficiently reduced for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0127] When a metal oxide is used for the oxide 530, the carrier concentration of the metal oxide in the channel formation region is 1×10 18 cm -3 Preferably, it is 1×10 or less. 17 cm -3 More preferably, it is less than 1×10 16 cm -3 More preferably, it is less than 1×10 13 cm -3 More preferably, it is less than 1×10 12 cm -3 The lower limit of the carrier concentration of the metal oxide in the channel formation region is not particularly limited, but is preferably, for example, 1×10 -9 cm -3 It can be said that:

[0128] Furthermore, when a metal oxide is used for the oxide 530, contact between the conductor 542 (conductor 542a and conductor 542b) and the oxide 530 may cause oxygen in the oxide 530 to diffuse into the conductor 542, resulting in the oxidation of the conductor 542. The oxidation of the conductor 542 is likely to result in a decrease in the conductivity of the conductor 542. The diffusion of oxygen in the oxide 530 into the conductor 542 can be rephrased as the conductor 542 absorbing the oxygen in the oxide 530.

[0129] Furthermore, oxygen in the oxide 530 may diffuse into the conductor 542 (conductor 542a and conductor 542b), forming a heterogeneous layer between the conductor 542a and the oxide 530b and between the conductor 542b and the oxide 530b. Since the heterogeneous layer contains more oxygen than the conductor 542, the heterogeneous layer is presumed to have insulating properties. In this case, the three-layer structure of the conductor 542, the heterogeneous layer, and the oxide 530b can be regarded as a three-layer structure consisting of a metal, an insulator, and a semiconductor, and may be referred to as a metal-insulator-semiconductor (MIS) structure or a diode junction structure mainly based on the MIS structure.

[0130] The heterogeneous layer is not limited to being formed between the conductor 542 and the oxide 530b. For example, the heterogeneous layer may be formed between the conductor 542 and the oxide 530c. Alternatively, the heterogeneous layer may be formed between the conductor 542 and the oxide 530b and between the conductor 542 and the oxide 530c.

[0131] The metal oxide that functions as a channel formation region in the oxide 530 preferably has a band gap of 2 eV or more, preferably 2.5 eV or more. By using a metal oxide with a wide band gap, the off-state current of the transistor can be reduced.

[0132] The oxide 530 has the oxide 530a below the oxide 530b, which can prevent impurities from diffusing from structures formed below the oxide 530a to the oxide 530b. Moreover, the oxide 530 has the oxide 530c on the oxide 530b, which can prevent impurities from diffusing from structures formed above the oxide 530c to the oxide 530b.

[0133] The oxide 530 preferably has a stacked structure of multiple oxide layers with different atomic ratios of the metal atoms. Specifically, the atomic ratio of the element M among the constituent elements in the metal oxide used for the oxide 530a is preferably greater than the atomic ratio of the element M among the constituent elements in the metal oxide used for the oxide 530b. The atomic ratio of the element M to In in the metal oxide used for the oxide 530a is preferably greater than the atomic ratio of the element M to In in the metal oxide used for the oxide 530b. The atomic ratio of In to M in the metal oxide used for the oxide 530b is preferably greater than the atomic ratio of In to M in the metal oxide used for the oxide 530a. The oxide 530c can be made of the same metal oxide as that used for the oxide 530a or the oxide 530b.

[0134] Specifically, oxide 530a may be a metal oxide having an atomic ratio of In:Ga:Zn=1:3:4 or 1:1:0.5. Oxide 530b may be a metal oxide having an atomic ratio of In:Ga:Zn=4:2:3 or 1:1:1. Oxide 530c may be a metal oxide having an atomic ratio of In:Ga:Zn=1:3:4, Ga:Zn=2:1, or Ga:Zn=2:5. Specific examples of the oxide 530c having a layered structure include a layered structure of In:Ga:Zn=4:2:3 [atomic ratio] and In:Ga:Zn=1:3:4 [atomic ratio], a layered structure of Ga:Zn=2:1 [atomic ratio] and In:Ga:Zn=4:2:3 [atomic ratio], a layered structure of Ga:Zn=2:5 [atomic ratio] and In:Ga:Zn=4:2:3 [atomic ratio], and a layered structure of gallium oxide and In:Ga:Zn=4:2:3 [atomic ratio].

[0135] The conduction band minimum energy of the oxide 530a and the oxide 530c is preferably higher than that of the oxide 530b. In other words, the electron affinity of the oxide 530a and the oxide 530c is preferably smaller than that of the oxide 530b.

[0136] Here, the energy level of the conduction band minimum changes gradually at the junction between the oxides 530a, 530b, and 530c. In other words, the energy level of the conduction band minimum at the junction between the oxides 530a, 530b, and 530c changes continuously or forms a continuous junction. To achieve this, it is preferable to reduce the defect level density of the mixed layers formed at the interface between the oxides 530a and 530b and at the interface between the oxides 530b and 530c.

[0137] Specifically, the oxides 530a and 530b, and the oxides 530b and 530c, have a common element (main component) other than oxygen, thereby forming a mixed layer with a low density of defect states. For example, when the oxide 530b is an In-Ga-Zn oxide, the oxides 530a and 530c may be made of an In-Ga-Zn oxide, a Ga-Zn oxide, a gallium oxide, or the like.

[0138] At this time, the main carrier path is the oxide 530b. By configuring the oxide 530a and the oxide 530c as described above, the defect state density at the interface between the oxide 530a and the oxide 530b and at the interface between the oxide 530b and the oxide 530c can be reduced. As a result, the influence of interface scattering on carrier conduction is reduced, and the transistor 23 can obtain a high on-state current.

[0139] The semiconductor material that can be used for the oxide 530 is not limited to the above-mentioned metal oxides. A semiconductor material having a band gap (a semiconductor material that is not a zero-gap semiconductor) may also be used for the oxide 530. For example, a semiconductor of a simple element such as silicon, a compound semiconductor such as gallium arsenide, or a layered material that functions as a semiconductor (also referred to as an atomic layer material or a two-dimensional material) is preferably used as the semiconductor material. In particular, a layered material that functions as a semiconductor is preferably used as the semiconductor material.

[0140] In this specification and the like, a layered material is a general term for a group of materials having a layered crystal structure. A layered crystal structure is a structure in which layers formed by covalent bonds or ionic bonds are stacked via bonds weaker than covalent bonds or ionic bonds, such as van der Waals forces. A layered material has high electrical conductivity within a unit layer, that is, high two-dimensional electrical conductivity. By using a material that functions as a semiconductor and has high two-dimensional electrical conductivity in the channel formation region, a transistor with a large on-current can be provided.

[0141] Layered materials include graphene, silicene, and chalcogenides. Chalcogenides are compounds containing chalcogen. Chalcogen is a general term for elements in Group 16, including oxygen, sulfur, selenium, tellurium, polonium, and livermorium. Chalcogenides also include transition metal chalcogenides and Group 13 chalcogenides.

[0142] It is preferable to use, for example, a transition metal chalcogenide that functions as a semiconductor as the oxide 530. Specific examples of transition metal chalcogenides that can be used as the oxide 530 include molybdenum sulfide (typically MoS2), molybdenum selenide (typically MoSe2), molybdenum tellurium (typically MoTe2), tungsten sulfide (typically WS2), tungsten selenide (typically WSe2), tungsten tellurium (typically WTe2), hafnium sulfide (typically HfS2), hafnium selenide (typically HfSe2), zirconium sulfide (typically ZrS2), and zirconium selenide (typically ZrSe2).

[0143] Conductors 542a and 542b, which function as a source electrode and a drain electrode, are provided on oxide 530b. Conductors 542a and 542b are preferably made of a metal element selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum, or an alloy containing any of the above metal elements or an alloy combining any of the above metal elements. For example, tantalum nitride, titanium nitride, tungsten, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, or an oxide containing lanthanum and nickel is preferably used. In addition, tantalum nitride, titanium nitride, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are preferred because they are conductive materials that are resistant to oxidation or materials that maintain conductivity even when absorbing oxygen. Furthermore, metal nitride films such as tantalum nitride are preferred because they have barrier properties against hydrogen or oxygen.

[0144] 11A and 11B, the conductor 542a and the conductor 542b are shown as single-layer structures, but they may also have a stacked structure of two or more layers. For example, a tantalum nitride film and a tungsten film may be stacked. Alternatively, a titanium film and an aluminum film may be stacked. Alternatively, a two-layer structure in which an aluminum film is stacked on a tungsten film, a two-layer structure in which a copper film is stacked on a copper-magnesium-aluminum alloy film, a two-layer structure in which a copper film is stacked on a titanium film, or a two-layer structure in which a copper film is stacked on a tungsten film may be used.

[0145] Further, there are three-layer structures in which a titanium film or titanium nitride film is laminated on the titanium film or titanium nitride film, an aluminum film or copper film is laminated on the titanium film or titanium nitride film, and a titanium film or titanium nitride film is further formed thereon, a three-layer structure in which a molybdenum film or molybdenum nitride film is laminated on the molybdenum film or molybdenum nitride film, an aluminum film or copper film is laminated on the molybdenum film or molybdenum nitride film, and a molybdenum film or molybdenum nitride film is further formed thereon, etc. Note that a transparent conductive material containing indium oxide, tin oxide, or zinc oxide may also be used.

[0146] 11A, regions 543a and 543b may be formed as low-resistance regions at and near the interface of the oxide 530 with the conductor 542a (conductor 542b). In this case, the region 543a functions as one of the source region and the drain region, and the region 543b functions as the other of the source region and the drain region. A channel formation region is formed in the region sandwiched between the regions 543a and 543b.

[0147] By providing the conductor 542a (conductor 542b) so as to be in contact with the oxide 530, the oxygen concentration in the region 543a (region 543b) may be reduced. Also, a metal compound layer containing the metal contained in the conductor 542a (conductor 542b) and components of the oxide 530 may be formed in the region 543a (region 543b). In such a case, the carrier concentration in the region 543a (region 543b) increases, and the region 543a (region 543b) becomes a low-resistance region.

[0148] The insulator 544 is provided to cover the conductors 542a and 542b and suppresses oxidation of the conductors 542a and 542b. In this case, the insulator 544 may be provided to cover the side surface of the oxide 530 and to be in contact with the insulator 524.

[0149] The insulator 544 can be a metal oxide containing one or more elements selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, neodymium, lanthanum, magnesium, etc. Alternatively, the insulator 544 can be silicon nitride oxide, silicon nitride, or the like.

[0150] In particular, it is preferable to use, as the insulator 544, an insulator containing an oxide of either or both of aluminum and hafnium, such as aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate). In particular, hafnium aluminate has higher heat resistance than a hafnium oxide film. Therefore, it is preferable because it is less likely to crystallize during heat treatment in a later process. Note that the insulator 544 is not an essential component if the conductors 542a and 542b are made of oxidation-resistant materials or if their conductivity does not decrease significantly even when they absorb oxygen. The insulator 544 may be designed appropriately depending on the desired transistor characteristics.

[0151] The insulator 544 can prevent impurities such as water and hydrogen contained in the insulator 580 from diffusing to the oxide 530b through the oxide 530c and the insulator 550. The insulator 544 can also prevent the conductor 560 from being oxidized by excess oxygen contained in the insulator 580.

[0152] The insulator 550 functions as a first gate insulating film. The insulator 550 is preferably arranged to be in contact with the inside (top surface and side surface) of the oxide 530c. Like the insulator 524 described above, the insulator 550 is preferably formed using an insulator that contains excess oxygen and releases oxygen by heating.

[0153] Specifically, silicon oxide having excess oxygen, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, and silicon oxide having vacancies can be used. In particular, silicon oxide and silicon oxynitride are preferable because they are stable against heat.

[0154] By providing the insulator 550, which releases oxygen upon heating, in contact with the top surface of the oxide 530c, oxygen can be effectively supplied from the insulator 550 to the channel formation region of the oxide 530b through the oxide 530c. Similar to the insulator 524, the concentration of impurities such as water or hydrogen in the insulator 550 is preferably reduced. The thickness of the insulator 550 is preferably 1 nm to 20 nm.

[0155] Furthermore, a metal oxide may be provided between the insulator 550 and the conductor 560 to efficiently supply excess oxygen contained in the insulator 550 to the oxide 530. The metal oxide preferably has a function of suppressing oxygen diffusion from the insulator 550 to the conductor 560. By providing a metal oxide having a function of suppressing oxygen diffusion, the diffusion of excess oxygen from the insulator 550 to the conductor 560 is suppressed. In other words, a decrease in the amount of excess oxygen supplied to the oxide 530 can be suppressed. Furthermore, oxidation of the conductor 560 due to excess oxygen can be suppressed. As the metal oxide, a material that can be used for the insulator 544 may be used.

[0156] The insulator 550 may have a stacked structure, similar to the second gate insulating film. As transistors become smaller and more highly integrated, thinner gate insulating films can cause problems such as leakage current. Therefore, by using a stacked structure of a high-k material and a thermally stable material for the insulator that functions as the gate insulating film, it becomes possible to reduce the gate potential during transistor operation while maintaining the physical film thickness. Furthermore, a stacked structure that is thermally stable and has a high dielectric constant can be achieved.

[0157] The conductor 560 functioning as the first gate electrode is shown as a two-layer structure in FIGS. 11A and 11B, but may be a single-layer structure or a stacked structure of three or more layers.

[0158] The conductor 560a is preferably made of a conductive material that suppresses the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (NO, NO, NO, etc.), and copper atoms. Alternatively, a conductive material that suppresses the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.) is preferably used. The conductor 560a has the function of suppressing the diffusion of oxygen, which can suppress the oxidation of the conductor 560b due to oxygen contained in the insulator 550 and a decrease in conductivity. Examples of conductive materials that suppress the diffusion of oxygen include tantalum, tantalum nitride, ruthenium, and ruthenium oxide. Alternatively, the conductor 560a can be made of an oxide semiconductor that can be used for the oxide 530. In this case, the conductor 560b can be formed by sputtering to reduce the electrical resistance of the conductor 560a, thereby making it a conductor. This can be referred to as an OC (Oxide Conductor) electrode.

[0159] The conductor 560b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. Since the conductor 560b also functions as wiring, it is preferable to use a conductor with high conductivity. For example, a conductive material containing tungsten, copper, or aluminum as a main component can be used. The conductor 560b may have a layered structure, such as a layered structure of titanium or titanium nitride and the above-mentioned conductive material.

[0160] The insulator 580 is provided over the conductor 542a and the conductor 542b with the insulator 544 interposed 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 doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, silicon oxide having voids, or a resin. Silicon oxide and silicon oxynitride are particularly preferred because they are thermally stable. Silicon oxide and silicon oxide having voids are particularly preferred because they allow for easy formation of excess oxygen regions in a later step.

[0161] The insulator 580 preferably has an excess oxygen region. By providing the insulator 580, from which oxygen is released by heating, with a region in contact with the oxide 530c, oxygen in the insulator 580 can be efficiently supplied to the oxide 530a and the oxide 530b through the oxide 530c. Note that the concentration of impurities such as water and hydrogen in the insulator 580 is preferably reduced.

[0162] The opening of the insulator 580 is formed to overlap the region between the conductor 542a and the conductor 542b, so that the conductor 560 is formed so as to be embedded in the opening of the insulator 580 and the region sandwiched between the conductor 542a and the conductor 542b.

[0163] When miniaturizing semiconductor devices, it is necessary to shorten the gate length, but it is also necessary to prevent the conductivity of the conductor 560 from decreasing. If the film thickness of the conductor 560 is increased to achieve this, the conductor 560 may have a shape with a high aspect ratio. In this embodiment, the conductor 560 is provided so as to be embedded in the opening of the insulator 580. Therefore, even if the conductor 560 has a shape with a high aspect ratio, the conductor 560 can be formed without collapsing during the process.

[0164] The insulator 574 is preferably provided in contact 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 a sputtering method, excess oxygen regions can be provided in the insulator 550 and the insulator 580. This allows oxygen to be supplied from the excess oxygen regions into the oxide 530.

[0165] For example, the insulator 574 can be a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, and the like.

[0166] In particular, aluminum oxide has high barrier properties and can suppress the diffusion of hydrogen and nitrogen even when it is a thin film with a thickness of 0.5 nm to 3.0 nm. Therefore, aluminum oxide formed by sputtering can function as both an oxygen source and a barrier film against impurities such as hydrogen.

[0167] An insulator 581 functioning as an interlayer film is preferably provided over the insulator 574. Like the insulator 524 and the like, the insulator 581 preferably has a reduced concentration of impurities such as water or hydrogen.

[0168] Furthermore, the conductor 540a and the conductor 540b are placed in openings formed in the insulator 581, the insulator 574, the insulator 580, and the insulator 544. The conductor 540a and the conductor 540b are provided opposite each other with the conductor 560 interposed therebetween. The conductor 540a and the conductor 540b have the same structure as the conductor 546 and the conductor 548, which will be described later.

[0169] An insulator 582 is provided over the insulator 581. The insulator 582 is preferably formed using a substance that has a barrier property against oxygen and hydrogen. Therefore, the insulator 582 can be formed using a material similar to that of the insulator 514. For example, the insulator 582 is preferably formed using a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

[0170] In particular, aluminum oxide has a high blocking effect of preventing the permeation of both oxygen and impurities such as hydrogen and moisture, which can cause fluctuations in the electrical characteristics of a transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen and moisture from entering the transistor 23 during and after the transistor manufacturing process. Furthermore, aluminum oxide can suppress the release of oxygen from the oxide that constitutes the transistor 23. Therefore, aluminum oxide is suitable for use as a protective film for the transistor 23.

[0171] An insulator 586 is provided over the insulator 582. The insulator 586 can be formed using a material similar to that of the insulator 320. By using a material with a relatively low dielectric constant for these insulators, parasitic capacitance between wirings can be reduced. For example, a silicon oxide film, a silicon oxynitride film, or the like can be used as the insulator 586.

[0172] Furthermore, conductors 546, conductors 548, etc. are embedded in insulators 520, 522, 524, 544, 580, 574, 581, 582, and 586.

[0173] The conductor 546 and the conductor 548 function as plugs or wirings that connect the silicon substrate 12 and the transistor 23. The conductor 546 and the conductor 548 can be formed using a material similar to that of the conductor 328 or the conductor 330.

[0174] After the transistor 23 is formed, an opening may be formed to surround the transistor 23, and an insulator with high barrier properties against hydrogen or water may be formed to cover the opening. By surrounding the transistor 23 with the insulator with high barrier properties, it is possible to prevent moisture and hydrogen from entering from the outside. Alternatively, multiple transistors 23 may be collectively surrounded by an insulator with high barrier properties against hydrogen or water. When forming an opening to surround the transistor 23, for example, it is preferable to form an opening that reaches the insulator 514 or the insulator 522 and form the insulator with high barrier properties in contact with the insulator 514 or the insulator 522, because this can serve as part of the manufacturing process of the transistor 23. As the insulator with high barrier properties against hydrogen or water, for example, a material similar to that of the insulator 522 may be used.

[0175] Next, the conductor 22 and the conductor 21 are provided. The conductor 22 and the conductor 21 function as plugs or wirings that connect the silicon substrate 12 and the transistor 23.

[0176] A metal film containing an element selected from molybdenum, titanium, tantalum, tungsten, aluminum, copper, chromium, neodymium, and scandium, or a metal nitride film containing any of the above elements (tantalum nitride film, titanium nitride film, molybdenum nitride film, tungsten nitride film), etc. can be used for the conductors 21 and 22. Alternatively, a conductive material 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, or indium tin oxide with silicon oxide added can also be used.

[0177] 10, the conductor 21 and the conductor 22 are shown as having a single layer structure, but are not limited to this configuration and may have a laminated structure of two or more layers. For example, a conductor having a barrier property and a conductor having high adhesion to the conductor having high conductivity may be formed between a conductor having a barrier property and a conductor having high conductivity.

[0178] By using this structure, miniaturization or high integration can be achieved in a semiconductor device including a transistor including an oxide semiconductor.

[0179] 12A and 12B illustrate modifications of the transistor 23 illustrated in FIGS. 11A and 11B. FIG. 12A is a cross-sectional view of the transistor 23 in the channel length direction, and FIG. 12B is a cross-sectional view of the transistor 23 in the channel width direction. Note that the structures illustrated in FIGS. 12A and 12B can also be applied to other transistors, such as the transistor 23, included in the semiconductor device of one embodiment of the present invention.

[0180] 12A and 12B differs from the transistor 23 shown in FIGS. 11A and 11B in that it includes an insulator 402 and an insulator 404. It also differs from the transistor 23 shown in FIGS. 11A and 11B in that an insulator 552 is provided in contact with a side surface of the conductor 540a and an insulator 552 is provided in contact with a side surface of the conductor 540b. It also differs from the transistor 23 shown in FIGS. 11A and 11B in that it does not include the insulator 520.

[0181] 12A and 12B, the insulator 402 is provided over the insulator 512. The insulator 404 is provided over the insulator 574 and the insulator 402.

[0182] 12A and 12B , the insulators 514, 516, 522, 524, 544, 580, and 574 are patterned, and the insulator 404 covers them. That is, the insulator 404 is in contact with the top surface of the insulator 574, the side surface of the insulator 574, the side surface of the insulator 580, the side surface of the insulator 544, the side surface of the insulator 524, the side surface of the insulator 522, the side surface of the insulator 516, the side surface of the insulator 514, and the top surface of the insulator 402. As a result, the oxide 530 and the like are isolated from the outside by the insulators 404 and 402.

[0183] The insulators 402 and 404 preferably have a high function of suppressing diffusion of hydrogen (for example, at least one of a hydrogen atom and a hydrogen molecule) or water molecules. For example, silicon nitride or silicon nitride oxide, which are materials with high hydrogen barrier properties, are preferably used for the insulators 402 and 404. This can suppress diffusion of hydrogen and the like into the oxide 530, thereby suppressing deterioration in the characteristics of the transistor 23. Therefore, the reliability of the semiconductor device of one embodiment of the present invention can be improved.

[0184] The insulator 552 is provided in contact with the insulator 581, the insulator 404, the insulator 574, the insulator 580, and the insulator 544. The insulator 552 preferably has a function of suppressing diffusion of hydrogen or water molecules. For example, the insulator 552 is preferably formed using an insulator with high hydrogen barrier properties, such as silicon nitride, aluminum oxide, or silicon nitride oxide. Silicon nitride is particularly suitable for use as the insulator 552 because it has high hydrogen barrier properties. Using a material with high hydrogen barrier properties for the insulator 552 can suppress diffusion of impurities such as water or hydrogen from the insulator 580 or the like to the oxide 530 through the conductors 540a and 540b. Furthermore, oxygen contained in the insulator 580 can be prevented from being absorbed by the conductors 540a and 540b. Thus, the reliability of the semiconductor device of one embodiment of the present invention can be improved.

[0185] 13A and 13B illustrate modifications of the transistor illustrated in FIGS. 12A and 12B. FIG. 13A is a cross-sectional view of the transistor in the channel length direction, and FIG. 13B is a cross-sectional view of the transistor in the channel width direction. The transistor illustrated in FIGS. 13A and 13B differs from the transistor illustrated in FIGS. 12A and 12B in that the oxide 530c has a two-layer structure of oxides 530c1 and 530c2.

[0186] The oxide 530c1 contacts the top surface of the insulator 524, the side surface of the oxide 530a, the top surface and side surface of the oxide 530b, the side surfaces of the conductors 542a and 542b, the side surface of the insulator 544, and the side surface of the insulator 580. The oxide 530c2 contacts the insulator 550.

[0187] Oxide 530c1 can be, for example, an In-Zn oxide. Oxide 530c2 can be made of the same material as that used for oxide 530c when oxide 530c has a single-layer structure. For example, oxide 530c2 can be made of a metal oxide with an atomic ratio of n:Ga:Zn=1:3:4, Ga:Zn=2:1, or Ga:Zn=2:5.

[0188] By forming the oxide 530c as a two-layer structure of the oxide 530c1 and the oxide 530c2, the on-state current of the transistor can be increased compared to when the oxide 530c has a single-layer structure. Therefore, the transistor can be, for example, a power MOS transistor. The oxide 530c of the transistor shown in FIGS. 11A and 11B can also have a two-layer structure of the oxide 530c1 and the oxide 530c2.

[0189] 13A and 13B can be applied to, for example, the transistor 23 to increase the on-state current of the transistor 23. In the transistors shown in FIGS.

[0190] This embodiment mode can be implemented in appropriate combination with the structures described in other embodiment modes or the like.

[0191] (Embodiment 3) This embodiment describes the structures of CAC-OS and CAAC-OS, which are metal oxides that can be used for the OS transistors described in the above embodiments. Note that in this specification and the like, CAC represents an example of a function or material structure, and CAAC represents an example of a crystal structure.

[0192] <Metal oxide composition> A CAC-OS or CAC-metal oxide has a conductive function in a part of the material and an insulating function in a part of the material, and functions as a semiconductor as a whole. When a CAC-OS or CAC-metal oxide is used in the active layer of a transistor, the conductive function is a function of allowing electrons (or holes) to flow as carriers, and the insulating function is a function of preventing the flow of electrons as carriers. By making the conductive function and the insulating function act complementarily, a switching function (on / off function) can be imparted to the CAC-OS or CAC-metal oxide. By separating the respective functions in the CAC-OS or CAC-metal oxide, both functions can be maximized.

[0193] Furthermore, CAC-OS or CAC-metal oxide has conductive regions and insulating regions. The conductive regions have the above-mentioned conductive function, and the insulating regions have the above-mentioned insulating function. In addition, the conductive regions and the insulating regions may be separated at the nanoparticle level in the material. In addition, the conductive regions and the insulating regions may be unevenly distributed in the material. In addition, the conductive regions may be observed as connected in a cloud-like shape with the periphery blurred.

[0194] In addition, in CAC-OS or CAC-metal oxide, the conductive regions and the insulating regions may be dispersed in the material with sizes of 0.5 nm to 10 nm, preferably 0.5 nm to 3 nm.

[0195] Furthermore, the CAC-OS or CAC-metal oxide is composed of components with different band gaps. For example, the CAC-OS or CAC-metal oxide is composed of a component with a wide gap due to an insulating region and a component with a narrow gap due to a conductive region. In this configuration, when carriers flow, the carriers mainly flow in the component with the narrow gap. Furthermore, the component with the narrow gap acts complementarily with the component with the wide gap, and carriers also flow in the component with the wide gap in conjunction with the component with the narrow gap. Therefore, when the CAC-OS or CAC-metal oxide is used in the channel formation region of a transistor, the transistor can achieve high current driving power in the on state, i.e., a large on-state current, and high field-effect mobility.

[0196] That is, CAC-OS or CAC-metal oxide can also be called a matrix composite or a metal matrix composite.

[0197] <Metal oxide structure> Oxide semiconductors are classified into single-crystal oxide semiconductors and non-single-crystal oxide semiconductors, such as CAAC-OS, polycrystalline oxide semiconductors, nanocrystalline oxide semiconductors (nc-OS), amorphous-like oxide semiconductors (a-like OS), and amorphous oxide semiconductors.

[0198] CAAC-OS has a c-axis orientation and a distorted crystal structure in which multiple nanocrystals are connected in the ab-plane direction. The distorted crystal structure refers to the change in the lattice orientation between regions with a uniform lattice arrangement and regions with a different uniform lattice arrangement in the regions where multiple nanocrystals are connected.

[0199] Nanocrystals are basically hexagonal, but not necessarily regular hexagonal, and may have non-regular hexagonal shapes. The strain may also result in pentagonal, heptagonal, or other lattice arrangements. In CAAC-OS, no clear grain boundaries are observed even near the strain. This indicates that the formation of grain boundaries is suppressed by the strained lattice arrangement. This is thought to be because the CAAC-OS can tolerate strain due to the lack of close-packed oxygen atom arrangement in the ab-plane direction and the change in interatomic bond distance caused by the substitution of metal elements.

[0200] CAAC-OS also tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium and oxygen (hereinafter referred to as an In layer) and a layer containing the element M, zinc, and oxygen (hereinafter referred to as an (M,Zn) layer) are stacked. Note that indium and the element M are mutually substituted, and when the element M in an (M,Zn) layer is substituted with indium, the layer can also be referred to as an (In,M,Zn) layer. When the indium in an In layer is substituted with the element M, the layer can also be referred to as an (In,M) layer.

[0201] CAAC-OS is an oxide semiconductor with high crystallinity. On the other hand, because no clear grain boundaries are observed in CAAC-OS, it can be said that a decrease in electron mobility due to grain boundaries is unlikely to occur. Furthermore, because the crystallinity of oxide semiconductors can be reduced by the inclusion of impurities or the generation of defects, CAAC-OS can also be said to be an oxide semiconductor with few impurities or defects (such as oxygen vacancies). Therefore, oxide semiconductors with CAAC-OS have stable physical properties. Therefore, oxide semiconductors with CAAC-OS are heat-resistant and highly reliable. Furthermore, CAAC-OS is stable even under high temperatures (so-called thermal budgets) during the manufacturing process. Therefore, using CAAC-OS for OS transistors can increase the flexibility of the manufacturing process.

[0202] The nc-OS has periodic atomic arrangement in a small region (for example, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). Furthermore, the nc-OS exhibits no regularity in the crystal orientation between different nanocrystals. Therefore, no orientation is observed throughout the film. Therefore, depending on the analytical method, the nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor.

[0203] The a-like OS is an oxide semiconductor having a structure between the nc-OS and the amorphous oxide semiconductor. The a-like OS has a pore or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and the CAAC-OS.

[0204] Oxide semiconductors have a variety of structures, each with different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, an nc-OS, and a CAAC-OS.

[0205] <Transistors containing oxide semiconductors> Next, a case where the oxide semiconductor is used in a transistor will be described.

[0206] By using the oxide semiconductor for a transistor, a transistor with high field-effect mobility and high reliability can be realized.

[0207] In addition, it is preferable to use an oxide semiconductor with a low carrier concentration for the transistor. In order to reduce the carrier concentration of the oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be reduced to reduce the density of defect states. In this specification and the like, a semiconductor having a low impurity concentration and a low density of defect states is referred to as a highly purified intrinsic semiconductor or a substantially highly purified intrinsic semiconductor.

[0208] Furthermore, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low density of defect states, and therefore the density of trap states may also be low.

[0209] Furthermore, charges trapped in the trap states of an oxide semiconductor take a long time to disappear and may behave like fixed charges. Therefore, a transistor in which a channel formation region is formed in an oxide semiconductor with a high density of trap states may have unstable electrical characteristics.

[0210] Therefore, in order to stabilize the electrical characteristics of a transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. Furthermore, in order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in the adjacent film. Examples of impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, and silicon.

[0211] <Impurities> Here, the influence of each impurity in an oxide semiconductor will be described.

[0212] When an oxide semiconductor contains silicon or carbon, which is one of the Group 14 elements, defect levels are formed in the oxide semiconductor. Therefore, the concentrations of silicon or carbon in the oxide semiconductor and those near the interface with the oxide semiconductor (concentrations obtained by secondary ion mass spectrometry (SIMS)) are calculated as follows: 18 atoms / cm 3 Less than or equal to 2 x 10 17 atoms / cm 3 The following applies.

[0213] Furthermore, when an oxide semiconductor contains an alkali metal or alkaline earth metal, defect states may be formed and carriers may be generated. Therefore, a transistor using an oxide semiconductor containing an alkali metal or alkaline earth metal is likely to have normally-on characteristics. For this reason, it is preferable to reduce the concentration of the alkali metal or alkaline earth metal in the oxide semiconductor. Specifically, the concentration of the alkali metal or alkaline earth metal in the oxide semiconductor obtained by SIMS is preferably reduced to 1×10 18 atoms / cm3 Less than or equal to 2 x 10 16 atoms / cm 3 Do the following:

[0214] Furthermore, when nitrogen is contained in an oxide semiconductor, electrons serving as carriers are generated, the carrier concentration increases, and the oxide semiconductor is likely to become n-type. As a result, a transistor using an oxide semiconductor containing nitrogen as a semiconductor tends to have normally-on characteristics. Therefore, it is preferable that the nitrogen content in the oxide semiconductor be reduced as much as possible. For example, the nitrogen concentration in the oxide semiconductor is less than 5×10 by SIMS. 19 atoms / cm 3 Less than 5 x 10 18 atoms / cm 3 Less than 1×10, more preferably 18 atoms / cm 3 Less than 5 × 10, more preferably 17 atoms / cm 3 The following applies.

[0215] Furthermore, hydrogen contained in an oxide semiconductor may react with oxygen bonded to a metal atom to form water, forming an oxygen vacancy. When hydrogen enters the oxygen vacancy, electrons serving as carriers may be generated. Furthermore, some of the hydrogen may bond with oxygen bonded to a metal atom to generate electrons serving as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen is likely to have normally-on characteristics. For this reason, it is preferable to reduce the amount of hydrogen in the oxide semiconductor as much as possible. Specifically, when the hydrogen concentration in an oxide semiconductor obtained by SIMS is 1×10 20 atoms / cm 3 Less than 1 x 10 19 atoms / cm 3 less than 5 × 10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 Less than.

[0216] When an oxide semiconductor with sufficiently reduced impurities is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0217] This embodiment mode can be implemented in appropriate combination with the structures described in other embodiment modes or the like.

[0218] (Fourth embodiment) In this embodiment mode, examples of electronic devices in which the semiconductor device or the like described in the above embodiment modes is incorporated will be described with reference to FIGS.

[0219] The robot 7100 includes an illuminance sensor, a microphone, a camera, a speaker, a display, various sensors (infrared sensor, ultrasonic sensor, acceleration sensor, piezoelectric sensor, optical sensor, gyro sensor, etc.), a movement mechanism, etc. The electronic component 100A or 100D functions as a switch for controlling the power supply for driving these peripheral devices.

[0220] The microphone has a function of detecting acoustic signals such as the user's voice and environmental sounds. The speaker has a function of emitting audio signals such as voice and warning sounds. The robot 7100 can analyze the audio signals input via the microphone and emit the necessary audio signals from the speaker. The robot 7100 can communicate with the user using the microphone and speaker.

[0221] The camera has a function of capturing images of the surroundings of the robot 7100. The robot 7100 also has a function of moving using a movement mechanism. The robot 7100 can capture images of the surroundings using the camera and analyze the images to detect the presence or absence of obstacles when moving.

[0222] Air vehicle 7120 has a propeller, a camera, a battery, etc., and has the function of flying autonomously. Electronic component 100A or 100D functions as a switch for controlling the power supply for driving these peripheral devices.

[0223] The cleaning robot 7140 has a display on its top surface, multiple cameras on its sides, a brush, operation buttons, various sensors, and the like. The electronic component 100A or 100D functions as a switch for controlling the power supply for driving these peripheral devices. Although not shown, the cleaning robot 7140 is equipped with tires, a suction port, and the like. The cleaning robot 7140 can move on its own, detect dirt, and suck up the dirt through a suction port provided on its bottom surface.

[0224] The automobile 7160 has an engine, tires, brakes, a steering device, a camera, etc. The electronic component 100A or 100D functions as a switch for controlling the power supply for driving these peripheral devices.

[0225] The electronic component 100A or 100D can be incorporated into a TV device 7200 (television receiver), a smartphone 7210, a PC (personal computer) 7220, 7230, a game console 7240, a game console 7260, or the like.

[0226] For example, the electronic component 100A or 100D built into the TV device 7200 functions as a switch for controlling the power supply for driving the TV device 7200.

[0227] The smartphone 7210 is an example of a portable information terminal. The smartphone 7210 includes a microphone, a camera, a speaker, various sensors, and a display. The electronic component 100A or 100D functions as a switch for controlling the power supply for driving these peripheral devices.

[0228] PC 7220 and PC 7230 are examples of a notebook PC and a desktop PC, respectively. A keyboard 7232 and a monitor device 7233 can be connected to PC 7230 wirelessly or via a wired connection. Game console 7240 is an example of a portable game console. Game console 7260 is an example of a desktop game console. A controller 7262 is connected to game console 7260 wirelessly or via a wired connection. Electronic component 100A or 100D functions as a switch for controlling the power supply for driving each component.

[0229] This embodiment mode can be implemented in appropriate combination with any of the structures described in other embodiment modes.

[0230] (Notes regarding the present specification) The above-described embodiments and the respective components in the embodiments will be described below with additional notes.

[0231] The configurations shown in each embodiment can be combined as appropriate with configurations shown in other embodiments or examples to form one aspect of the present invention. Furthermore, when multiple configuration examples are shown in one embodiment, the configuration examples can be combined as appropriate.

[0232] In addition, the content (or even a part of the content) described in one embodiment can be applied to, combined with, or replaced with another content (or even a part of the content) described in that embodiment, and / or with the content (or even a part of the content) described in one or more other embodiments.

[0233] The contents described in the embodiments refer to the contents described in each embodiment using various figures or the contents described using text in the specification.

[0234] Furthermore, a figure (or even a part thereof) described in one embodiment can be combined with another part of that figure, another figure (or even a part thereof) described in that embodiment, and / or a figure (or even a part thereof) described in one or more other embodiments to form even more figures.

[0235] In addition, in the present specification and the like, in the block diagrams, components are classified by function and shown as independent blocks. However, in actual circuits, etc., it is difficult to separate components by function, and there may be cases where one circuit is involved in multiple functions, or where one function is involved across multiple circuits. Therefore, the blocks in the block diagrams are not limited to the components described in the specification, but may be rephrased appropriately depending on the situation.

[0236] In addition, in the drawings, the size, layer thickness, or region is shown at an arbitrary size for convenience of explanation. Therefore, it is not necessarily limited to the scale. Note that the drawings are shown schematically for clarity, and are not limited to the shapes or values ​​shown in the drawings. For example, it is possible to include variations in signal, voltage, or current due to noise, or variations in signal, voltage, or current due to timing deviations.

[0237] Furthermore, the positional relationships of components shown in the drawings are relative. Therefore, when describing components with reference to the drawings, terms such as "above" and "below" indicating the positional relationships may be used for convenience. The positional relationships of components are not limited to the content described in this specification, and can be rephrased appropriately depending on the situation.

[0238] In this specification and the like, when describing the connection relationship of a transistor, the term "one of the source or drain" (or first electrode or first terminal) is used, and the other of the source and drain is referred to as "the other of the source or drain" (or second electrode or second terminal). This is because the source and drain of a transistor vary depending on the structure or operating conditions of the transistor. Note that the names of the source and drain of a transistor can be appropriately changed to source (drain) terminal, source (drain) electrode, etc. depending on the situation.

[0239] Furthermore, the terms "electrode" and "wiring" used in this specification and elsewhere do not limit the functionality of these components. For example, an "electrode" may be used as part of a "wiring," and vice versa. Furthermore, the terms "electrode" and "wiring" also include cases where multiple "electrodes" or "wirings" are integrally formed.

[0240] Furthermore, in this specification and the like, voltage and potential can be interchanged as appropriate. Voltage refers to the potential difference from a reference potential. For example, if the reference potential is a ground voltage (earth voltage), voltage can be interchanged with potential. Ground potential does not necessarily mean 0 V. Note that potential is relative, and the potential applied to wiring, etc. may change depending on the reference potential.

[0241] In this specification and the like, a node can be referred to as a terminal, a wiring, an electrode, a conductive layer, a conductor, an impurity region, etc. depending on the circuit configuration, device structure, etc. Also, a terminal, a wiring, etc. can be referred to as a node.

[0242] In this specification, "A and B are connected" means that A and B are electrically connected. Here, "A and B are electrically connected" means a connection in which an electrical signal can be transmitted between A and B when an object (such as a switch, transistor element, or diode, or a circuit including such an object and wiring) is present between A and B. Note that "A and B are electrically connected" also includes a case in which A and B are directly connected. Here, "A and B are directly connected" means a connection in which an electrical signal can be transmitted between A and B via wiring (or electrodes) or the like, without passing through the object. In other words, a direct connection means a connection that can be regarded as the same circuit diagram when represented by an equivalent circuit.

[0243] In this specification, a switch refers to a device that has the function of controlling whether a current flows by being in a conductive state (on state) or a non-conductive state (off state), or a device that has the function of selecting and switching a path for a current to flow.

[0244] In this specification, the channel length refers to, for example, in a top view of a transistor, a region where a semiconductor (or a portion in the semiconductor through which current flows when the transistor is on) and a gate overlap, or a distance between a source and a drain in a region where a channel is formed.

[0245] In this specification, the channel width refers to, for example, the length of the region where the semiconductor (or the portion in the semiconductor through which current flows when the transistor is on) and the gate electrode overlap, or the length of the portion where the source and drain face each other in the region where the channel is formed.

[0246] In this specification and the like, terms such as "film" and "layer" can be interchangeable depending on the circumstances. For example, the term "conductive layer" can be changed to the term "conductive film." Or, for example, the term "insulating film" can be changed to the term "insulating layer." [Explanation of symbols]

[0247] 10: semiconductor device, 10A: semiconductor device, 10B: semiconductor device, 10C: semiconductor device, 10D: semiconductor device, 10E: semiconductor device, 11: device, 11A: device, 11B: device, 11C: device, 11D: device, 12: silicon substrate, 20: semiconductor device, 21A: conductor, 21B: conductor, 22A: conductor, 22B: conductor, 23: transistor, 23A: transistor, 23B: transistor, 23B_1: transistor, 23B_2: transistor, 23C: transistor, 23D: transistor, 23R: region, 24A: opening, 24B: opening, 25: transistor, 25A: oxide layer, 25B: oxide layer, 26: transistor, 26A: gate electrode, 26B: gate electrode, 26B_1: conductor, 26B_2: conductor, 27A: region, 27B: region, 28: oxide layer, 29: conductor, 30: electrode layer, 31A: conductor, 31B: conductor, 51A: region, 51B: region, 60: battery protection circuit, 61: battery, 100A: electronic component, 100B: electronic component, 100C: electronic component, 100D: electronic component, 101: substrate, 102: adhesive layer, 103: resin layer, 104A: metal wiring, 104B: metal wiring Wire, 105A: electrode, 105B: electrode, 106: housing, 107: heat sink, 199: power storage device, 320: insulator, 322: insulator, 324: insulator, 326: insulator, 328: conductor, 330: conductor, 350: insulator, 352: insulator, 354: insulator, 356: conductor, 402: insulator, 404: insulator, 503: conductor, 503a: conductor, 503b: conductor, 510: insulator, 512: insulator, 514: insulator, 516: insulator, 518: conductor, 520: insulator, 522: insulator, 524: insulator, 530: oxide, 530a: oxide, 5 30b: oxide, 530c: oxide, 530c1: oxide, 530c2: oxide, 540a: conductor, 540b: conductor, 542: conductor, 542a: conductor, 542b: conductor, 543a: region, 543b: region, 544: insulator, 546: conductor, 548: conductor, 550: insulator, 552: insulator, 560: conductor, 560a: conductor, 560b: conductor, 574: insulator, 580: insulator, 581: insulator, 582: insulator, 586: insulator, 610: conductor, 612: conductor, 7100: robot, 7120: flying object, 7140: cleaning robot,7160: Automobile, 7200: TV device, 7210: Smartphone, 7220: PC, 7230: PC, 7232: Keyboard, 7233: Monitor device, 7240: Game console, 7260: Game console, 7262: Controller,

Claims

1. A silicon substrate; a device disposed above the silicon substrate; an electrode layer disposed over the device; the electrode layer has a first conductor; the device includes a transistor and a second conductor; the transistor includes an oxide semiconductor film, the oxide semiconductor film has a channel formation region of the transistor, The silicon substrate is made conductive, the first conductor is electrically connected to a source of the transistor; the second conductor is electrically connected to the drain of the transistor and to the silicon substrate through an opening in the device; the second conductor has a region in contact with a lower surface of the oxide semiconductor film.

2. A silicon substrate; a device disposed above the silicon substrate; an electrode layer disposed over the device; the electrode layer has a first conductor; the device comprises a first transistor, a second transistor, a second conductor, and a third conductor; the first transistor includes a first oxide semiconductor film; the first oxide semiconductor film has a channel formation region of the first transistor, the second transistor includes a second oxide semiconductor film; the second oxide semiconductor film has a channel formation region of the second transistor, The silicon substrate is made conductive, the first conductor is electrically connected to a source of the first transistor and a source of the second transistor; the second conductor is electrically connected to a drain of the first transistor and to the silicon substrate through a first opening in the device; the third conductor is electrically connected to the drain of the second transistor and to the silicon substrate through a second opening in the device; the second conductor has a region in contact with a lower surface of the first oxide semiconductor film, the third conductor has a region in contact with a lower surface of the second oxide semiconductor film.

3. In claim 1 or claim 2, The semiconductor device, wherein the silicon substrate is imparted with p-type conductivity.

4. In any one of claims 1 to 3, the silicon substrate and the device are covered with a resin layer; The resin layer is provided inside a housing of the semiconductor device.

5. In any one of claims 1 to 4, The semiconductor device further comprises a heat sink provided on the silicon substrate via an insulating layer.

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