Semiconductor Devices

Abstract

To provide a semiconductor device with a novel structure, being excellent in consumption power reduction and operation reliability.SOLUTION: A semiconductor device 100 includes a current voltage conversion unit 101, a current switch unit 102, a voltage current conversion unit 103, and a control unit. The current switch unit 102 includes a first transistor 111. The voltage current conversion unit 103 includes a second transistor 121. The control unit includes a third transistor. The first transistor 111 includes an oxide semiconductor layer 112 in a channel formation region. The second transistor 121 includes a nitride semiconductor layer 122 in the channel formation region. The third transistor contains silicon in the channel formation region. The first transistor 111 is provided on the first substrate. The second transistor 121 and the third transistor are provided on a second substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Note that one aspect of the present invention is not limited to the above-mentioned technical fields. The technical fields of the inventions disclosed in this specification relate to products, methods, or manufacturing methods. Alternatively, one aspect of the present invention relates to processes, machines, manufactures, or compositions of matter.

[0003] In this specification and the like, a semiconductor device generally refers to anything that can function by utilizing semiconductor characteristics. Therefore, semiconductor elements such as transistors and diodes, and circuits including semiconductor elements are semiconductor devices. Furthermore, display devices, light-emitting devices, lighting devices, electro-optical devices, imaging devices, communication devices, and electronic devices may include semiconductor elements and semiconductor circuits. Therefore, display devices, light-emitting devices, lighting devices, electro-optical devices, imaging devices, communication devices, and electronic devices may also be called semiconductor devices. [Background technology]

[0004] High-mobility transistors, such as those made of gallium nitride, are used as switching devices for high-speed operation. Transistors that have nitrides of group 13 elements, such as gallium nitride (GaN), in the channel formation region (hereinafter referred to as GaN transistors) operate in depletion mode (normally on).

[0005] To improve performance, it is desirable to combine GaN transistors with transistors containing different semiconductor materials, such as transistors having silicon (Si) in the channel formation region (Si transistors). For example, Patent Document 1 discloses a switching device that can operate in enhancement mode (normally off) by combining a depletion mode GaN transistor with a Si transistor. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-222360 Summary of the Invention [Problem to be solved by the invention]

[0007] As communication speeds increase, the switching speed of switching devices also needs to increase. Mixer circuits used in transmitter / receiver circuits of communication devices generate signals by multiplying signals of different frequencies.

[0008] A mixer circuit (also called an active mixer) using a Gilbert cell (also called a Gilbert circuit) consists of a current-voltage (I / V) conversion section, a current switch section, and a voltage-current (V / I) conversion section (also called an amplifier section). GaN transistors, which can pass large currents, are used for the voltage-current conversion section. GaN transistors are normally-on transistors, which allow current to flow easily when they are off. Therefore, by using a normally-off Si transistor, which allows less current to flow when they are off, in the current switch section, the current that flows when they are off (leak current) can be suppressed.

[0009] However, in high-temperature environments, both GaN and Si transistors may experience increased leakage current, which may lead to increased power consumption. Furthermore, increased leakage current in switching devices may cause malfunctions.

[0010] An object of one embodiment of the present invention is to provide a semiconductor device or the like having a novel structure, a semiconductor device or the like that is excellent in low power consumption, or a semiconductor device or the like that is excellent in operational reliability.

[0011] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract other problems from the description in the specification, drawings, claims, etc. [Means for solving the problem]

[0012] One embodiment of the present invention is a semiconductor device including a current-voltage converter, a current switch unit, and a voltage-current converter, the current switch unit including a first transistor, the voltage-current converter including a second transistor, the first transistor including an oxide semiconductor in a channel formation region, the second transistor including a nitride semiconductor in a channel formation region, and the first transistor being provided above a layer in which the second transistor is provided.

[0013] One embodiment of the present invention is a semiconductor device including a current-voltage converter, a current switch unit, a voltage-current converter, and a control unit, wherein the current switch unit has a first transistor, the voltage-current converter has a second transistor, the control unit has a third transistor, the first transistor has an oxide semiconductor in a channel formation region, the second transistor has a nitride semiconductor in a channel formation region, and the third transistor has silicon in the channel formation region, and the first transistor is provided in a layer above a layer in which the second transistor and the third transistor are provided.

[0014] One embodiment of the present invention is a semiconductor device including a current-voltage converter, a current switch unit, a voltage-current converter, and a control unit, in which the current switch unit has a first transistor, the voltage-current converter has a second transistor, and the control unit has a third transistor, in which the first transistor has an oxide semiconductor in a channel formation region, the second transistor has a nitride semiconductor in a channel formation region, and the third transistor has silicon in a channel formation region, the first transistor is provided over a first substrate, the second transistor and the third transistor are provided over a second substrate, and the first substrate and the second substrate are bonded to each other, thereby electrically connecting the first transistor to the third transistor.

[0015] In one embodiment of the present invention, the current-voltage converter preferably includes a resistor element.

[0016] In one embodiment of the present invention, the voltage-current converter preferably includes a fourth transistor and an inductor, one of a source or a drain of the fourth transistor is electrically connected to a first terminal of the inductor, a second terminal of the inductor is electrically connected to a gate of the second transistor, and the fourth transistor preferably includes an oxide semiconductor in a channel formation region.

[0017] In one aspect of the present invention, the semiconductor device is preferably such that the frequency of the signal applied to the gate of the first transistor is higher than the frequency of the signal applied to the gate of the second transistor.

[0018] In one embodiment of the present invention, the oxide semiconductor preferably contains In, Ga, and Zn.

[0019] In one aspect of the present invention, the nitride semiconductor is preferably a semiconductor device containing Ga.

[0020] Other aspects of the present invention will be described in the following embodiments and in the drawings. [Effects of the Invention]

[0021] According to one embodiment of the present invention, a semiconductor device or the like having a novel structure, a semiconductor device or the like which is excellent in low power consumption, or a semiconductor device or the like which is excellent in operational reliability can be provided.

[0022] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract other effects from the description in the specification, drawings, claims, etc. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a semiconductor device. [Figure 2] 2A and 2B are diagrams illustrating an example of the configuration of a semiconductor device. [Figure 3] 3A and 3B are diagrams illustrating an example of the configuration of a semiconductor device. [Figure 4] 4A and 4B are diagrams illustrating an example of the configuration of a semiconductor device. [Figure 5] 5A and 5B are diagrams illustrating an example of the configuration of a semiconductor device. [Figure 6] 6A and 6B are diagrams illustrating a configuration example of a semiconductor device. [Figure 7] 7A and 7B are diagrams illustrating an example of the configuration of a semiconductor device. [Figure 8] 8A to 8C are diagrams illustrating an example of the configuration of a semiconductor device. [Figure 9] FIG. 9 is a diagram illustrating an example of the configuration of a wireless communication device. [Figure 10] FIG. 10 is a diagram illustrating an example of the configuration of a wireless communication device. [Figure 11] FIG. 11 is a diagram illustrating a configuration example of a semiconductor device. [Figure 12]12A to 12C are diagrams showing examples of the configuration of a transistor. [Figure 13] 13A to 13C are diagrams showing examples of the configuration of a transistor. [Figure 14] 14A to 14C are diagrams showing examples of the configuration of a transistor. [Figure 15] Figure 15A is a diagram explaining the classification of IGZO crystal structures, Figure 15B is a diagram explaining the XRD spectrum of a CAAC-IGZO film, and Figure 15C is a diagram explaining the electron microbeam diffraction pattern of a CAAC-IGZO film. [Figure 16] Figure 16A is a top view of a semiconductor wafer, and Figure 16B is an enlarged view of a chip. [Figure 17] Fig. 17A is a flowchart illustrating an example of a manufacturing process for an electronic component, and Fig. 17B is a schematic perspective view of the electronic component. [Figure 18] FIG. 18 is a diagram illustrating an example of an electronic device. [Figure 19] 19A to 19F are diagrams showing an example of an electronic device. [Figure 20] Figure 20 shows the hierarchical structure of IoT networks and trends in required specifications. [Figure 21] Figure 21 is an image diagram of factory automation. DETAILED DESCRIPTION OF THE INVENTION

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.).

[0028] 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].

[0029] (Embodiment 1) A semiconductor device according to one embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram illustrating a semiconductor device 100 according to one embodiment of the present invention, which functions as a mixer circuit (also referred to as an active mixer) using a Gilbert cell (also referred to as a Gilbert circuit). The semiconductor device 100 includes a current-voltage conversion unit 101, a current switch unit 102, and a voltage-current conversion unit 103 (also referred to as an amplifier unit).

[0030] The current-voltage converter 101 converts the flowing current I IF is converted to a voltage to produce the signal V IFThe current-voltage conversion unit 101 can be configured with a resistor element or the like. The resistor element can be configured with a semiconductor layer such as silicon. The current-voltage conversion unit 101 may also be called a current-voltage conversion circuit, or simply a circuit.

[0031] The current switch unit 102 functions as a switch that switches whether or not to cut off the current flowing between the current-voltage converter 101 and the voltage-current converter 103 in response to a signal LO. The signal LO is a signal of an arbitrary frequency that is output from an oscillation circuit or the like. The current switch unit 102 cuts off the current in response to the signal LO, thereby turning on or off the signal V RF The signal V is the signal obtained by converting the frequency of IF can be output from the current-voltage conversion unit 101. The current switch unit 102 may be called a current switch circuit or simply a circuit.

[0032] The current switch unit 102 includes a transistor 111 that functions as a switch that can block current. The transistor 111 is preferably an OS transistor in which a semiconductor layer 112 having a channel formation region is made of an oxide semiconductor (also referred to as metal oxide). Note that the operation and the like of the OS transistor will be described as an n-channel transistor.

[0033] Because the band gap of an oxide semiconductor is 2.5 eV or more, an OS transistor has an extremely small off-state current. For example, the off-state current per 1 μm of channel width can be reduced to 1×10 at room temperature (25°C) with a source-drain voltage of 3.5 V. -20 Less than A, 1 x 10 -22 Less than A or 1 x 10 -24 In other words, the current switch section 102 can make the leakage current that flows when it is turned off extremely small.

[0034] High-density integrated semiconductor devices may generate heat due to circuit operation. This heat increases the temperature of transistors, which can change the characteristics of the transistors, resulting in changes in field-effect mobility and a decrease in operating frequency. OS transistors have higher heat resistance than Si transistors, making them less susceptible to temperature-induced changes in field-effect mobility and a decrease in operating frequency. Furthermore, OS transistors tend to maintain the characteristic that their drain current increases exponentially with respect to the gate-source voltage, even at high temperatures. Therefore, OS transistors enable stable operation in high-temperature environments.

[0035] Examples of oxide semiconductors that can be used in OS transistors include Zn oxide, Zn-Sn oxide, Ga-Sn oxide, In-Ga oxide, In-Zn oxide, and In-M-Zn oxide (where M is Ti, Ga, Y, Zr, La, Ce, Nd, Sn, or Hf). In particular, an oxide semiconductor using Ga as M is preferably used in an OS transistor because it can provide a transistor with excellent electrical characteristics, such as field-effect mobility, by adjusting the ratio of elements. The oxide containing indium and zinc may also contain one or more elements selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the like.

[0036] To improve the reliability and electrical characteristics of an OS transistor, the oxide semiconductor used in the semiconductor layer is preferably an oxide semiconductor having a crystalline part, such as CAAC-OS, CAC-OS, or nc-OS. CAAC-OS is an abbreviation for c-axis-aligned crystalline oxide semiconductor. CAC-OS is an abbreviation for cloud-aligned composite oxide semiconductor. nc-OS is an abbreviation for nanocrystalline oxide semiconductor.

[0037] 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.

[0038] CAC-OS has the function of both allowing electrons (or holes) to flow and preventing electrons from flowing. By separating the electron flow function from the electron blocking function, both functions can be maximized. In other words, using CAC-OS in the channel formation region of an OS transistor can achieve both a high on-state current and an extremely low off-state current.

[0039] Oxide semiconductors have a wide band gap, which makes it difficult for electrons to be excited, and have a large effective mass for holes. Therefore, compared with general Si transistors, OS transistors may be less susceptible to avalanche breakdown and other problems. Therefore, for example, hot carrier degradation caused by avalanche breakdown can be suppressed. Suppressing hot carrier degradation allows OS transistors to be driven at a high drain voltage.

[0040] OS transistors are accumulation-type transistors that use electrons as majority carriers. Therefore, they are less susceptible to drain-induced barrier lowering (DIBL), a short-channel effect, compared to inversion-type transistors (typically, Si transistors) with pn junctions. In other words, OS transistors have higher resistance to short-channel effects than Si transistors.

[0041] Because OS transistors have high resistance to short-channel effects, their channel length can be reduced without degrading their reliability, allowing for increased circuit integration. As the channel length decreases, the drain electric field becomes stronger, but as mentioned above, OS transistors are less susceptible to avalanche breakdown than Si transistors.

[0042] Furthermore, because OS transistors have high resistance to short-channel effects, their gate insulating films can be thicker than those of Si transistors. For example, even for miniaturized transistors with channel lengths and widths of 50 nm or less, it may be possible to provide a gate insulating film as thick as about 10 nm. By increasing the gate insulating film thickness, parasitic capacitance can be reduced, thereby improving the operating speed of the circuit. Furthermore, by increasing the gate insulating film thickness, leakage current through the gate insulating film can be reduced, leading to a reduction in static current consumption.

[0043] As described above, the current switch unit 102 can reduce the current (leakage current) that flows when the current switch unit 102 is off by including an OS transistor. In addition, a layer including an OS transistor can be provided on top of a layer including another transistor. That is, the current switch unit 102 can be provided stacked on a layer including transistors that constitute the current-voltage converter unit 101 and the voltage-current converter unit 103. This allows the current switch unit 102 to be arranged without increasing the circuit area. In other words, the circuit area in which transistors can be arranged increases, allowing the amount of current that the transistors in the current switch unit 102 pass to be increased.

[0044] The voltage-to-current converter 103 converts the signal V RF is converted to a current, and the current I RF It has the function of controlling the current I RF is a current whose cutoff is controlled by the current switch unit 102. RF is an externally applied signal. RF The frequency of the signal V is higher than the frequency of the signal LO. RF Current I according toRF The voltage-current converter 103 may be referred to as a voltage-current converter circuit or simply as a circuit.

[0045] The voltage-to-current converter 103 converts the signal V RF The current I RF The transistor 121 has a transistor 121 through which a current flows. The transistor 121 is preferably a transistor (GaN transistor) in which a semiconductor layer 122 having a channel formation region has a nitride semiconductor (nitride semiconductor) containing a group 13 element (such as gallium) in the channel formation region. A typical example is a transistor having gallium nitride (hereinafter, GaN) in the channel formation region. Note that, although a transistor having GaN in the channel formation region will be described as an example of a GaN transistor, AlGaN or AlN may also be used. Alternatively, a high-mobility transistor other than a nitride semiconductor may be used, and a transistor having SiC or the like in the channel formation region may also be used.

[0046] When the semiconductor layer 122 is made of GaN, it is preferable to stack it with AlGaN. Aluminum nitride (AlN) has excellent material properties, including a band gap (6.2 eV) approximately twice that of GaN (3.4 V), an electrostatic breakdown field (12 MV / cm) approximately four times that of GaN (3.3 MV / cm), and a thermal conductivity (2.9 W / cmK) approximately 1.5 times that of GaN (2 W / cmK). AlGaN, an alloy of AlN and GaN, is a desirable material for high-power, high-frequency devices. High-electron mobility transistors (HEMTs) with AlGaN as the channel region can operate at higher voltages than HEMTs with GaN as the channel region. Furthermore, two-dimensional electron gas (2DEG) can be generated at the interface between GaN and AlGaN due to the polarization effect between GaN and AlGaN, enabling use as a high-mobility transistor.

[0047] 2A is a diagram illustrating a specific configuration example of a semiconductor device 100 according to one embodiment of the present invention. The semiconductor device 100 includes a current-voltage converter 101, a current switch 102, and a voltage-current converter 103, as described with reference to FIG.

[0048] The current-voltage conversion unit 101 includes a resistance element 131A and a resistance element 131B. The current switch unit 102 receives a signal LO + Transistor 111A is supplied with signal LO - The signal LO is applied to the transistor 111B. - is the signal LO + Signal LO is the inverted signal of + The voltage-current converter 103 may be referred to as a signal LO. The transistors 111A and 111B are OS transistors. RF The transistor 121A is a GaN transistor.

[0049] The semiconductor device 100 receives a signal V RF , signal LO, and signal V according to the frequency of IF Outputs the signal V IF The frequency of the signal V RF If the frequency of signal LO is f1 and the frequency of signal LO is f2, a signal with a frequency of (f1-f2) or (f1+f2) can be generated. Note that because GaN transistors have higher field-effect mobility than OS transistors, it is preferable to set frequency f1 higher than frequency f2. This configuration makes it possible to widen the frequency band that can be input.

[0050] The transistors 111A and 111B and the transistor 121A shown in Fig. 2A can be stacked in different layers over a substrate. Fig. 2B is a diagram schematically illustrating layers including transistors stacked over a substrate in the semiconductor device 100 of one embodiment of the present invention.

[0051] 2B shows a schematic diagram of the semiconductor device 100, which includes a substrate 140, a layer 141 including the transistor 121 (transistor 121A), and a layer 142 including the transistor 111 (transistors 111A and 111B). The layer 142 including the transistor 111 is provided above the layer 141 including the transistor 121. That is, the transistor 111 can be provided above the layer including the transistor 121. Since the circuit area in which the OS transistor can be disposed increases, the amount of current flowing through the transistors of the current switch unit 102 can be increased.

[0052] Note that a substrate containing silicon, such as a SIMOX (Separation by Implanted Oxygen) substrate or an SOI substrate, can be used as the substrate 140. This is preferable because a transistor having silicon in a channel formation region (Si transistor) can be provided in or on the substrate.

[0053] The signal LO and the signal V are supplied to the current switch unit 102 and the voltage-to-current converter 103, respectively, as shown in FIG. RF is output from the control unit. This configuration will be described with reference to Figures 3A and 3B.

[0054] The semiconductor device 100A shown in Fig. 3A corresponds to a configuration including a control unit 104A and a control unit 104B in addition to the configuration shown in Fig. 1. The control unit 104A and the control unit 104B have a function as a signal output unit such as an oscillation circuit.

[0055] The control units 104A and 104B each have a transistor 131 that functions as a bias generation circuit or an oscillation circuit capable of generating a bias voltage. The transistor 131 is preferably a transistor that can constitute a bias generation circuit or an oscillation circuit. For example, a transistor in which the semiconductor layer 132 having a channel formation region is made of silicon (Si transistor) is suitable. Si transistors can be configured as a complementary circuit using n-channel transistors and p-channel transistors, and are therefore suitable for circuits that function as logic circuits or oscillation circuits. The control units 104A and 104B may also be referred to as control circuits or simply as circuits.

[0056] Note that the transistor 131, which is a Si transistor, can be stacked in different layers over a substrate. Figure 3B is a diagram schematically illustrating layers including a transistor stacked over a substrate in the semiconductor device 100A of one embodiment of the present invention.

[0057] 3B shows a schematic diagram of semiconductor device 100A, which includes substrate 140, layer 141, and layer 142 shown in FIG. 2B, as well as layer 143 having transistor 131. Layer 142 is provided above layer 141 and layer 143. That is, transistor 111 can be provided above the layer in which transistor 121 and transistor 131 are provided. Since the circuit area in which OS transistors can be disposed increases, the amount of current passed by the transistors of current switch unit 102 can be increased.

[0058] Fig. 4A is a diagram illustrating a specific configuration example of a modified example of the semiconductor device 100 described above in Fig. 2A. The semiconductor device 100B illustrated in Fig. 4A includes a current-voltage conversion unit 101, a current switch unit 102, and a voltage-current conversion unit 103, as described in Fig. 1.

[0059] The transistor 111A and the transistor 111B of the current switch unit 102 shown in FIG. 4A have back gate electrodes. The back gate electrodes are supplied with a back gate voltage VBG The OS transistors 111A and 111B are supplied with a back gate voltage V BG The electrical characteristics, such as the threshold voltage, can be controlled by the gate electrode. Therefore, the electrical characteristics of the transistor can be switched between normally-off and normally-on. Note that the back gate electrode of the OS transistor may be connected to the gate electrode. This configuration can increase the amount of current that flows in the on state.

[0060] Fig. 4B is a diagram for explaining a specific configuration example of another modified example of the semiconductor device 100 described in Fig. 2A above. The semiconductor device 100C shown in Fig. 4B has a current-voltage conversion unit 101, a current switch unit 102, and a voltage-current conversion unit 103, as described in Fig. 1. The mixer circuit shown in Fig. 4B corresponds to a double-balanced mixer circuit, which is different from the single-balanced mixer circuit described in Fig. 2A.

[0061] The current-voltage converter 101 includes a resistor element 131A and a resistor element 131B. The current-voltage converter 101 converts a signal V IF + and V IF - Outputs the signal V IF - is the signal V IF + The signal V is the inverted signal of IF + is the signal V IF The current switch unit 102 outputs the signal LO + Transistor 111A and transistor 111D are supplied with signal LO - The voltage-current converter 103 includes a transistor 111B and a transistor 111C to which a signal V is applied. The transistors 111A to 111D are OS transistors. RF + a transistor 121A to which a signal V RF -The transistors 121A and 121B are GaN transistors. RF - is the signal V RF + The signal V is the inverted signal of RF + is the signal V RF This is sometimes the case.

[0062] The semiconductor device 100C receives the signal V RF , signal LO, and signal V according to the frequency of IF Outputs the signal V IF The frequency of the signal V RF If the frequency of the signal is f1 and the frequency of the signal LO is f2, then the signal V with a frequency of (f1-f2) or (f1+f2) IF + and V IF - can be generated.

[0063] Fig. 5A is a diagram illustrating a specific configuration example of another modified example of the semiconductor device 100 described in Fig. 2A above. The semiconductor device 100D illustrated in Fig. 5A includes a bias voltage holding unit 105 in addition to the current-voltage conversion unit 101, the current switch unit 102, and the voltage-current conversion unit 103 described in Fig. 1.

[0064] The bias voltage holding unit 105 has a function of holding a bias voltage for operating the voltage-current conversion unit 103. By holding the bias voltage in the bias voltage holding unit 105, the voltage-current conversion unit 103 can operate in response to the input signal V RF Current I according to RF The bias voltage holding unit 105 may be referred to as a bias voltage holding circuit, or simply as a circuit or a holding circuit.

[0065] The bias voltage holding unit 105 includes a capacitive element 151, an inductor 152, a transistor 153, and a capacitive element 154. The transistor 153 is connected to a control signal S WBy controlling the inductor 152, the node N g bias voltage V bias By using an OS transistor as the transistor 153, the off-state current can be made extremely small. Therefore, by turning off the transistor 153, the bias voltage holding unit 105 g The bias voltage V applied to bias can continue to hold.

[0066] 5B shows a timing chart for explaining the operation of the bias voltage holding unit 105 in FIG. 5A. As shown in FIG. 5B, the control signal S W is set to H level, turning on the transistor 153 which functions as a switch. g is the bias voltage V bias By turning off the transistor 153, the bias voltage V bias is node N g A signal V RF Given a signal V RF Following the change of g The bias voltage V bias This change in potential causes the current I flowing through the transistor 121A to RF can be made larger.

[0067] The inductor 152 shown in Fig. 5A can be provided by stacking different layers on a substrate by processing a conductor into a predetermined shape. Fig. 6A and Fig. 6B are diagrams schematically illustrating a layer including a transistor and a layer including an inductor stacked over a substrate in the semiconductor device 100 of one embodiment of the present invention.

[0068] The schematic diagram of the semiconductor device 100E shown in FIG. 6A shows the substrate 140, layers 141, 142, and 143 shown in FIG. 3B, as well as a layer 144 including an inductor 152. The layer 144 is provided above the layer 142. That is, the layer 144 including the inductor 152 can be provided above a layer including a transistor. Alternatively, as in the semiconductor device 100F shown in FIG. 6B, the layer 144 can be provided between layers including transistors. Note that the inductor may be formed, for example, with a conductor having a thickness of approximately 2 μm. By configuring the semiconductor devices 100E and 100F, a structure including the bias voltage holding unit 105 can be formed on the substrate.

[0069] 7A is a diagram illustrating a specific configuration example of another modified example of the semiconductor device 100 described in FIG. 2A. In FIG. 7A, the transistor sizes of the transistors 111A and 111B of the current switch unit 102 in the semiconductor device 100G are schematically illustrated to be larger than the transistor 121A of the voltage-current converter 103.

[0070] By making the transistor sizes of transistors 111A and 111B of the current switch unit 102 larger than the transistor size of transistor 121A of the voltage-current converter 103, switching can be performed without limiting the amount of current determined by the transistors of the voltage-current converter 103. OS transistors have a smaller amount of current than GaN transistors of the same transistor size. Therefore, it is preferable that the channel length of the OS transistor be shorter than the channel length of the GaN transistor. It is also preferable that the channel width of the OS transistor be larger than the channel width of the GaN transistor. With this configuration, the amount of current flowing through the current switch unit 102 can be made closer to that of the voltage-current converter 103.

[0071] Note that when increasing the sizes of the OS transistors, transistors 111A and 111B, in the current switch unit 102, the circuit area in which the OS transistors can be arranged is preferably large. For example, as shown in the schematic diagram of a semiconductor device 100H in FIG. 7B , the circuit area in which the OS transistors can be arranged can be increased by stacking the layer 142, which is a layer including OS transistors, as multiple layers 142A and 142B.

[0072] 8A to 8C are diagrams for explaining specific configuration examples of the stacked configuration of the semiconductor device 100A etc. described in Fig. 3B etc. The block diagrams shown in Fig. 8A to 8C schematically show the arrangement of each component (layer 141, layer 142, layer 143) on the substrate 140 described in Fig. 3B etc.

[0073] 8A illustrates layers 141, 142, and 143 provided on substrate 140, as well as transistor 131, which is a GaN transistor, and a buffer layer 145 provided between layer 141 and substrate 140. Buffer layer 145 is provided to form a different type of semiconductor layer, a nitride semiconductor such as GaN, on substrate 140. The configuration of FIG. 8A makes it possible to provide layer 141 having transistor 121 and layer 143 having transistor 131 on substrate 140, and then stack layer 142 having transistor 111 thereon.

[0074] 8B illustrates a configuration example in which a semiconductor device is fabricated by bonding a substrate 140, in which a layer 141 is provided on a buffer layer 145, to a substrate 146, in which a layer 143 including a transistor 131 and a layer 142 including a transistor 111 are stacked. Because the transistor 121 included in the layer 141 is a Si transistor, a silicon-containing substrate such as a SIMOX substrate or an SOI substrate can be used for the substrate 146. Techniques for bonding the substrates include plasma activated bonding and substrate bonding techniques such as Cu-Cu bonding.

[0075] 8C illustrates a configuration example in which a semiconductor device is fabricated by electrically connecting the transistors by bonding a substrate 140 on which the layer 143 and the layer 141 over the buffer layer 145 are provided to a substrate 147 on which a layer 142 including the transistor 111 is stacked. Because the transistor 121 included in the layer 142 is an OS transistor, the substrate 147 can be a silicon substrate or a glass substrate.

[0076] One embodiment of the present invention provides a semiconductor device that functions as an active mixer and includes a current-voltage converter, a current switch, and a voltage-current converter. The transistors in the current switch and voltage-current converter are OS transistors and GaN transistors, respectively. Therefore, a semiconductor device or the like that can reduce a change in off-state current due to a change in transistor characteristics and achieves excellent low power consumption can be provided. Alternatively, a semiconductor device or the like that has excellent operational reliability can be provided even in a high-temperature environment where transistor characteristics are likely to change. Furthermore, a layer including an OS transistor can be stacked with transistors having different types of semiconductor layers, such as a GaN transistor and a Si transistor, thereby enabling a miniaturized semiconductor device or the like to be provided.

[0077] (Embodiment 2) In this embodiment, a configuration example of a wireless communication device having an integrated circuit including the semiconductor device 100 described in the above embodiment will be described with reference to Figs. 9 and 10. In this embodiment, a smartphone will be described as an example of the wireless communication device, but other wireless communication terminals such as a portable game console, a tablet PC (Personal Computer), and a notebook PC may also be used. In addition, the wireless communication device according to this embodiment can be applied to devices capable of wireless communication.

[0078] 9 includes an antenna ANT, an application processor 11, a baseband processor 12, an integrated circuit (IC) 13, a memory 14, a battery 15, a power management IC (PMIC) 16, a display unit 17, a camera unit 18, an operation input unit 19, an audio IC 20, a microphone 21, and a speaker 22. The integrated circuit 13 is also called an RF (Radio Frequency) IC or a wireless chip.

[0079] In order to support 5G communication standards, multiple antennas ANT are provided to correspond to multiple frequency bands.

[0080] The application processor 11 has a function of reading out programs stored in the memory 14 and performing processing to realize various functions of the wireless communication device 10. For example, the application processor 11 has a function of executing an OS (Operating System) program from the memory 14 and also executing application programs that operate on the OS program.

[0081] The baseband processor 12 has a function of performing baseband processing including encoding (e.g., error correction coding) processing or decoding processing on data transmitted and received by the wireless communication device 10. Specifically, the baseband processor 12 has a function of receiving transmission data from the application processor 11, encoding the received transmission data, and transmitting the encoded data to the integrated circuit 13. The baseband processor 12 also has a function of receiving reception data from the integrated circuit 13, decoding the received reception data, and transmitting the encoded data to the application processor 11.

[0082] The integrated circuit 13 has a function of performing modulation or demodulation processing on data transmitted and received by the wireless communication device 10. Specifically, the integrated circuit 13 has a function of modulating transmission data received from the baseband processor 12 with a carrier wave to generate a transmission signal, and outputting the transmission signal via the antenna ANT. The integrated circuit 13 also has a function of receiving a reception signal via the antenna ANT, demodulating the reception signal with a carrier wave to generate reception data, and transmitting the reception data to the baseband processor 12.

[0083] The memory 14 has a function of storing programs and data used by the application processor 11. The memory 14 includes a non-volatile memory that retains stored data even when the power is cut off, and a volatile memory that clears stored data when the power is cut off.

[0084] The battery 15 is used when the wireless communication device 10 operates without relying on an external power supply. The wireless communication device 10 can use the power of the battery 15 even when an external power supply is connected. It is preferable to use a secondary battery that can be charged and discharged as the battery 15.

[0085] The power management IC 16 has a function of generating an internal power supply voltage from the battery 15 or an external power supply. This internal power supply voltage is provided to each block of the wireless communication device 10. At this time, the power management IC 16 has a function of controlling the internal power supply voltage for each block that receives the internal power supply voltage. The power management IC 16 controls the internal power supply voltage based on instructions from the application processor 11. Furthermore, the power management IC 16 can also control the supply and cut-off of the internal power supply voltage for each block. The power management IC 16 also has a function of controlling charging of the battery 15 when power is supplied from an external power supply device.

[0086] Display unit 17 is a liquid crystal display device or a light-emitting display device, and has the function of displaying various images in accordance with the processing in application processor 11. The images displayed on display unit 17 include user interface images that allow the user to give operational instructions to wireless communication device 10, camera images, videos, and the like.

[0087] The camera unit 18 has a function of acquiring images in accordance with instructions from the application processor 11. The operation input unit 19 has a function as a user interface that is operated by the user to give operation instructions to the wireless communication device 10. The audio IC 20 has a function of decoding audio data transmitted from the application processor 11 and driving the speaker 22. In addition, the audio IC 20 has a function of encoding audio information obtained from the microphone 21 to generate audio data and outputting the audio data to the application processor 11.

[0088] Fig. 10 is a block diagram illustrating an example configuration of integrated circuit 13. Integrated circuit 13 shown in Fig. 10 includes low-noise amplifier 201, mixer 202, low-pass filter 203, variable gain amplifier 204, analog-to-digital conversion circuit 205, interface unit 206, digital-to-analog conversion circuit 207, variable gain amplifier 208, low-pass filter 209, mixer 210, power amplifier 211, and oscillation circuit 212. Also illustrated in Fig. 10 are antenna ANT, duplexer DUP, and baseband processor 12. Note that low-noise amplifier 201, mixer 202, low-pass filter 203, variable gain amplifier 204, and analog-to-digital conversion circuit 205 may be referred to as a receiving circuit block, and digital-to-analog conversion circuit 207, variable gain amplifier 208, low-pass filter 209, mixer 210, and power amplifier 211 may be referred to as a transmitting circuit block.

[0089] The baseband processor 12 and the integrated circuit 13 are realized by individual semiconductor chips. The duplexer DUP includes an antenna switch and the like.

[0090] The low-noise amplifier 201 amplifies the signal received by the antenna ANT with low noise. The mixer 202 corresponds to a configuration including the semiconductor device 100 described in the first embodiment above. The mixer 202 demodulates and down-converts (frequency converts) the signal using a signal from the oscillation circuit 212. The low-pass filter 203 removes unnecessary high-frequency components from the signal from the mixer 202. The variable gain amplifier 204 amplifies the output signal of the low-pass filter 203 with a gain that takes into account the input range of the analog-to-digital conversion circuit 205. The analog-to-digital conversion circuit 205 converts the analog signal from the variable gain amplifier 204 into a digital signal. The digital signal is output to the baseband processor 12 via the interface unit 206.

[0091] Digital-to-analog conversion circuit 207 converts the digital signal received by interface unit 206 into an analog signal. Variable gain amplifier 208 amplifies the output signal of digital-to-analog conversion circuit 207. Low-pass filter 209 removes unnecessary high-frequency components from the signal from variable gain amplifier 208. Mixer 210 corresponds to the configuration including semiconductor device 100 described in the first embodiment above. Mixer 210 performs modulation and up-conversion (frequency conversion) using a signal from oscillation circuit 212. Power amplifier 211 amplifies the output signal of mixer 210 with a predetermined gain and outputs it.

[0092] The structures, configurations, methods, and the like described in this embodiment can be used in appropriate combination with structures, configurations, methods, and the like described in other embodiments.

[0093] (Embodiment 3) In this embodiment, a structure of a transistor applicable to the semiconductor device described in the above embodiment will be described. As an example, a structure in which transistors having different electrical characteristics are stacked will be described. By using this structure, the degree of freedom in designing a semiconductor device can be increased. In addition, by stacking transistors having different electrical characteristics, the degree of integration of a semiconductor device can be increased.

[0094] FIG. 11 shows a part of a cross-sectional structure of a semiconductor device. The semiconductor device shown in FIG. 11 includes a transistor 550, a transistor 500, a transistor 650, and a capacitor 600. FIG. 12A is a cross-sectional view of the transistor 500 in the channel length direction, FIG. 12B is a cross-sectional view of the transistor 500 in the channel width direction, and FIG. 12C is a cross-sectional view of the transistor 550 in the channel width direction. For example, the transistor 500 corresponds to the transistor 111, the transistor 550 corresponds to the transistor 131, and the transistor 650 corresponds to the transistor 121, all of which are shown in the above embodiments. The capacitor 600 corresponds to the capacitor 151.

[0095] 11, the transistor 500 is provided above the transistors 550 and 650, and the capacitor 600 is provided above the transistors 550, 650, and 500. In FIG.

[0096] The transistor 550 is provided over a substrate 311 and includes a conductor 316, an insulator 315, a semiconductor region 313 made of part of the substrate 311, a low-resistance region 314a functioning as a source region or a drain region, and a low-resistance region 314b.

[0097] 12C , in the transistor 550, the top surface and the side surfaces in the channel width direction of the semiconductor region 313 are covered with a conductor 316 via an insulator 315. By forming the transistor 550 as a fin type in this manner, the effective channel width is increased, thereby improving the on-state characteristics of the transistor 550. Furthermore, the contribution of the electric field of the gate electrode can be increased, thereby improving the off-state characteristics of the transistor 550.

[0098] Note that the transistor 550 may be either a p-channel transistor or an n-channel transistor.

[0099] The region where the channel of the semiconductor region 313 is formed, the region nearby, the low-resistance region 314a that serves as the source region or drain region, and the low-resistance region 314b preferably contain a semiconductor such as a silicon-based semiconductor, and preferably contain single-crystal silicon. Alternatively, they may be formed of a material containing Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), or the like. A configuration using silicon in which the effective mass is controlled by applying stress to the crystal lattice and changing the lattice spacing may also be used. Alternatively, the transistor 550 may be a HEMT (High Electron Mobility Transistor) by using GaAs and GaAlAs, or the like.

[0100] The low resistance region 314a and the low resistance region 314b contain, in addition to the semiconductor material applied to the semiconductor region 313, an element that imparts n-type conductivity, such as arsenic or phosphorus, or an element that imparts p-type conductivity, such as boron.

[0101] The conductor 316 functioning as the gate electrode can be made of a conductive material such as a semiconductor material, metal material, alloy material, or metal oxide material, such as silicon containing an element that imparts n-type conductivity, such as arsenic or phosphorus, or an element that imparts p-type conductivity, such as boron.

[0102] Since the work function is determined by the material of the conductor, the threshold voltage of the transistor can be adjusted by selecting the material of the conductor. Specifically, it is preferable to use a material such as titanium nitride or tantalum nitride as the conductor. Furthermore, in order to achieve both conductivity and embeddability, it is preferable to use a metal material such as tungsten or aluminum as the conductor in a laminated state, and tungsten is particularly preferable in terms of heat resistance.

[0103] The transistor 550 may be formed using an SOI (Silicon on Insulator) substrate or the like.

[0104] The SOI substrate may be a SIMOX (Separation by Implanted Oxygen) substrate formed by implanting oxygen ions into a mirror-polished wafer and then heating it at a high temperature to form an oxide layer to a certain depth from the surface and eliminate defects that have occurred in the surface layer, or an SOI substrate formed using the Smart Cut method or the ELTRAN (registered trademark: Epitaxial Layer Transfer) method, which cleaves a semiconductor substrate by utilizing the growth of microvoids formed by hydrogen ion implantation through heat treatment. A transistor formed using a single crystal substrate has a single crystal semiconductor in the channel formation region.

[0105] Here, the transistor 650 will be described. The transistor 650 is formed over the same substrate as the transistor 550. The transistor 650 is formed using a semiconductor layer formed over a single crystal silicon substrate, a sapphire substrate, or an SOI substrate. The transistor 650 is a nitride semiconductor having gallium in a channel formation region. The semiconductor layer preferably has a crystal structure containing gallium. An example of a semiconductor layer containing gallium is gallium nitride (hereinafter, referred to as GaN).

[0106] A semiconductor device using GaN for the semiconductor layer 654 will be described with reference to Fig. 11. For example, GaN can be formed by providing a buffer layer 652 on the substrate 311 and epitaxially growing single-crystal GaN on the buffer layer 652. The single-crystal GaN formed by epitaxial growth corresponds to the semiconductor layer 654. Note that Fig. 11 shows an example in which a single-crystal silicon substrate is used for the substrate 311.

[0107] When forming the transistor 650, it is preferable to use a semiconductor layer in which a semiconductor layer 656 is epitaxially grown on a semiconductor layer 654. When the semiconductor layer 654 is GaN, the semiconductor layer 656 is preferably AlGaN. For example, aluminum nitride (AlN) is known to have excellent material properties, such as a band gap (6.2 eV) approximately twice that of GaN, an electrostatic breakdown field (12 MV / cm) approximately four times that of GaN, and a thermal conductivity (2.9 W / cmK) approximately 1.5 times that of GaN. Therefore, AlN and AlGaN, an alloy of AlN and GaN, are preferable materials for high-power, high-frequency devices. A high-electron mobility transistor (HEMT) with an AlGaN channel region can operate at a higher voltage than a HEMT with a GaN channel region. At the interface between GaN and AlGaN, a two-dimensional electron gas (2DEG) is generated due to the polarization effect between GaN and AlGaN. In other words, in a transistor with a HEMT structure, the 2DEG serves as the channel region.

[0108] The conductor 330 is provided over the semiconductor layer 656. The conductor 330 corresponds to the source or drain of the transistor 650.

[0109] The insulator 324 is sandwiched between the conductor 658 and the semiconductor layer 656. The conductor 658 can also be a gate electrode, and the insulator 324 can also be a gate insulator of the transistor 650. The insulator 324 can be made of silicon oxide, aluminum oxide, hafnium oxide, or the like. For example, the insulator 324 containing any one of silicon oxide, aluminum oxide, and hafnium oxide reduces the off-state current of the transistor 650. To describe the gate insulator in more detail, the gate insulator is preferably a SiO2 film, an Al2O3 film, or a HfO2 film.

[0110] The transistor 650 preferably has a recessed gate structure. FIG. 11 illustrates an example in which the transistor 650 has a recessed gate structure. The recessed gate structure of the transistor 650 reduces the off-state current of the transistor 650. The recessed gate structure is formed by thinning the semiconductor layer 656 by etching a portion of the semiconductor layer 656 that overlaps with a gate electrode forming a channel formation region. The region of the semiconductor layer 656 that is thinned by etching is called a recessed region. The recessed region can have a high threshold voltage due to enhanced depletion of the 2DEG. The non-recessed region can pass a large current due to an increased concentration of the 2DEG.

[0111] An insulator 320, an insulator 322, an insulator 324, and an insulator 326 are stacked in this order over the transistor 550.

[0112] The insulators 320, 322, 324, and 326 can be made of, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, aluminum nitride, or the like.

[0113] 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.

[0114] The insulator 322 may function as a planarizing film that flattens steps caused by the transistor 550 or the like provided thereunder. For example, the top surface of the insulator 322 may be planarized by planarization treatment using a chemical mechanical polishing (CMP) method or the like to improve the planarity.

[0115] The insulator 324 is preferably a film having a barrier property that prevents hydrogen or impurities from diffusing from the substrate 311, the transistor 550, or the like to a region where the transistor 500 is provided.

[0116] As an example of a film having a barrier property against hydrogen, for example, silicon nitride formed by a CVD method can be suitably used. Here, diffusion of hydrogen into a semiconductor element having an oxide semiconductor, such as the transistor 500, may degrade the characteristics of the semiconductor element. Therefore, it is preferable to use a film that suppresses hydrogen diffusion between the transistor 500 and the transistor 550. Specifically, the film that suppresses hydrogen diffusion is a film that releases a small amount of hydrogen.

[0117] The amount of desorption of hydrogen can be analyzed using, for example, thermal desorption spectroscopy (TDS). For example, the amount of desorption of hydrogen from the insulator 324 is calculated as 10×10 per area of ​​the insulator 324 when the surface temperature of the film is in the range of 50° C. to 500° C. in TDS analysis. 15 atoms / cm 2 Less than or equal to 5 x 10 15 atoms / cm 2 The following is fine.

[0118] 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.

[0119] Conductors 328 and 330, which connect to the capacitor 600 or the transistor 500, are embedded in the insulators 320, 322, 324, and 326. The conductor 330 functions as a source or drain electrode of the transistor 650. The conductors 328 and 330 also function as plugs or wiring. A plurality of conductors that function as plugs or wiring may be collectively assigned the same reference numeral. In this specification and the like, a wiring and a plug connected to the wiring may be integrated. That is, a part of a conductor may function as a wiring, and a part of a conductor may function as a plug.

[0120] 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 laminated layer. High-melting-point materials such as tungsten and molybdenum, which have both heat resistance and conductivity, are preferably used, and tungsten is preferred. Alternatively, they are preferably formed from a low-resistance conductive material such as aluminum or copper. The use of a low-resistance conductive material can reduce the wiring resistance.

[0121] A wiring layer may be provided over the insulator 326 and the conductor 330. For example, in FIG. 11, the insulator 350, the insulator 352, and the insulator 354 are stacked in this order. The conductor 356 is formed in the insulator 350, the insulator 352, and the insulator 354. The conductor 356 functions as a plug connected to the transistor 550, a plug connected to the transistor 650, or a wiring. Note that the conductor 356 can be formed using a material similar to that of the conductor 328 and the conductor 330.

[0122] 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 of the insulator 350 having a barrier property against hydrogen. With this structure, the transistor 550 or the transistor 650 can be separated from the transistor 500 by a barrier layer, and diffusion of hydrogen from the transistor 550 or the transistor 650 to the transistor 500 can be suppressed.

[0123] Note that, for example, tantalum nitride or the like is preferably used as a conductor having a barrier property against hydrogen. Stacking tantalum nitride and highly conductive tungsten can suppress diffusion of hydrogen from the transistor 550 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.

[0124] A wiring layer may be provided over the insulator 354 and the conductor 356. For example, in FIG. 11, an insulator 360, an insulator 362, and an insulator 364 are stacked in this order. A conductor 366 is formed in the insulator 360, the insulator 362, and the insulator 364. The conductor 366 functions as a plug or a wiring. The conductor 366 can be formed using the same material as the conductors 328 and 330.

[0125] Note that, for example, the insulator 360 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 366 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 of the insulator 360 having a barrier property against hydrogen. With this structure, the transistor 550 or the transistor 650 can be separated from the transistor 500 by a barrier layer, and diffusion of hydrogen from the transistor 550 or the transistor 650 to the transistor 500 can be suppressed.

[0126] A wiring layer may be provided over the insulator 364 and the conductor 366. For example, in FIG. 11, an insulator 370, an insulator 372, and an insulator 374 are stacked in this order. A conductor 376 is formed in the insulator 370, the insulator 372, and the insulator 374. The conductor 376 functions as a plug or wiring. The conductor 376 can be formed using a material similar to that of the conductors 328 and 330.

[0127] Note that, for example, the insulator 370 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 376 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 of the insulator 370 having a barrier property against hydrogen. With this structure, the transistor 550 or the transistor 650 can be separated from the transistor 500 by a barrier layer, and diffusion of hydrogen from the transistor 550 or the transistor 650 to the transistor 500 can be suppressed.

[0128] A wiring layer may be provided over the insulator 374 and the conductor 376. For example, in FIG. 11, an insulator 380, an insulator 382, ​​and an insulator 384 are stacked in this order. A conductor 386 is formed in the insulator 380, the insulator 382, ​​and the insulator 384. The conductor 386 functions as a plug or wiring. The conductor 386 can be formed using a material similar to that of the conductor 328 and the conductor 330.

[0129] Note that, for example, the insulator 380 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 386 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 of the insulator 380 having a barrier property against hydrogen. With this structure, the transistor 550 or the transistor 650 can be separated from the transistor 500 by a barrier layer, and diffusion of hydrogen from the transistor 550 or the transistor 650 to the transistor 500 can be suppressed.

[0130] Although the above describes a wiring layer including the conductor 356, a wiring layer including the conductor 366, a wiring layer including the conductor 376, and a wiring layer including the conductor 386, the semiconductor device according to this embodiment is not limited to this. There may be three or fewer wiring layers similar to the wiring layer including the conductor 356, or there may be five or more wiring layers similar to the wiring layer including the conductor 356.

[0131] An insulator 510, an insulator 512, an insulator 514, and an insulator 516 are stacked in this order on the insulator 384. Any of the insulator 510, the insulator 512, the insulator 514, and the insulator 516 is preferably made of a substance that has a barrier property against oxygen and hydrogen.

[0132] For example, the insulator 510 and the insulator 514 are preferably formed using a film having a barrier property that prevents hydrogen or impurities from diffusing from the substrate 311, the region where the transistor 550 is provided, or the region where the transistor 650 is provided to the region where the transistor 500 is provided. Therefore, the insulator 510 and the insulator 514 can be formed using a material similar to that of the insulator 324.

[0133] An example of a film having a barrier property 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 500, may degrade the characteristics of the semiconductor element. Therefore, it is preferable to use a film that suppresses hydrogen diffusion between the transistor 500 and the transistor 550 or the transistor 650. Specifically, the film that suppresses hydrogen diffusion is a film that releases a small amount of hydrogen.

[0134] 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.

[0135] In particular, aluminum oxide has a high blocking effect against 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 500 during and after the transistor manufacturing process. Furthermore, aluminum oxide can suppress the release of oxygen from the oxide that constitutes the transistor 500. Therefore, aluminum oxide is suitable for use as a protective film for the transistor 500.

[0136] For example, the insulator 512 and the insulator 516 can be made of a material similar to that of the insulator 320. By using a material with a relatively low dielectric constant for these insulators, the parasitic capacitance generated between wirings can be reduced. For example, the insulators 512 and 516 can be made of a silicon oxide film or a silicon oxynitride film.

[0137] A conductor 518, a conductor constituting the transistor 500 (for example, the conductor 503), and the like are embedded in the insulators 510, 512, 514, and 516. The conductor 518 functions as a plug or wiring connected to the capacitor 600, the transistor 550, or the transistor 650. The conductor 518 can be formed using a material similar to that of the conductor 328 and the conductor 330.

[0138] 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 transistor 550 or the transistor 650 can be separated from the transistor 500 by a layer having a barrier property against oxygen, hydrogen, and water, and diffusion of hydrogen from the transistor 550 or the transistor 650 to the transistor 500 can be suppressed.

[0139] Above the insulator 516 is the transistor 500 .

[0140] As shown in Figures 12A and 12B, transistor 500 has conductor 503 arranged so as to be embedded in insulator 514 and insulator 516, insulator 520 arranged on insulator 516 and conductor 503, insulator 522 arranged on insulator 520, insulator 524 arranged on insulator 522, oxide 530a arranged on insulator 524, oxide 530b arranged on oxide 530a, conductors 542a and 542b arranged spaced apart from each other on oxide 530b, insulator 580 arranged on conductors 542a and 542b and having an opening formed therebetween overlapping conductors 542a and 542b, insulator 545 arranged on the bottom and side surfaces of the opening, and conductor 560 arranged on the surface on which insulator 545 is formed.

[0141] 12A and 12B, it is preferable that insulator 544 be disposed between oxide 530a, oxide 530b, conductor 542a, and conductor 542b and insulator 580. It is preferable that conductor 560 have conductor 560a disposed inside insulator 545 and conductor 560b disposed so as to be embedded inside conductor 560a. It is preferable that insulator 574 be disposed on insulator 580, conductor 560, and insulator 545, as shown in FIGS.

[0142] In this specification and the like, the oxide 530a and the oxide 530b may be collectively referred to as the oxide 530. The conductor 542a and the conductor 542b may be collectively referred to as the conductor 542.

[0143] Note that although the transistor 500 has a two-layer structure of the oxide 530a and the oxide 530b in and around a channel formation region, one embodiment of the present invention is not limited to this structure. For example, the oxide 530b may be a single layer or a stack of three or more layers.

[0144] Although the transistor 500 has a two-layer structure, one embodiment of the present invention is not limited to this. For example, the conductor 560 may have a single-layer structure or a stacked structure of three or more layers. The transistor 500 illustrated in FIGS. 11 and 12A is merely an example and is not limited to this structure. An appropriate transistor may be used depending on the circuit configuration, driving method, and the like.

[0145] Here, the conductor 560 functions as the gate electrode of the transistor, and the conductors 542a and 542b function as the source and drain electrodes, 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 arrangement of the conductors 560, 542a, and 542b is selected in a self-aligned manner with respect to the opening of the insulator 580. That is, in the transistor 500, the gate electrode can be positioned between the source and drain electrodes in a self-aligned manner. Therefore, the conductor 560 can be formed without providing a margin for alignment, thereby reducing the area occupied by the transistor 500. This allows for miniaturization and high integration of semiconductor devices.

[0146] 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 between the conductor 560 and the conductor 542b. This improves the switching speed of the transistor 500 and provides high frequency characteristics.

[0147] 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 500 can be controlled by changing the voltage applied to the conductor 503 independently of the voltage applied to the conductor 560. In particular, applying a negative voltage to the conductor 503 can increase the threshold voltage of the transistor 500 and reduce the off-state current. Therefore, applying a negative voltage to the conductor 503 can reduce the drain current when the voltage applied to the conductor 560 is 0 V compared to when no negative voltage is applied.

[0148] The conductor 503 is arranged to overlap the oxide 530 and the conductor 560. In this way, when a voltage 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 a channel formation region formed in the oxide 530 can be covered.

[0149] In this specification, a transistor configuration in which a channel formation region is electrically surrounded by the electric field of a pair of gate electrodes (a first gate electrode and a second gate electrode) is referred to as a surrounded channel (S-channel) structure. In this specification, the S-channel structure is characterized in that the side and periphery of the oxide 530 in contact with the conductors 542a and 542b, which function as source and drain electrodes, are I-type, just like the channel formation region. Furthermore, the side and periphery of the oxide 530 in contact with the conductors 542a and 542b can be I-type, just like the channel formation region, because they are in contact with the insulator 544. In this specification, I-type can be treated as the same as high-purity intrinsic oxide, as described later. The S-channel structure disclosed in this specification differs from the fin type and planar type structures. The S-channel structure enhances resistance to the short-channel effect, or in other words, can provide a transistor that is less susceptible to the short-channel effect.

[0150] 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 500 has a structure in which the conductors 503a and 503b are stacked, one embodiment of 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.

[0151] 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, and copper atoms (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). In this specification, 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 and oxygen.

[0152] 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.

[0153] 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. Note that, although the conductor 503 is illustrated in this embodiment as a stack of the conductors 503a and 503b, the conductor 503 may have a single-layer structure.

[0154] The insulators 520, 522, and 524 function as a second gate insulating film.

[0155] Here, the insulator 524 in contact with the oxide 530 preferably contains more oxygen than the oxygen required for the stoichiometric composition. The oxygen is easily released from the film by heating. In this specification and elsewhere, oxygen released by heating may be referred to as "excess oxygen." In other words, the insulator 524 preferably has a region containing excess oxygen (also referred to as an "excess oxygen region"). By providing such an insulator containing excess oxygen in contact with the oxide 530, oxygen vacancies (V O When hydrogen enters the oxygen vacancy in the oxide 530, the defect (hereinafter referred to as V O H.) functions as a donor and may generate electrons as carriers. In addition, some of the hydrogen may bond with oxygen that is bonded to a metal atom to generate electrons as carriers. Therefore, a transistor using an oxide semiconductor containing a large amount of hydrogen is likely to have normally-on characteristics. Furthermore, hydrogen in an oxide semiconductor is easily moved by stress such as heat or an electric field. Therefore, if an oxide semiconductor contains a large amount of hydrogen, the reliability of the transistor may be reduced. 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 an oxide semiconductor with sufficiently reduced H, it is important to remove impurities such as moisture and hydrogen from the oxide semiconductor (also called "dehydration" or "dehydrogenation treatment") and to supply oxygen to the oxide semiconductor to compensate for oxygen vacancies (also called "oxygenation treatment"). O When an oxide semiconductor in which impurities such as H are sufficiently reduced is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0156] 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.

[0157] Alternatively, 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 The reaction "H → Vo + H" occurs, resulting in dehydrogenation. Some of the generated hydrogen may combine with oxygen to form HO, which may be removed from the oxide 530 or an insulator near the oxide 530. Some of the hydrogen may also be gettered to the conductor 542.

[0158] The microwave treatment is preferably performed using, for example, an apparatus having a power source for generating high-density plasma or an apparatus having a power source for applying RF to the substrate side. For example, high-density oxygen radicals can be generated by using an oxygen-containing gas and high-density plasma, and the oxygen radicals generated by the high-density plasma can be efficiently introduced into the oxide 530 or an insulator near the oxide 530 by applying RF to the substrate side. The microwave treatment is performed at 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 an oxygen flow ratio (O2 / (O2+Ar)) of 50% or less, preferably 10% to 30%.

[0159] During the manufacturing process of the transistor 500, heat treatment is preferably performed with the surface of the oxide 530 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 a nitrogen gas or inert gas atmosphere, 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.

[0160] By subjecting the oxide 530 to oxygen addition treatment, the oxygen vacancies in the oxide 530 can be repaired by the supplied oxygen, in other words, the reaction "Vo + O → null" can be promoted. Furthermore, the supplied oxygen reacts with the hydrogen remaining in the oxide 530, and the hydrogen can be removed as H2O (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.

[0161] 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).

[0162] 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 or the oxide 530 can be suppressed.

[0163] 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 allows for a reduction in gate voltage during transistor operation while maintaining the physical film thickness.

[0164] 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., is difficult for oxygen 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 500.

[0165] 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.

[0166] Furthermore, it is preferable that the insulator 520 be 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 layered structure that is thermally stable and has a high dielectric constant.

[0167] 12A and 12B, the second gate insulating film has a three-layer structure including insulators 520, 522, and 524. However, the second gate insulating film may have a single-layer structure, a two-layer structure, or a four- or more-layer 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.

[0168] The transistor 500 uses a metal oxide functioning as an oxide semiconductor for the oxide 530 including the channel formation region. Note that the oxide semiconductor preferably contains at least one of In and Zn. For example, the oxide 530 may be a metal oxide such as In-M-Zn oxide (wherein 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, or the like).

[0169] The metal oxide functioning as an oxide semiconductor may be formed by a sputtering method or an ALD (Atomic Layer Deposition) method. Note that the metal oxide functioning as an oxide semiconductor will be described in detail in other embodiments.

[0170] 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.

[0171] The oxide 530 has the oxide 530a below the oxide 530b, and thus can suppress the diffusion of impurities from components formed below the oxide 530a to the oxide 530b.

[0172] Preferably, oxide 530 has a configuration of multiple oxide layers with different atomic ratios of each metal atom. Specifically, the atomic ratio of element M among the constituent elements in the metal oxide used for oxide 530a is preferably greater than the atomic ratio of element M among the constituent elements in the metal oxide used for oxide 530b. Furthermore, the atomic ratio of element M to In in the metal oxide used for oxide 530a is preferably greater than the atomic ratio of element M to In in the metal oxide used for oxide 530b. Furthermore, the atomic ratio of In to element M in the metal oxide used for oxide 530b is preferably greater than the atomic ratio of In to element M in the metal oxide used for oxide 530a.

[0173] The energy of the conduction band minimum of the oxide 530a is preferably higher than that of the oxide 530b, or in other words, the electron affinity of the oxide 530a is preferably smaller than that of the oxide 530b.

[0174] Here, the energy level of the conduction band minimum changes gradually at the junction between the oxide 530a and the oxide 530b. In other words, the energy level of the conduction band minimum at the junction between the oxide 530a and the oxide 530b changes continuously or forms a continuous junction. To achieve this, it is preferable to reduce the defect level density of the mixed layer formed at the interface between the oxide 530a and the oxide 530b.

[0175] Specifically, when the oxide 530a and the oxide 530b have a common element (main component) other than oxygen, a mixed layer with a low density of defect states can be formed. For example, when the oxide 530b is an In-Ga-Zn oxide, the oxide 530a may be an In-Ga-Zn oxide, a Ga-Zn oxide, a gallium oxide, or the like.

[0176] In this case, the oxide 530b serves as the main carrier path. By configuring the oxide 530a as described above, the defect state density at the interface between the oxide 530a and the oxide 530b can be reduced. As a result, the influence of interface scattering on carrier conduction is reduced, and the transistor 500 can obtain a high on-state current.

[0177] 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.

[0178] 12A shows the conductor 542a and the conductor 542b as a single layer, they may also be stacked with 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 also be used.

[0179] Other examples include a three-layer structure 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, and 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. Note that a transparent conductive material containing indium oxide, tin oxide, or zinc oxide may also be used.

[0180] 12A, 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 either a source region or a drain region, and the region 543b functions as the other. A channel formation region is formed in the region sandwiched between the regions 543a and 543b.

[0181] 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 density in the region 543a (region 543b) increases, and the region 543a (region 543b) becomes a low-resistance region.

[0182] 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.

[0183] 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.

[0184] 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). Hafnium aluminate is particularly preferable because it has higher heat resistance than hafnium oxide film. Therefore, it is less likely to crystallize during heat treatment in a later process. Note that 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 is not an essential component. It can be designed appropriately depending on the desired transistor characteristics.

[0185] The insulator 544 can prevent impurities such as water and hydrogen contained in the insulator 580 from diffusing into the oxide 530b through the insulator 545. The insulator 580 can also prevent the conductor 560 from being oxidized by excess oxygen.

[0186] The insulator 545 functions as a first gate insulating film. Like the insulator 524, the insulator 545 is preferably formed using an insulator that contains excess oxygen and releases oxygen by heating.

[0187] 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.

[0188] By using an insulator containing excess oxygen as the insulator 545, oxygen can be effectively supplied from the insulator 545 to the channel formation region of the oxide 530b. Similarly to the insulator 524, the concentration of impurities such as water or hydrogen in the insulator 545 is preferably reduced. The thickness of the insulator 545 is preferably 1 nm to 20 nm.

[0189] Furthermore, a metal oxide may be provided between the insulator 545 and the conductor 560 to efficiently supply excess oxygen contained in the insulator 545 to the oxide 530. The metal oxide preferably suppresses oxygen diffusion from the insulator 545 to the conductor 560. By providing a metal oxide that suppresses oxygen diffusion, the diffusion of excess oxygen from the insulator 545 to the conductor 560 is suppressed. That is, 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, any material that can be used for the insulator 544 may be used.

[0190] The insulator 545 may have a layered 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 layered 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 voltage during transistor operation while maintaining the physical film thickness. Furthermore, a layered structure that is thermally stable and has a high dielectric constant can be achieved.

[0191] The conductor 560 functioning as the first gate electrode is shown as having a two-layer structure in FIGS. 12A and 12B, but may have a single-layer structure or a stacked structure of three or more layers.

[0192] 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 (e.g., NO, NO, and the like), and copper atoms. Alternatively, a conductive material that suppresses the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, and the like) is preferably used. The oxygen-suppressing function of the conductor 560a can suppress the oxidation of the conductor 560b due to oxygen contained in the insulator 545, which can reduce the conductivity. Examples of conductive materials that suppress the diffusion of oxygen include tantalum, tantalum nitride, ruthenium, and ruthenium oxide. Alternatively, an oxide semiconductor that can be used for the oxide 530 can be used for the conductor 560a. 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 called an OC (Oxide Conductor) electrode.

[0193] The conductor 560b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. Because 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.

[0194] 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 an excess oxygen region in a later step.

[0195] The insulator 580 preferably has an excess oxygen region. By providing the insulator 580 from which oxygen is released by heating, oxygen in the insulator 580 can be efficiently supplied to the oxide 530. Note that the concentration of impurities such as water or hydrogen in the insulator 580 is preferably reduced.

[0196] 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 to be embedded in the opening of the insulator 580 and the region sandwiched between the conductor 542a and the conductor 542b.

[0197] 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.

[0198] 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 545. By forming the insulator 574 by a sputtering method, an excess oxygen region can be provided in the insulator 545 and the insulator 580. This allows oxygen to be supplied from the excess oxygen region into the oxide 530.

[0199] 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.

[0200] 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.

[0201] An insulator 581 functioning as an interlayer film is preferably provided over the insulator 574. Like the insulator 524, the insulator 581 preferably has a reduced concentration of impurities such as water or hydrogen.

[0202] Furthermore, conductors 540a and 540b are arranged in openings formed in insulators 581, 574, 580, and 544. Conductor 540a and 540b are arranged opposite each other with conductor 560 interposed therebetween. Conductor 540a and 540b have the same configuration as conductors 546 and 548, which will be described later.

[0203] 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.

[0204] In particular, aluminum oxide has a high blocking effect against 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 500 during and after the transistor manufacturing process. Furthermore, aluminum oxide can suppress the release of oxygen from the oxide that constitutes the transistor 500. Therefore, aluminum oxide is suitable for use as a protective film for the transistor 500.

[0205] 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.

[0206] Furthermore, conductors 546, 548, etc. are embedded in insulators 520, 522, 524, 544, 580, 574, 581, 582, and 586.

[0207] The conductor 546 and the conductor 548 function as plugs or wirings that connect to the capacitor 600, the transistor 500, or the transistor 550. The conductor 546 and the conductor 548 can be formed using a material similar to that of the conductor 328 and the conductor 330.

[0208] After the transistor 500 is formed, an opening may be formed to surround the transistor 500, and an insulator with high barrier properties against hydrogen or water may be formed to cover the opening. By surrounding the transistor 500 with the insulator with high barrier properties, it is possible to prevent moisture and hydrogen from entering from the outside. Alternatively, multiple transistors 500 may be collectively surrounded by an insulator with high barrier properties against hydrogen or water. When forming an opening to surround the transistor 500, for example, it is preferable to form an opening that reaches the insulator 522 or the insulator 514 and form the insulator with high barrier properties in contact with the insulator 522 or the insulator 514, because this can serve as part of the manufacturing process of the transistor 500. For example, the insulator with high barrier properties against hydrogen or water may be made of a material similar to that of the insulator 522 or the insulator 514.

[0209] Subsequently, a capacitor 600 is provided above the transistor 650. The capacitor 600 includes a conductor 610, a conductor 620, and an insulator 630.

[0210] A conductor 612 may be provided over the conductor 546 and the conductor 548. The conductor 612 functions as a plug or a wiring connected to the transistor 500. The conductor 610 functions as an electrode of the capacitor 600. Note that the conductor 612 and the conductor 610 can be formed in the same process.

[0211] 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 conductor 612 and the conductor 610. 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.

[0212] In this embodiment, the conductor 612 and the conductor 610 have a single-layer structure, but the present invention is not limited to this structure and may have a stacked 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.

[0213] The conductor 620 is provided so as to overlap with the conductor 610 with the insulator 630 interposed therebetween. Note that the conductor 620 can be formed using a conductive material such as a metal material, an alloy material, or a metal oxide material. It is preferable to use a high-melting-point material such as tungsten or molybdenum that has both heat resistance and conductivity, and tungsten is particularly preferable. Furthermore, when the conductor 620 is formed using the same process as other components such as the conductor, a low-resistance metal material such as Cu (copper) or Al (aluminum) may be used.

[0214] An insulator 640 is provided over the conductor 620 and the insulator 630. The insulator 640 can be provided using a material similar to that of the insulator 320. The insulator 640 may also function as a planarizing film that covers the uneven shape underneath.

[0215] With this structure, miniaturization or high integration can be achieved in a semiconductor device including a transistor including an oxide semiconductor.

[0216] Examples of substrates that can be used in the semiconductor device of one embodiment of the present invention include glass substrates, quartz substrates, sapphire substrates, ceramic substrates, metal substrates (e.g., stainless steel substrates, substrates having stainless steel foil, tungsten substrates, and substrates having tungsten foil), semiconductor substrates (e.g., single-crystal semiconductor substrates, polycrystalline semiconductor substrates, and compound semiconductor substrates), and silicon-on-insulator (SOI) substrates. Plastic substrates that have heat resistance sufficient to withstand the processing temperatures of this embodiment may also be used. Examples of glass substrates include barium borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, and soda-lime glass. Crystallized glass, for example, can also be used.

[0217] Alternatively, flexible substrates, laminated films, paper containing fibrous materials, or base films can be used as the substrate. Examples of flexible substrates, laminated films, and base films include the following: Plastics such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Synthetic resins such as acrylic are also included. Polypropylene, polyester, polyvinyl fluoride, and polyvinyl chloride are also included. Polyamide, polyimide, aramid resin, epoxy resin, inorganic vapor-deposited film, and paper are also included. In particular, transistors manufactured using semiconductor substrates, single-crystal substrates, or SOI substrates can be manufactured to have small size, high current capacity, and minimal variations in characteristics, size, and shape. Constructing a circuit using such transistors can reduce the power consumption of the circuit or increase the circuit integration.

[0218] Alternatively, a flexible substrate may be used as the substrate, and transistors, resistors, and / or capacitors may be formed directly on the flexible substrate. Alternatively, a release layer may be provided between the substrate and the transistors, resistors, and / or capacitors. The release layer can be used to separate a semiconductor device, after it has been partially or entirely completed, from the substrate and transfer it to another substrate. In this case, the transistors, resistors, and / or capacitors can be transferred to a substrate with poor heat resistance or a flexible substrate. The release layer may be, for example, a laminated structure of an inorganic film such as a tungsten film and a silicon oxide film, a structure in which an organic resin film such as polyimide is formed on a substrate, or a silicon film containing hydrogen.

[0219] That is, a semiconductor device may be formed on a certain substrate and then transferred to another substrate. Examples of substrates onto which a semiconductor device may be transferred include, in addition to the substrates on which the above-mentioned transistors can be formed, paper substrates, cellophane substrates, aramid film substrates, polyimide film substrates, stone substrates, wood substrates, cloth substrates (including natural fibers (silk, cotton, hemp), synthetic fibers (nylon, polyurethane, polyester), or recycled fibers (acetate, cupra, rayon, recycled polyester)), leather substrates, and rubber substrates. By using these substrates, it is possible to manufacture semiconductor devices that are flexible, durable, heat-resistant, lightweight, or thin.

[0220] By providing a semiconductor device over a flexible substrate, an increase in weight can be suppressed and a semiconductor device that is less likely to be damaged can be provided.

[0221] <Transistor variation 1> A transistor 500A illustrated in FIGS. 13A to 13C is a modification of the transistor 500 having the structure illustrated in FIGS. 12A and 12B. FIG. 13A is a top view of the transistor 500A, FIG. 13B is a cross-sectional view of the transistor 500A in the channel length direction, and FIG. 13C is a cross-sectional view of the transistor 500A in the channel width direction. Note that some elements are omitted from the top view in FIG. 13A for clarity. Note that the structures illustrated in FIGS. 13A to 13C can also be applied to other transistors, such as the transistor 550, included in the semiconductor device of one embodiment of the present invention.

[0222] 13A to 13C differs from the transistor 500 having the configuration illustrated in FIGS. 12A and 12B in that it includes an insulator 552, an insulator 513, and an insulator 404. The transistor 500A also differs from the transistor 500 in that the insulator 552 is provided in contact with the side surface of the conductor 540a and the insulator 552 is provided in contact with the side surface of the conductor 540b. The transistor 500A also differs from the transistor 500 in that the transistor 500A does not include the insulator 520.

[0223] 13A to 13C, the insulator 513 is provided over the insulator 512. The insulator 404 is provided over the insulator 574 and the insulator 513.

[0224] 13A to 13C , 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 513. As a result, the oxide 530 and the like are isolated from the outside by the insulators 404 and 513.

[0225] The insulators 513 and 404 preferably have a high function of suppressing diffusion of hydrogen (for example, at least one of hydrogen atoms, hydrogen molecules, and the like) 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 513 and 404. This can suppress diffusion of hydrogen and the like into the oxide 530, thereby suppressing deterioration in the characteristics of the transistor 500A. Therefore, the reliability of the semiconductor device of one embodiment of the present invention can be improved.

[0226] 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 made of 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 conductor 540a and the conductor 540b. Furthermore, oxygen contained in the insulator 580 can be suppressed from being absorbed by the conductor 540a and the conductor 540b. As described above, the reliability of the semiconductor device of one embodiment of the present invention can be improved.

[0227] <Transistor variation 2> An example configuration of a transistor 500B will be described using Figures 14A, 14B, and 14C. Figure 14A is a top view of the transistor 500B. Figure 14B is a cross-sectional view of the L1-L2 portion indicated by the dashed-dotted line in Figure 14A. Figure 14C is a cross-sectional view of the W1-W2 portion indicated by the dashed-dotted line in Figure 14A. Note that in the top view of Figure 14A, some elements are omitted for clarity.

[0228] The transistor 500B is a modified example of the transistor 500 and can be substituted for the transistor 500. Therefore, to avoid repetition of explanation, differences from the transistor 500 will be mainly described.

[0229] The conductor 560 functioning as the first gate electrode includes a conductor 560a and a conductor 560b on the conductor 560a. The conductor 560a 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, and copper atoms. Alternatively, the conductor 560a is preferably made of a conductive material that has the function of suppressing the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.).

[0230] The conductor 560a has the function of suppressing oxygen diffusion, which improves the material selectivity of the conductor 560b. In other words, the presence of the conductor 560a suppresses oxidation of the conductor 560b, preventing a decrease in conductivity.

[0231] Furthermore, it is preferable to provide an insulator 544 so as to cover the top surface and side surfaces of the conductor 560 and the side surfaces of the insulator 545. Note that the insulator 544 is preferably made of an insulating material that has a function of suppressing the diffusion of impurities such as water or hydrogen and oxygen. For example, it is preferable to use aluminum oxide or hafnium oxide. Other examples that can be used include metal oxides such as magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, and tantalum oxide, silicon nitride oxide, and silicon nitride.

[0232] Providing the insulator 544 can suppress oxidation of the conductor 560. Furthermore, including the insulator 544 can suppress diffusion of impurities such as water and hydrogen contained in the insulator 580 into the transistor 500B.

[0233] In the transistor 500B, the conductor 560 overlaps part of the conductor 542a and part of the conductor 542b, and therefore the parasitic capacitance of the transistor 500B is likely to be larger than that of the transistor 500. Therefore, the operating frequency of the transistor 500B tends to be lower than that of the transistor 500. However, the transistor 500B has higher productivity than the transistor 500 because it does not require a step of forming an opening in the insulator 580 or the like and filling it with the conductor 560, the insulator 545, or the like.

[0234] The structures, configurations, methods, and the like described in this embodiment can be used in appropriate combination with structures, configurations, methods, and the like described in other embodiments.

[0235] (Fourth embodiment) In this embodiment, an oxide semiconductor, which is a type of metal oxide, will be described.

[0236] The metal oxide preferably contains at least indium or zinc. It is particularly preferable that it contains indium and zinc. It is also preferable that it contains aluminum, gallium, yttrium, tin, or the like in addition to these. It may also contain one or more elements selected from boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, cobalt, and the like.

[0237] <Classification of crystal structures> First, classification of crystal structures in oxide semiconductors will be described with reference to Fig. 15A. Fig. 15A is a diagram illustrating classification of crystal structures of oxide semiconductors, typically IGZO (a metal oxide containing In, Ga, and Zn).

[0238] As shown in FIG. 15A, oxide semiconductors are broadly classified into "amorphous," "crystalline," and "crystal." "Amorphous" includes completely amorphous. "Crystalline" includes c-axis-aligned crystalline (CAAC), nanocrystalline (nc), and cloud-aligned composite (CAC) (excluding single crystal and polycrystal). "Crystalline" excludes single crystal, polycrystal, and completely amorphous. "Crystalline" includes single crystal and polycrystal.

[0239] The structure within the bold frame in Figure 15A is an intermediate state between "amorphous" and "crystal," and is a structure that belongs to a new boundary region (new crystalline phase). In other words, this structure can be described as a structure that is completely different from the energetically unstable "amorphous" or "crystal."

[0240] The crystalline structure of a film or substrate can be evaluated using X-ray diffraction (XRD) spectroscopy. Figure 15B shows the XRD spectrum obtained by GIXD (Grazing-Incidence XRD) measurement of a CAAC-IGZO film classified as "Crystalline." The GIXD method is also known as the thin-film method or the Seemann-Bohlin method. Hereinafter, the XRD spectrum obtained by GIXD measurement shown in Figure 15B will be simply referred to as the XRD spectrum. The composition of the CAAC-IGZO film shown in Figure 15B is approximately In:Ga:Zn = 4:2:3 [atomic ratio]. The thickness of the CAAC-IGZO film shown in Figure 15B is 500 nm.

[0241] As shown in Figure 15B, a clear peak indicating crystallinity is detected in the XRD spectrum of the CAAC-IGZO film. Specifically, a peak indicating c-axis orientation is detected near 2θ = 31° in the XRD spectrum of the CAAC-IGZO film. Note that, as shown in Figure 15B, the peak near 2θ = 31° is asymmetric with respect to the angle at which the peak intensity is detected.

[0242] The crystalline structure of a film or substrate can be evaluated by a diffraction pattern (also called a nanobeam electron diffraction pattern) observed using nanobeam electron diffraction (NBED). The diffraction pattern of a CAAC-IGZO film is shown in Figure 15C. Figure 15C shows a diffraction pattern observed using NBED, in which an electron beam is incident parallel to the substrate. The composition of the CAAC-IGZO film shown in Figure 15C is approximately In:Ga:Zn = 4:2:3 [atomic ratio]. In nanobeam electron diffraction, electron diffraction is performed using a probe diameter of 1 nm.

[0243] As shown in FIG. 15C, multiple spots indicating c-axis orientation are observed in the diffraction pattern of the CAAC-IGZO film.

[0244] <<Oxide semiconductor structure>> Note that oxide semiconductors may be classified differently from those shown in FIG. 15A when focusing on their crystal structures. For example, oxide semiconductors are divided into single-crystal oxide semiconductors and other non-single-crystal oxide semiconductors. Examples of non-single-crystal oxide semiconductors include the above-mentioned CAAC-OS and nc-OS. Non-single-crystal oxide semiconductors include polycrystalline oxide semiconductors, amorphous-like oxide semiconductors (a-like OSs), amorphous oxide semiconductors, and the like.

[0245] Here, the above-mentioned CAAC-OS, nc-OS, and a-like OS will be described in detail.

[0246] [CAAC-OS] CAAC-OS is an oxide semiconductor having multiple crystalline regions, each with its c-axis aligned in a specific direction. The specific direction can be the thickness direction of the CAAC-OS film, the normal direction to the surface on which the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film. A crystalline region is a region with periodic atomic arrangement. If the atomic arrangement is considered as a lattice arrangement, a crystalline region can also be a region with a uniform lattice arrangement. Furthermore, CAAC-OS has a region where multiple crystalline regions are connected in the ab-plane direction, and the region may have distortion. Note that distortion refers to a location where the lattice arrangement changes between a region with a uniform lattice arrangement and a region with a different uniform lattice arrangement in the region where multiple crystalline regions are connected. In other words, CAAC-OS is an oxide semiconductor with a c-axis aligned but no clear orientation in the ab-plane direction.

[0247] Each of the multiple crystalline regions is composed of one or more minute crystals (crystals with a maximum diameter of less than 10 nm). When a crystalline region is composed of one minute crystal, the maximum diameter of the crystalline region is less than 10 nm. When a crystalline region is composed of many minute crystals, the size of the crystalline region may be several tens of nm.

[0248] In addition, in an In-M-Zn oxide (wherein element M is one or more elements selected from aluminum, gallium, yttrium, tin, titanium, etc.), the CAAC-OS tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium (In) and oxygen (hereinafter referred to as an In layer) and a layer containing element M, zinc (Zn), and oxygen (hereinafter referred to as an (M, Zn) layer) are stacked. Note that indium and element M are mutually substituted. Therefore, the (M, Zn) layer may contain indium. Furthermore, the In layer may contain element M. Furthermore, the In layer may contain Zn. The layered structure is observed as a lattice image in a high-resolution TEM image, for example.

[0249] When the CAAC-OS film is subjected to structural analysis using, for example, an XRD apparatus, a peak indicating c-axis orientation is detected at or near 2θ=31° in out-of-plane XRD measurement using θ / 2θ scan. Note that the position of the peak indicating c-axis orientation (2θ value) may vary depending on the type and composition of the metallic elements constituting the CAAC-OS.

[0250] Furthermore, for example, in the electron diffraction pattern of the CAAC-OS film, multiple bright spots are observed, and the spots are observed at positions that are point-symmetric with respect to the spot of the incident electron beam that has passed through the sample (also called the direct spot).

[0251] When the crystalline region is observed from the specific direction, the lattice arrangement within the crystalline region is basically a hexagonal lattice, but the unit cell is not necessarily a regular hexagon and may be non-regular hexagonal. Furthermore, the distortion may have a pentagonal, heptagonal, or other lattice arrangement. In the CAAC-OS, no clear grain boundaries are observed even near the distortion. This indicates that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is thought to be because the CAAC-OS can tolerate distortion due to the lack of close-packed oxygen atom arrangement in the ab-plane direction and the change in interatomic bond distance caused by metal atom substitution.

[0252] A crystal structure with clear grain boundaries is called polycrystalline. Grain boundaries act as recombination centers, trapping carriers and potentially reducing the on-state current and field-effect mobility of transistors. Therefore, CAAC-OS, which lacks clear grain boundaries, is one of the crystalline oxides with a crystal structure suitable for use in transistor semiconductor layers. Zn is preferred for use in CAAC-OS. For example, In-Zn oxide and In-Ga-Zn oxide are suitable because they can suppress the generation of grain boundaries more effectively than In oxide.

[0253] CAAC-OS is an oxide semiconductor with high crystallinity and no clear grain boundaries. Therefore, it can be said that the CAAC-OS is less susceptible to a decrease in electron mobility due to grain boundaries. Furthermore, since the crystallinity of an oxide semiconductor can be reduced by impurities or defects, the CAAC-OS can 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, the CAAC-OS is stable even under high temperatures (so-called thermal budget) during the manufacturing process. Therefore, using a CAAC-OS for an OS transistor can increase the flexibility of the manufacturing process.

[0254] [nc-OS] The nc-OS has periodic atomic arrangement in a microscopic region (e.g., a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In other words, the nc-OS has microcrystalline structures. The size of the microcrystalline structures is, for example, 1 nm to 10 nm, particularly 1 nm to 3 nm, and therefore these microcrystalline structures are also called nanocrystalline structures. Furthermore, the nc-OS exhibits no regularity in the crystal orientation between different nanocrystalline structures. Therefore, the entire film lacks orientation. Therefore, depending on the analytical method, the nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor. For example, when a structural analysis of an nc-OS film is performed using an XRD system, no peaks indicating crystallinity are detected in out-of-plane XRD measurements using θ / 2θ scanning. Furthermore, when an nc-OS film is subjected to electron diffraction (also known as selected-area electron diffraction) using an electron beam with a probe diameter larger than that of nanocrystalline structures (e.g., 50 nm or larger), a halo-like diffraction pattern is observed. On the other hand, when electron diffraction (also called nanobeam electron diffraction) is performed on an nc-OS film using an electron beam with a probe diameter close to or smaller than the size of the nanocrystals (for example, 1 nm to 30 nm), an electron diffraction pattern can be obtained in which multiple spots are observed within a ring-shaped region centered on the direct spot.

[0255] [a-like OS] 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 CAAC-OS. Furthermore, the a-like OS has a higher hydrogen concentration in the film than the nc-OS and CAAC-OS.

[0256] <<Oxide semiconductor structure>> Next, the above-mentioned CAC-OS will be described in detail, which relates to the material composition.

[0257] [CAC-OS] CAC-OS is a material structure in which elements constituting a metal oxide are unevenly distributed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or a similar size range. Hereinafter, a metal oxide in which one or more metal elements are unevenly distributed and the regions containing the metal elements are mixed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or a similar size range, is also referred to as a mosaic or patch state.

[0258] Furthermore, CAC-OS has a mosaic structure in which the material is separated into first and second regions, and the first regions are distributed throughout the film (hereinafter also referred to as a cloud structure). That is, CAC-OS is a composite metal oxide having a structure in which the first and second regions are mixed.

[0259] Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In-Ga-Zn oxide are denoted as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS in the In-Ga-Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. The second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is a region where [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. The second region is a region where [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

[0260] Specifically, the first region is a region whose main component is indium oxide, indium zinc oxide, or the like. The second region is a region whose main component is gallium oxide, gallium zinc oxide, or the like. In other words, the first region can be rephrased as a region whose main component is In. The second region can be rephrased as a region whose main component is Ga.

[0261] It should be noted that there are cases where a clear boundary between the first region and the second region cannot be observed.

[0262] For example, in the case of CAC-OS in In-Ga-Zn oxide, EDX mapping obtained using EDX (Energy Dispersive X-ray spectroscopy) confirms that the CAC-OS has a structure in which a region mainly composed of In (first region) and a region mainly composed of Ga (second region) are unevenly distributed and mixed.

[0263] When CAC-OS is used in a transistor, the conductivity due to the first region and the insulating property due to the second region act in a complementary manner, thereby providing the CAC-OS with a switching function (the ability to turn on and off). In other words, CAC-OS has a conductive function in part of the material and an insulating function in part of the material, and the material as a whole functions as a semiconductor. By separating the conductive function from the insulating function, both functions can be maximized. Therefore, by using CAC-OS in a transistor, a high on-current (I on ), high field-effect mobility (μ), and good switching behavior can be achieved.

[0264] 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, a CAC-OS, an nc-OS, and a CAAC-OS.

[0265] <Transistors containing oxide semiconductors> Next, a case where the oxide semiconductor is used in a transistor will be described.

[0266] By using the oxide semiconductor for a transistor, a transistor with high field-effect mobility and high reliability can be realized.

[0267] For the transistor, an oxide semiconductor with a low carrier concentration is preferably used. For example, the carrier concentration of the oxide semiconductor is 1×10 17 cm -3 Less than 1 × 10 15 cm -3 or less, more preferably 1 × 10 13 cm -3 Less than 1×10, more preferably 11 cm -3 or less, more preferably 1 × 10 10 cm -3 Less than 1 x 10 -9 cm-3 The above is the case. Note that in order to reduce the carrier concentration of an 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 or substantially highly purified intrinsic oxide semiconductor. Note that an oxide semiconductor having a low carrier concentration may also be referred to as a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor.

[0268] 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.

[0269] 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.

[0270] 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.

[0271] <Impurities> Here, the influence of each impurity in an oxide semiconductor will be described.

[0272] 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 17atoms / cm 3 The following applies.

[0273] Furthermore, when an oxide semiconductor contains an alkali metal or alkaline earth metal, defect levels 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, when the concentration of the alkali metal or alkaline earth metal in the oxide semiconductor obtained by SIMS is 1×10 18 atoms / cm 3 Less than or equal to 2 x 10 16 atoms / cm 3 Do the following:

[0274] Furthermore, when nitrogen is contained in an oxide semiconductor, electrons serving as carriers are generated, the carrier concentration increases, and the 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. Alternatively, when nitrogen is contained in an oxide semiconductor, trap states may be formed. As a result, the electrical characteristics of the transistor may become unstable. For this reason, the nitrogen concentration in the oxide semiconductor obtained by SIMS is set to 5×10 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 Do the following:

[0275] Furthermore, hydrogen contained in an oxide semiconductor may react with oxygen bonded to a metal atom to form water, which may form 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, the hydrogen concentration in an oxide semiconductor measured 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 Make it less than.

[0276] When an oxide semiconductor with sufficiently reduced impurities is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0277] The structures, configurations, methods, and the like described in this embodiment can be used in appropriate combination with structures, configurations, methods, and the like described in other embodiments.

[0278] (Embodiment 5) In this embodiment, an application example of the above-described semiconductor device will be described.

[0279] [Semiconductor wafers, chips] 16A illustrates a top view of a substrate 711 before dicing. The substrate 711 can be, for example, a semiconductor substrate (also referred to as a "semiconductor wafer"). A plurality of circuit regions 712 are provided over the substrate 711. The circuit region 712 can be provided with a semiconductor device according to one embodiment of the present invention, other functional circuits, or the like.

[0280] Each of the multiple circuit regions 712 is surrounded by an isolation region 713. Separation lines (also called "dicing lines") 714 are set at positions overlapping the isolation regions 713. By cutting the substrate 711 along the separation lines 714, chips 715 including the circuit regions 712 can be cut out from the substrate 711. An enlarged view of the chips 715 is shown in FIG. 16B.

[0281] Furthermore, a conductor or a semiconductor layer may be provided in the separation region 713. By providing a conductor or a semiconductor layer in the separation region 713, ESD that may occur during the dicing process can be mitigated, and a decrease in the yield of the dicing process can be prevented. Furthermore, the dicing process is generally performed while pure water, in which carbon dioxide or the like is dissolved to reduce the resistivity, is flowed over the cutting area for the purposes of cooling the substrate, removing shavings, preventing static electricity, etc. By providing a conductor or a semiconductor layer in the separation region 713, the amount of pure water used can be reduced. This can reduce the production cost of the semiconductor device. Furthermore, the productivity of the semiconductor device can be increased.

[0282] It is preferable to use a material having a band gap of 2.5 eV to 4.2 eV, preferably 2.7 eV to 3.5 eV, for the semiconductor layer provided in the separation region 713. Use of such a material allows the accumulated charge to be slowly discharged, thereby suppressing the sudden movement of charge due to ESD and making it difficult for electrostatic breakdown to occur.

[0283] [Electronic Components] An example of applying chip 715 to an electronic component will be described with reference to Fig. 17. The electronic component is also called a semiconductor package or an IC package. Electronic components have multiple standards and names depending on the terminal lead-out direction and terminal shape.

[0284] The electronic component is completed by combining the semiconductor device shown in the above embodiment with components other than the semiconductor device in an assembly process (post-process).

[0285] The following describes the post-process using the flowchart shown in Figure 17A. After the element substrate having the semiconductor device shown in the above embodiment is completed in the pre-process, a "backside grinding process" is performed to grind the backside of the element substrate (the surface on which the semiconductor device, etc. is not formed) (step S721). By thinning the element substrate by grinding, warping of the element substrate can be reduced, and electronic components can be made smaller.

[0286] Next, a "dicing process" is performed to separate the element substrate into a plurality of chips (chips 715) (step S722). Then, a "die bonding process" is performed to individually pick up the separated chips and bond them onto a lead frame (step S723). The bonding between the chip and the lead frame in the die bonding process is performed using a method appropriate for the product, such as bonding with resin or bonding with tape. It is also possible to bond the chip onto an interposer substrate instead of a lead frame.

[0287] Next, a "wire bonding process" is performed (step S724), in which the leads of the lead frame and the electrodes on the chip are electrically connected with thin metal wires. Silver wires or gold wires can be used for the thin metal wires. The wire bonding can be ball bonding or wedge bonding.

[0288] The wire-bonded chip is then subjected to the "encapsulation process (molding process)" in which it is encapsulated with epoxy resin or the like (step S725). The encapsulation process fills the interior of the electronic component with resin, protecting the circuitry built into the chip and the wires connecting the chip to the leads from external mechanical forces, and also reducing the deterioration of characteristics (reduced reliability) due to moisture and dust.

[0289] Next, a "lead plating process" is performed to plate the leads of the lead frame (step S726). Plating prevents the leads from rusting, allowing for more reliable soldering when mounting the device on a printed circuit board later. Next, a "forming process" is performed to cut and form the leads (step S727).

[0290] Next, a "marking process" is carried out to print (mark) the surface of the package (step S728), and then an "inspection process" (step S729) is carried out to check whether the external shape is good or not, whether there are any malfunctions, etc., and the electronic component is completed.

[0291] 17B shows a perspective schematic diagram of a completed electronic component. In FIG. 17B, a perspective schematic diagram of a QFP (Quad Flat Package) is shown as an example of an electronic component. Electronic component 750 shown in FIG. 17B includes leads 755 and a semiconductor device 753. The semiconductor device described in the above embodiment can be used as semiconductor device 753.

[0292] 17B is mounted on, for example, a printed circuit board 752. A plurality of such electronic components 750 are combined and electrically connected on the printed circuit board 752 to complete a board (mounted board 754) on which electronic components are mounted. The completed mounted board 754 is used in electronic devices and the like.

[0293] [Electronic equipment] Next, examples of electronic devices including the semiconductor device or the electronic component according to one embodiment of the present invention will be described.

[0294] Examples of electronic devices using a semiconductor device or electronic component according to one embodiment of the present invention include display devices such as televisions and monitors, lighting devices, desktop or notebook personal computers, word processors, and DVD (Digital Versatile Disc) players. Examples of such devices include image playback devices that play back still images or videos stored on recording media such as CDs, portable CD players, radios, tape recorders, headphone stereos, stereos, table clocks, wall clocks, cordless telephone handsets, transceivers, mobile phones, car phones, portable game consoles, tablet terminals, large game consoles such as pachinko machines, calculators, portable information terminals (also referred to as "mobile information terminals"), electronic organizers, e-book terminals, electronic translators, voice input devices, video cameras, digital still cameras, electric shavers, high-frequency heating devices such as microwave ovens, electric rice cookers, electric washing machines, electric vacuum cleaners, water heaters, electric fans, hair dryers, air conditioning equipment such as air conditioners, humidifiers, and dehumidifiers, dishwashers, dish dryers, clothes dryers, futon dryers, electric refrigerators, electric freezers, electric refrigerator-freezers, DNA storage freezers, flashlights, tools such as chainsaws, smoke detectors, and medical equipment such as dialysis machines. Further examples include industrial equipment such as guide lights, traffic lights, belt conveyors, elevators, escalators, industrial robots, power storage systems, and power storage devices for power leveling and smart grids.

[0295] Mobile bodies propelled by electric motors using power from power storage devices are also included in the category of electronic devices. Examples of such mobile bodies include electric vehicles (EVs), hybrid electric vehicles (HEVs) that combine an internal combustion engine with an electric motor, plug-in hybrid electric vehicles (PHEVs), tracked vehicles in which the tires and wheels of these vehicles are replaced with tracks, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, golf carts, small or large ships, submarines, helicopters, aircraft, rockets, artificial satellites, space probes, planetary probes, and spaceships.

[0296] A semiconductor device or electronic component according to one embodiment of the present invention can be used in a communication device or the like built into these electronic devices.

[0297] The electronic device may have sensors (including those that can measure force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared light), etc.

[0298] Electronic devices can have various functions, such as a function to display various information (still images, videos, text images, etc.) on a display unit, a touch panel function, a function to display a calendar, date, or time, a function to execute various software (programs), a wireless communication function, and a function to read out programs or data recorded on a recording medium.

[0299] 18 and 19A to 19F illustrate examples of electronic devices. In FIG. 18, a display device 8000 is an example of an electronic device including a semiconductor device 8004 according to one embodiment of the present invention. Specifically, the display device 8000 corresponds to a display device for receiving TV broadcasts and includes a housing 8001, a display portion 8002, a speaker portion 8003, a semiconductor device 8004, a power storage device 8005, and the like. The semiconductor device 8004 according to one embodiment of the present invention is provided inside the housing 8001. The semiconductor device 8004 can store control information, a control program, and the like. The semiconductor device 8004 has a communication function, allowing the display device 8000 to function as an IoT device. The display device 8000 can receive power from a commercial power source or use power stored in the power storage device 8005.

[0300] The display unit 8002 can be a liquid crystal display device, a light-emitting display device in which each pixel has a light-emitting element such as an organic EL element, an electrophoretic display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), or other display device.

[0301] The display device includes all display devices for displaying information, such as those for receiving TV broadcasts, those for personal computers, and those for displaying advertisements.

[0302] 18 , a stationary lighting device 8100 is an example of an electronic device including a semiconductor device 8103 according to one embodiment of the present invention. Specifically, the lighting device 8100 includes a housing 8101, a light source 8102, a semiconductor device 8103, a power storage device 8105, and the like. FIG. 18 illustrates an example in which the semiconductor device 8103 is provided inside a ceiling 8104 on which the housing 8101 and the light source 8102 are installed; however, the semiconductor device 8103 may be provided inside the housing 8101. The semiconductor device 8103 can store information such as the light emission luminance of the light source 8102, a control program, and the like. The semiconductor device 8103 has a communication function, which allows the lighting device 8100 to function as an IoT device. The lighting device 8100 can receive power from a commercial power source or use power stored in a power storage device.

[0303] Note that although the lighting device 8100 in FIG. 18 is a stationary lighting device provided on the ceiling 8104, the semiconductor device according to one embodiment of the present invention can also be used in a stationary lighting device provided on a side wall 8405, a floor 8406, a window 8407, or the like, other than the ceiling 8104, or can also be used in a tabletop lighting device.

[0304] Furthermore, an artificial light source that artificially obtains light using electric power can be used as the light source 8102. Specifically, examples of the artificial light source include discharge lamps such as incandescent lamps and fluorescent lamps, and light-emitting elements such as LEDs and organic EL elements.

[0305] In FIG. 18 , an air conditioner including an indoor unit 8200 and an outdoor unit 8204 is an example of an electronic device including a semiconductor device 8203 according to one embodiment of the present invention. Specifically, the indoor unit 8200 includes a housing 8201, an air outlet 8202, a semiconductor device 8203, a power storage device 8205, and the like. Although FIG. 18 illustrates the case where the semiconductor device 8203 is provided in the indoor unit 8200, the semiconductor device 8203 may be provided in the outdoor unit 8204. Alternatively, the semiconductor device 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The semiconductor device 8203 can store control information, a control program, and the like for the air conditioner. The semiconductor device 8203 has a communication function, allowing the air conditioner to function as an IoT device. The air conditioner can receive power from a commercial power source or use power stored in the power storage device 8205.

[0306] Note that although FIG. 18 illustrates an example of a separate air conditioner including an indoor unit and an outdoor unit, the semiconductor device according to one embodiment of the present invention can also be used in an integrated air conditioner in which the functions of the indoor unit and the outdoor unit are combined in one housing.

[0307] 18 , an electric refrigerator-freezer 8300 is an example of an electronic device including a semiconductor device 8304 according to one embodiment of the present invention. Specifically, the electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator door 8302, a freezer door 8303, a semiconductor device 8304, a power storage device 8305, and the like. In FIG. 18 , the power storage device 8305 is provided inside the housing 8301. The semiconductor device 8304 can store control information, a control program, and the like for the electric refrigerator-freezer 8300. The semiconductor device 8304 has a communication function, which allows the electric refrigerator-freezer 8300 to function as an IoT device. The electric refrigerator-freezer 8300 can receive power from a commercial power source or use power stored in the power storage device 8305.

[0308] 19A shows an example of a wristwatch-type portable information terminal. The portable information terminal 6100 includes a housing 6101, a display portion 6102, a band 6103, operation buttons 6105, and the like. The portable information terminal 6100 also includes a secondary battery and a semiconductor device or electronic component according to one embodiment of the present invention. By using the semiconductor device or electronic component according to one embodiment of the present invention in the portable information terminal 6100, the portable information terminal 6100 can function as an IoT device.

[0309] 19B shows an example of a mobile phone. A mobile information terminal 6200 includes a display portion 6202 incorporated in a housing 6201, operation buttons 6203, a speaker 6204, a microphone 6205, and the like.

[0310] The portable information terminal 6200 also includes a fingerprint sensor 6209 in an area overlapping with the display portion 6202. The fingerprint sensor 6209 may be an organic optical sensor. Since fingerprints are different for each person, personal authentication can be performed by acquiring a fingerprint pattern with the fingerprint sensor 6209. Light emitted from the display portion 6202 can be used as a light source for acquiring the fingerprint pattern with the fingerprint sensor 6209.

[0311] The portable information terminal 6200 includes a secondary battery and a semiconductor device or electronic component according to one embodiment of the present invention. When the portable information terminal 6200 includes the semiconductor device or electronic component according to one embodiment of the present invention, the portable information terminal 6200 can function as an IoT device.

[0312] 19C shows an example of a cleaning robot. The cleaning robot 6300 has a display unit 6302 arranged on the top surface of a housing 6301, a plurality of cameras 6303 arranged on the side, a brush 6304, an operation button 6305, various sensors, and the like. Although not shown, the cleaning robot 6300 is provided with tires, a suction port, and the like. The cleaning robot 6300 can move by itself, detect dust 6310, and suck up the dust from a suction port arranged on the bottom surface.

[0313] For example, the cleaning robot 6300 can analyze an image captured by the camera 6303 and determine whether or not there is an obstacle such as a wall, furniture, or a step. Furthermore, if an object that may become entangled in the brush 6304, such as a wire, is detected through image analysis, the cleaning robot 6300 can stop rotation of the brush 6304. The cleaning robot 6300 includes a secondary battery and a semiconductor device or electronic component according to one embodiment of the present invention. By using the semiconductor device or electronic component according to one embodiment of the present invention in the cleaning robot 6300, the cleaning robot 6300 can function as an IoT device.

[0314] Fig. 19D shows an example of a robot. The robot 6400 shown in Fig. 19D includes a computing device 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6407, and a movement mechanism 6408.

[0315] The microphone 6402 has a function of detecting the user's speaking voice, environmental sounds, etc. The speaker 6404 has a function of emitting sound. The robot 6400 can communicate with the user using the microphone 6402 and the speaker 6404.

[0316] The display unit 6405 has a function of displaying various information. The robot 6400 can display information desired by the user on the display unit 6405. The display unit 6405 may be equipped with a touch panel. The display unit 6405 may also be a detachable information terminal, which can be installed in a fixed position on the robot 6400 to enable charging and data transfer.

[0317] The upper camera 6403 and the lower camera 6406 have a function of capturing images of the periphery of the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of an obstacle in the moving direction when the robot 6400 moves forward using the moving mechanism 6408. The robot 6400 can recognize the surrounding environment and move safely using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407. The light-emitting device of one embodiment of the present invention can be used for the display portion 6405.

[0318] The robot 6400 includes a secondary battery and a semiconductor device or electronic component according to one embodiment of the present invention. By using the semiconductor device or electronic component according to one embodiment of the present invention in the robot 6400, the robot 6400 can function as an IoT device.

[0319] Fig. 19E shows an example of an aircraft. Aircraft 6500 shown in Fig. 19E has propeller 6501, camera 6502, battery 6503, etc., and has the function of flying autonomously.

[0320] For example, image data captured by the camera 6502 is stored in the electronic component 6504. The electronic component 6504 can analyze the image data and detect the presence or absence of obstacles when moving. The electronic component 6504 can also estimate the remaining battery charge from a change in the storage capacity of the battery 6503. The flying object 6500 includes a semiconductor device or electronic component according to one embodiment of the present invention therein. By using the semiconductor device or electronic component according to one embodiment of the present invention in the flying object 6500, the flying object 6500 can function as an IoT device.

[0321] 19F illustrates an example of an automobile. The automobile 7160 includes an engine, tires, brakes, a steering device, a camera, and the like. The automobile 7160 includes a semiconductor device or an electronic component according to one embodiment of the present invention inside. By using the semiconductor device or the electronic component according to one embodiment of the present invention in the automobile 7160, the automobile 7160 can function as an IoT device.

[0322] The structures, configurations, methods, and the like described in this embodiment can be used in appropriate combination with structures, configurations, methods, and the like described in other embodiment modes.

[0323] (Embodiment 6) A normally-off CPU (also referred to as an "Noff-CPU") can be realized using the OS transistor described in this specification. Note that an Noff-CPU is an integrated circuit including a normally-off transistor that is off (also referred to as off) even when the gate voltage is 0 V.

[0324] The Noff-CPU can stop the power supply to circuits within the Noff-CPU that are not in operation, putting those circuits into a standby state. When the power supply is stopped and the circuit is in a standby state, no power is consumed. Therefore, the Noff-CPU can minimize power consumption. Furthermore, the Noff-CPU can retain information necessary for operation, such as setting conditions, for a long period of time even if the power supply is stopped. To return from the standby state, it is only necessary to resume the power supply to the circuit, and there is no need to rewrite setting conditions, etc. In other words, it is possible to quickly return from the standby state. In this way, the Noff-CPU can reduce power consumption without significantly reducing operating speed.

[0325] The Noff-CPU can be suitably used in small-scale systems such as IoT terminal devices (also called "endpoint microcomputers") 803 in the field of IoT (Internet of Things).

[0326] Figure 20 shows the hierarchical structure of an IoT network and trends in required specifications. In Figure 20, power consumption 804 and processing performance 805 are shown as required specifications. The hierarchical structure of an IoT network is broadly divided into an upper cloud field 801 and a lower embedded field 802. The cloud field 801 includes, for example, servers. The embedded field 802 includes, for example, machines, industrial robots, in-vehicle devices, and home appliances.

[0327] The higher the layer, the more important it is to have high processing performance rather than low power consumption. Therefore, in the cloud field 801, high-performance CPUs, high-performance GPUs, large-scale SoCs, and the like are used. Furthermore, the lower the layer, the more important it is to have low power consumption rather than high processing performance, and the number of devices increases explosively. A semiconductor device according to one embodiment of the present invention can be suitably used for a communication device of an IoT terminal device that requires low power consumption.

[0328] The term "endpoint" refers to the terminal area of ​​the embedded field 802. Devices used as endpoints include, for example, microcomputers used in factories, home appliances, infrastructure, agriculture, and the like.

[0329] FIG. 21 illustrates an image of factory automation as an application example of an endpoint microcontroller. A factory 884 is connected to a cloud 883 via an Internet line. The cloud 883 is connected to a home 881 and an office 882 via the Internet line. The Internet line may be a wired communication system or a wireless communication system. For example, in the case of a wireless communication system, a semiconductor device according to one embodiment of the present invention may be used in a communication device to perform wireless communication in accordance with a communication standard such as a fourth-generation mobile communication system (4G) or a fifth-generation mobile communication system (5G). The factory 884 may be connected to factories 885 and 886 via the Internet line.

[0330] The factory 884 has a master device (control device) 831. The master device 831 has a function of connecting to a cloud 883 and transmitting and receiving information. The master device 831 is also connected to a plurality of industrial robots 842 included in an IoT terminal device 841 via an M2M (Machine to Machine) interface 832. As the M2M interface 832, for example, industrial Ethernet ("Ethernet" is a registered trademark), which is a type of wired communication method, or local 5G, which is a type of wireless communication method, may be used.

[0331] A factory manager can connect to a factory 884 via a cloud 883 from a home 881 or office 882 to know the operating status, etc. He can also check for incorrect or missing items, give instructions on where to put them, measure takt time, etc.

[0332] In recent years, the introduction of IoT into factories has been progressing worldwide under the name of "smart factories." In smart factory cases, there have been reported cases where endpoint microcomputers are used not only for simple inspection and auditing but also for fault detection and anomaly prediction.

[0333] Small-scale systems such as endpoint microcontrollers often consume little power overall during operation, so the power saving effect of a Noff-CPU during standby operation is significant. On the other hand, in the embedded field of IoT, quick response is sometimes required, and the use of a Noff-CPU makes it possible to achieve fast recovery from standby operation.

[0334] The structures, configurations, methods, and the like described in this embodiment can be used in appropriate combination with structures, configurations, methods, and the like described in other embodiments.

[0335] (Notes regarding the present specification) The above-described embodiment and each configuration in the embodiment will be described below with additional notes.

[0336] The configurations shown in each embodiment can be combined with the configurations shown in other embodiments as appropriate 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.

[0337] 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.

[0338] 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.

[0339] 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.

[0340] 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.

[0341] 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.

[0342] 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.

[0343] 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.

[0344] 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.

[0345] 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.

[0346] 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.

[0347] 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.

[0348] 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.

[0349] 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.

[0350] 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.

[0351] 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]

[0352] 10: wireless communication device, 100: semiconductor device, 101: current-voltage conversion unit, 102: current switch unit, 103: voltage-current conversion unit, 111: transistor, 112: semiconductor layer, 121: transistor, 122: semiconductor layer

Claims

1. a current-voltage conversion unit; a current switch unit; a voltage-current converter; A control unit; a voltage holding unit, the current switch unit includes a first transistor, the voltage-current converter includes a second transistor; the control unit includes a third transistor; the voltage holding unit has an inductor, the first transistor has an oxide semiconductor in a channel formation region; the second transistor has a nitride semiconductor in a channel formation region, the third transistor has silicon in a channel formation region; the first transistor is provided in a layer above a layer in which the second transistor and the third transistor are provided; the inductor is provided in a layer above the layer in which the first transistor is provided; Semiconductor device.

2. a current-voltage conversion unit; a current switch unit; a voltage-current converter; A control unit; a voltage holding unit, the current switch unit includes a first transistor, the voltage-current converter includes a second transistor; the control unit includes a third transistor; the voltage holding unit has an inductor, the first transistor has an oxide semiconductor in a channel formation region; the second transistor has a nitride semiconductor in a channel formation region, the third transistor has silicon in a channel formation region; the inductor is provided in a layer above a layer in which the second transistor and the third transistor are provided; the first transistor is provided in a layer above the layer in which the inductor is provided; Semiconductor device.

3. In claim 1 or claim 2, The semiconductor device, wherein the oxide semiconductor contains In, Ga, and Zn.

4. In any one of claims 1 to 3, The nitride semiconductor device includes Ga.

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