Logic circuit and semiconductor device using unipolar transistor

Abstract

A semiconductor device using a unipolar transistor is provided, in which a steady-state current does not flow and a high level or a low level can be represented with a high power supply potential and a low power supply potential. The semiconductor device includes first to fourth transistors, first and second capacitor elements, first and second wirings, first and second input terminals, and an output terminal. One of a source and a drain of the fourth transistor is electrically connected to the first wiring, and the other of the source and the drain of the fourth transistor is electrically connected to one of a source and a drain of the second transistor, one terminal of the second capacitor element, and a gate of the third transistor. A gate of the fourth transistor is electrically connected to the first input terminal, one terminal of the first capacitor element, and a gate of the first transistor, and a gate of the second transistor is electrically connected to the second input terminal. One of a source and a drain of the first transistor is electrically connected to the first wiring, and the other of the source and the drain of the first transistor is electrically connected to the other terminal of the first capacitor element, the other terminal of the second capacitor element, one of a source and a drain of the third transistor, and the output terminal. The other of the source and the drain of the second transistor and the other of the source and the drain of the third transistor are electrically connected to the second wiring.

Description

TECHNICAL FIELD

[0001] One embodiment of the present application is a logic circuit configured using a unipolar transistor.

[0002] In addition, one embodiment of the present application relates to a semiconductor device. Note that a semiconductor device in this specification and the like means a device that can function by utilizing semiconductor characteristics. For example, an integrated circuit, a chip including an integrated circuit, an electronic component provided with the chip, and an electronic device provided with the integrated circuit are all examples of the semiconductor device.

[0003] Note that one embodiment of the present application is not limited to the technical field described above. The technical field of the invention disclosed in this specification and the like is an object, a method, or a manufacturing method. In addition, one embodiment of the present application relates to a process, a machine, an article of manufacture, or a composition of matter. BACKGROUND

[0004] As a circuit that processes a digital signal represented by a high level or a low level (sometimes represented by High or Low, H or L, 1 or 0, or the like) (also referred to as a digital circuit or a logic circuit), a CMOS (Complementary Metal Oxide Semiconductor) circuit is widely used.

[0005] In many cases, a logic circuit is supplied with a high power supply potential and a low power supply potential, and a high level is represented by the high power supply potential and a low level is represented by the low power supply potential. In addition, a CMOS circuit is configured using, for example, an n-channel transistor and a p-channel transistor formed over a single-crystal silicon substrate.

[0006] A CMOS circuit has a circuit structure in which an n-channel transistor and a p-channel transistor are connected in series between a high power supply potential and a low power supply potential, and the p-channel transistor is in a non-conductive state in the case where the n-channel transistor is in a conductive state and the n-channel transistor is in a non-conductive state in the case where the p-channel transistor is in a conductive state. In other words, it has a characteristic in which current does not flow from the high power supply potential to the low power supply potential (except for off-state current of a transistor or the like) after a high level or a low level is determined.

[0007] Here, in the case where an n-channel transistor and a p-channel transistor cannot be manufactured or in the case where a manufacturing process of a transistor is reduced in order to reduce cost or the like, a logic circuit is sometimes configured using only one of an n-channel transistor and a p-channel transistor (also referred to as a unipolar transistor or a single-channel transistor).

[0008] For example, Patent Document 1 and Patent Document 2 disclose examples of a semiconductor device or a driving circuit of a display device configured using unipolar transistors. In Patent Document 1 and Patent Document 2, the circuit has a structure in which two unipolar transistors are connected in series between a high power supply potential and a low power supply potential, a first signal and a second signal obtained by inverting the logic (high level or low level) of the first signal are each input to the gate of the transistor, and a through current does not flow from the high power supply potential to the low power supply potential. The method of using the first signal and the second signal obtained by inverting the logic of the first signal is sometimes referred to as dual rail.

[0009] In addition, in Patent Document 1 and Patent Document 2, a capacitor is provided between the output terminal and the gate of one transistor, so that a problem in which one of the high level and the low level of the output signal does not reach the high power supply potential or the low power supply potential is solved. The method of providing the capacitor between the output terminal and the gate of one transistor is sometimes referred to as bootstrap.

[0010] On the other hand, in recent years, a transistor including a metal oxide in a channel formation region (also referred to as an oxide semiconductor transistor or an OS transistor) has attracted attention. As the OS transistor, an n-channel transistor has been put into practical use, which has characteristics such as a very small off-state current, a high voltage applied between a source and a drain (that is, high withstand voltage), and a stacked structure. Further, the OS transistor has characteristics such as a small increase in off-state current in a high-temperature environment and a large ratio of on-state current to off-state current in a high-temperature environment. A semiconductor device including the OS transistor has high reliability.

[0011] For example, Patent Document 3 discloses a semiconductor device including a plurality of memory cells using OS transistors over a semiconductor substrate on which a peripheral circuit such as a driving circuit or a control circuit is formed, and an example in which the OS transistor is used in a memory cell of a DRAM (Dynamic Random Access Memory). For example, a Si transistor formed over a single crystal silicon substrate can be used for the peripheral circuit, and the memory cell using the OS transistor can be provided thereover. When the memory cell using the OS transistor is provided over the single crystal silicon substrate on which the peripheral circuit is formed, a chip area can be reduced. Further, since the off-state current of the OS transistor is very small, data can be held for a long time.

[0012] [Patent Document]

[0013] [Non-Patent Document]

[0014] [Patent Document 1] Japanese Published Patent Application No. H9-246936

[0015] [Patent Document 2] Japanese Published Patent Application No. 2002-328643

[0016] [Patent Document 3] Japanese Published Patent Application No. 2012-256820 SUMMARY

[0017] PROBLEMS TO BE SOLVED BY THE INVENTION

[0018] Patent Document 1 and Patent Document 2 disclose a circuit that is a logic circuit configured using a unipolar transistor with double tracks and bootstrap, has a feature that current does not flow from a high power supply potential to a low power supply potential (it can also be said that steady-state current does not flow) after it is determined whether a high level or a low level, and can use the high power supply potential and the low power supply potential to represent the high level and the low level, respectively.

[0019] Here, in bootstrap, it is preferable to secure a voltage Vgs of a gate with respect to a source of a transistor in a transistor in which a capacitor is provided between the source and the gate. If the voltage Vgs of the gate with respect to the source of the transistor is not sufficiently secured, sometimes the high level does not rise to the high power supply potential or the low level does not fall to the low power supply potential.

[0020] In Patent Document 1 and Patent Document 2, the source of the transistor is electrically connected to an output terminal, and the capacitor is provided between the source and the gate of the transistor. For example, in the case where a capacitive load is connected to the output terminal, in the case where it is the high level, sometimes the potential of the output terminal does not rise to the high power supply potential or in the case where it is the low level, sometimes the potential of the output terminal does not fall to the low power supply potential.

[0021] One of objects of one embodiment of the present application is to provide a logic circuit configured using a unipolar transistor with no steady-state current flowing, in which a potential of an output terminal rises to a high power supply potential when an output is a high level and falls to a low power supply potential when the output is a low level. Another object of one embodiment of the present application is to provide a semiconductor device configured using a unipolar transistor with no steady-state current flowing, in which a potential of an output terminal rises to a high power supply potential when an output is a high level and falls to a low power supply potential when the output is a low level.

[0022] Note that one embodiment of the present application does not necessarily achieve all the above objects, and at least one of the objects is sufficient. Furthermore, the inclusion of the above objects does not preclude the existence of other objects. Objects other than the above can be apparent from the description, claims, drawings, and the like, and can be extracted from the description, claims, drawings, and the like.

[0023] MEANS OF SOLVING THE PROBLEMS

[0024] One embodiment of the present application is a semiconductor device including first to fourth transistors, first and second capacitor elements, first and second wiring lines, first and second input terminals, and an output terminal. One of a source and a drain of the fourth transistor is electrically connected to the first wiring line, the other of the source and the drain of the fourth transistor is electrically connected to one of a source and a drain of the second transistor, one terminal of the second capacitor element, and a gate of the third transistor, and the other of the source and the drain of the second transistor is electrically connected to the second wiring line. A gate of the fourth transistor is electrically connected to the first input terminal, one terminal of the first capacitor element, and a gate of the first transistor, and a gate of the second transistor is electrically connected to the second input terminal. One of a source and a drain of the first transistor is electrically connected to the first wiring line, the other of the source and the drain of the first transistor is electrically connected to the other terminal of the first capacitor element, the other terminal of the second capacitor element, one of a source and a drain of the third transistor, and the output terminal, and the other of the source and the drain of the third transistor is electrically connected to the second wiring line.

[0025] In the above embodiment, the first wiring line is supplied with a first potential, the second wiring line is supplied with a second potential, the second potential is higher than the first potential, a first signal is input to the first input terminal, and a second signal is input to the second input terminal, the second signal being a logically inverted signal of the first signal.

[0026] In the above embodiment, the first to fourth transistors are n-channel transistors.

[0027] In the above embodiment, the first to fourth transistors include a metal oxide in a channel formation region.

[0028] One embodiment of the present application is a semiconductor device including first to third transistors, first and second capacitor elements, first and second wiring lines, first and second input terminals, and an output terminal. One of a source and a drain of the second transistor is electrically connected to the second input terminal, the other of the source and the drain of the second transistor is electrically connected to one terminal of the second capacitor element and a gate of the third transistor, and a gate of the second transistor is electrically connected to the second wiring line. One of a source and a drain of the first transistor is electrically connected to the first wiring line, a gate of the first transistor is electrically connected to the first input terminal and one terminal of the first capacitor element, and the other of the source and the drain of the first transistor is electrically connected to the other terminal of the first capacitor element, the other terminal of the second capacitor element, one of a source and a drain of the third transistor, and the output terminal. The other of the source and the drain of the third transistor is electrically connected to the second wiring line.

[0029] In the above-described aspect, the first wiring is supplied with a first potential, the second wiring is supplied with a second potential that is higher than the first potential, the first signal is input to the first input terminal, and the second signal is input to the second input terminal.

[0030] In the above-described aspect, the first to third transistors are n-channel transistors.

[0031] In the above-described aspect, the first to third transistors include a metal oxide in a channel formation region.

[0032] In one embodiment of the present application, a semiconductor device includes a first to a seventh transistor, a first to a third capacitor element, a first and a second wiring, a first to a fourth input terminal, and an output terminal. One of a source and a drain of the sixth transistor is electrically connected to the first wiring, the other of the source and the drain of the sixth transistor is electrically connected to one of a source and a drain of the seventh transistor, the other of the source and the drain of the seventh transistor is electrically connected to one of the source and the drain of the third transistor, one of the source and the drain of the fourth transistor, one terminal of the third capacitor element, and a gate of the fifth transistor, the other of the source and the drain of the third transistor and the other of the source and the drain of the fourth transistor are electrically connected to the second wiring. A gate of the sixth transistor is electrically connected to the second input terminal, one terminal of the second capacitor element, and a gate of the first transistor, a gate of the seventh transistor is electrically connected to the first input terminal, one terminal of the first capacitor element, and a gate of the second transistor, a gate of the third transistor is electrically connected to the third input terminal, and a gate of the fourth transistor is electrically connected to the fourth input terminal. One of the source and the drain of the first transistor is electrically connected to the first wiring, the other of the source and the drain of the first transistor is electrically connected to one of the source and the drain of the second transistor, the other of the source and the drain of the second transistor is electrically connected to the other terminal of the first capacitor element, the other terminal of the second capacitor element, the other terminal of the third capacitor element, one of the source and the drain of the fifth transistor, and the output terminal, and the other of the source and the drain of the fifth transistor is electrically connected to the second wiring.

[0033] In the above-described aspect, the first wiring is supplied with a first potential, the second wiring is supplied with a second potential that is higher than the first potential, the first signal is input to the first input terminal, the second signal is input to the second input terminal, the third signal is input to the third input terminal, the fourth signal is input to the fourth input terminal, the third signal is a signal that is a logical inversion of the first signal, and the fourth signal is a signal that is a logical inversion of the second signal.

[0034] In the above-described aspect, the first to seventh transistors are n-channel transistors.

[0035] In the above-described manner, the first to seventh transistors include a metal oxide in a channel formation region.

[0036] In the above-described manner, one of a source and a drain of the sixth transistor and one of a source and a drain of the seventh transistor are electrically connected to the first wiring, the other of the source and the drain of the sixth transistor is electrically connected to the other of the source and the drain of the seventh transistor, one of a source and a drain of the third transistor, one terminal of the third capacitor, and a gate of the fifth transistor, the other of the source and the drain of the third transistor is electrically connected to one of a source and a drain of the fourth transistor, and the other of the source and the drain of the fourth transistor is electrically connected to the second wiring. A gate of the sixth transistor is electrically connected to the first input terminal, one terminal of the first capacitor, and a gate of the first transistor, a gate of the seventh transistor is electrically connected to the second input terminal, one terminal of the second capacitor, and a gate of the second transistor, a gate of the third transistor is electrically connected to the third input terminal, and a gate of the fourth transistor is electrically connected to the fourth input terminal. One of a source and a drain of the first transistor and one of a source and a drain of the second transistor are electrically connected to the first wiring, the other of the source and the drain of the first transistor is electrically connected to the other of the source and the drain of the second transistor, the other terminal of the first capacitor, the other terminal of the second capacitor, the other terminal of the third capacitor, one of a source and a drain of the fifth transistor, and the output terminal, the other of the source and the drain of the fifth transistor is electrically connected to the second wiring.

[0037] In the above-described manner, the first wiring is supplied with a first potential, the second wiring is supplied with a second potential, the second potential is a higher potential than the first potential, a first signal is input to the first input terminal, a second signal is input to the second input terminal, a third signal is input to the third input terminal, a fourth signal is input to the fourth input terminal, the third signal is a logically inverted signal of the first signal, and the fourth signal is a logically inverted signal of the second signal.

[0038] In the above-described manner, the first to seventh transistors are n-channel transistors.

[0039] In the above-described manner, the first to seventh transistors include a metal oxide in a channel formation region.

[0040] Effects of Invention

[0041] According to one embodiment of the present application, a logic circuit can be provided which is configured using unipolar transistors and in which no steady-state current flows, the potential of an output terminal rises to a high power supply potential when the output is high, and the potential of the output terminal falls to a low power supply potential when the output is low. According to one embodiment of the present application, a semiconductor device can be provided which is configured using unipolar transistors and in which no steady-state current flows, the potential of an output terminal rises to a high power supply potential when the output is high, and the potential of the output terminal falls to a low power supply potential when the output is low.

[0042] Note that the description of these effects does not preclude the presence of other effects. Furthermore, one embodiment of the present application does not need to achieve all of the effects described above. Other effects in addition to those described above will be apparent to those skilled in the art, from the description of the specification, the attached claims, drawings, and the like. Still other effects will be apparent to those skilled in the art, from the description of the specification, the attached claims, drawings, and the like.

[0043] BRIEF DESCRIPTION OF DRAWINGS

[0044] FIG. 1A FIG. 1B FIG. 1 is a circuit diagram illustrating a structure example of a semiconductor device.

[0045] FIG. 2 FIG. 2 is a timing chart.

[0046] FIG. 3 FIG. 3 is a timing chart.

[0047] FIG. 4A FIG. 4B FIG. 4 is a diagram illustrating a circuit symbol of a transistor. FIG. 4C FIG. 4D FIG. 5 is a circuit diagram illustrating a structure example of a semiconductor device.

[0048] FIG. 5 FIG. 6 is a circuit diagram illustrating a structure example of a semiconductor device.

[0049] FIG. 6 FIG. 7 is a timing chart.

[0050] FIG. 7A FIG. 7B FIG. 8 is a circuit diagram illustrating a structure example of a semiconductor device.

[0051] FIG. 8 FIG. 9 is a timing chart.

[0052] FIG. 9A FIG. 9B FIG. 10 is a diagram illustrating a symbol of a semiconductor device.

[0053] FIG. 10A FIG. 10B FIG. 11 is a block diagram illustrating a structure example of a semiconductor device. ​​​​​​

[0054] FIG. 11 is a timing chart.

[0055] FIG. 12 is a timing chart.

[0056] FIG. 13 is a cross-sectional view showing a structure example of a semiconductor device.

[0057] FIG. 14A FIG. 14B FIG. 14C is a cross-sectional view showing a structure example of a transistor.

[0058] FIG. 15A is a top view showing a structure example of a transistor. FIG. 15B FIG. 15C is a cross-sectional view showing a structure example of a transistor.

[0059] FIG. 16A is a top view showing a structure example of a transistor. FIG. 16B FIG. 16C is a cross-sectional view showing a structure example of a transistor.

[0060] FIG. 17A is a top view showing a structure example of a transistor. FIG. 17B FIG. 17C is a cross-sectional view showing a structure example of a transistor.

[0061] FIG. 18A is a top view showing a structure example of a transistor. FIG. 18B FIG. 18C is a cross-sectional view showing a structure example of a transistor.

[0062] FIG. 19A is a top view showing a structure example of a transistor. FIG. 19B FIG. 19C is a cross-sectional view showing a structure example of a transistor.

[0063] FIG. 20A is a top view showing a structure example of a transistor. FIG. 20B FIG. 20C is a cross-sectional view showing a structure example of a transistor.

[0064] FIG. 21A FIG. 21B is a cross-sectional view showing a structure example of a transistor.

[0065] FIG. 22 is a cross-sectional view showing a structure example of a semiconductor device.

[0066] FIG. 23A FIG. 23B is a cross-sectional view showing a structure example of a transistor.​​​​​​​​​​

[0067] Means for carrying out the present application

[0068] Embodiments will be described below with reference to the accompanying drawings. Note that one embodiment of the present application can be implemented in many different modes, and it is easily understood by those skilled in the art that the modes and details thereof can be changed in various ways unless otherwise specified, without departing from the spirit and scope of the present application. Therefore, the present application should not be interpreted as being limited to the content described in the following embodiments.

[0069] The embodiments described below can be appropriately combined. In addition, when a plurality of structural examples is shown in one embodiment, the structural examples can be appropriately combined with each other.

[0070] The block diagram of this specification shows constituent elements classified in independent blocks according to their functions, but actual constituent elements are hardly clearly divided according to functions, and one constituent element sometimes has a plurality of functions.

[0071] In the drawings and the like, the size, the thickness of layers, regions, and the like are sometimes exaggerated for the sake of convenience. Therefore, the present application is not limited to the dimensions shown in the drawings. In the drawings, schematic examples are shown, and therefore the present application is not limited to the shapes, values, and the like shown in the drawings.

[0072] In the drawings and the like, the same reference numerals are used for the same constituent elements, constituent elements having the same function, constituent elements formed of the same material, or constituent elements formed at the same time, and the like, and repetitive explanation is sometimes omitted.

[0073] In this specification and the like, "film" and "layer" can be interchanged with each other. For example, "conductive layer" can be interchanged with "conductive film". Furthermore, "insulating film" can be interchanged with "insulating layer".

[0074] In this specification and the like, the words "over" and "under" and the like are used to express the positional relationship of one constituent element with another when the one constituent element is above or below the other constituent element with reference to the drawings. Specifically, the positional relationship varies with the drawings. Thus, the positional relationship of one constituent element with another is not necessarily the one shown in the drawings, and can be opposite to the one shown in the drawings.

[0075] In addition, ordinal numbers such as "first", "second", and "third" in this specification and the like are added to avoid confusion among constituent elements and do not limit the number thereof in any other way.

[0076] In this specification and the like, "electrically connected" includes the case where "an element having some function" is connected. Here, "an element having some function" is not particularly limited as long as it can transmit and receive an electrical signal between objects to be connected. For example, "an element having some function" includes not only an electrode and a wiring but also a switching element such as a transistor, a resistor, an inductor, a capacitor, another element having various functions, and the like. Thus, even when it is stated that "electrically connected", there is a case where only a wiring is extended without a physical connection in an actual circuit.

[0077] In this specification and the like, "an electrode" or "a wiring" is not limited to a function of a constituent element. For example, "an electrode" is used as a part of "a wiring" in some cases, and vice versa.

[0078] In this specification and the like, a "terminal" in an electronic circuit means a portion which performs input (or output) of current or potential or reception (or transmission) of a signal. Thus, a part of a wiring or an electrode is used as a terminal in some cases.

[0079] In general, a "capacitor" has a structure in which two electrodes face each other with an insulator (dielectric) interposed therebetween. In this specification and the like, a case where "a capacitor element" is the above "capacitor" is included. In other words, a case where "a capacitor element" has a structure in which two electrodes face each other with an insulator interposed therebetween, a case where "a capacitor element" has a structure in which two wirings face each other with an insulator interposed therebetween, or a case where "a capacitor element" has a structure in which two wirings are arranged with an insulator interposed therebetween is included.

[0080] Note that in this specification and the like, "a voltage" refers to a potential difference between a certain potential and a reference potential (e.g., a ground potential) in many cases. Thus, a voltage and a potential difference can be exchanged with each other.

[0081] In this specification and the like, a transistor refers to an element including at least three terminals of a gate, a drain, and a source. A transistor has a channel formation region between the drain and the source, and current can flow through the channel formation region from the drain to the source. Note that in this specification and the like, the channel formation region refers to a region where a current mainly flows.

[0082] In addition, the functions of the source and the drain are sometimes interchangeable with each other in this specification and the like. Therefore, the source and the drain can be interchanged with each other in this specification and the like.

[0083] In addition, in this specification and the like, a drain current refers to a drain current when a transistor is in an off state (also referred to as a non-conduction state, a blocking state) unless specifically stated otherwise. In the n-channel transistor, the off state refers to a state where a voltage Vgs between a gate and a source is lower than a threshold voltage Vth unless specifically stated otherwise, and in the p-channel transistor, the off state refers to a state where the voltage Vgs between the gate and the source is higher than the threshold voltage Vth. That is, the off-state current of the n-channel transistor refers to a drain current when the voltage Vgs between the gate and the source is lower than the threshold voltage Vth.

[0084] In the above description of the off-state current, the drain can be referred to as the source. That is, the off-state current refers to a source current when a transistor is in an off state. In addition, a leakage current refers to the same meaning as the off-state current. In this specification and the like, the off-state current refers to a current flowing between a source and a drain when the transistor is in an off state.

[0085] In this specification and the like, an on-state current refers to a current flowing between a source and a drain when a transistor is in an on state (also referred to as a conduction state).

[0086] In this specification and the like, a metal oxide refers to an oxide of a metal in a broad sense. Metal oxides are classified into an oxide insulator, an oxide conductor (including a transparent oxide conductor), an oxide semiconductor, and the like.

[0087] For example, in the case where a metal oxide is used for a channel formation region of a transistor, the metal oxide is sometimes referred to as an oxide semiconductor. In other words, in the case where a metal oxide has at least one of amplifying function, rectifying function, and switching function, the metal oxide can be referred to as a metal oxide semiconductor. That is, a transistor including a metal oxide in a channel formation region can be referred to as an "oxide semiconductor transistor" or an "OS transistor". Similarly, the above-described "transistor using an oxide semiconductor" is a transistor including a metal oxide in a channel formation region.

[0088] Further, in this specification and the like, a metal oxide including nitrogen is also referred to as a metal oxide (metal oxide) in some cases. Further, a metal oxide including nitrogen can be referred to as a metal oxynitride (metal oxynitride). Details of a metal oxide will be described later.

[0089] (Embodiment 1)

[0090] In this embodiment, a structure example of a semiconductor device according to one embodiment of the present application will be described. The semiconductor device according to one embodiment of the present application is a logic circuit configured using unipolar transistors, and uses a high power supply potential to represent a high level and a low power supply potential to represent a low level.

[0091] Note that an example in which an n-channel transistor is used in the semiconductor device described in this specification and the like is shown, but a p-channel transistor can be used. A person with ordinary skill in the art can easily understand that the n-channel transistor is changed to a p-channel transistor, and thus the description thereof is omitted.

[0092] <Structure Example 1 of Semiconductor Device>

[0093] FIG. 1A is a circuit diagram showing a structure example of a semiconductor device 10. The semiconductor device 10 is a semiconductor device according to one embodiment of the present application, and includes transistors 11 to 14, a capacitor element Cll, and a capacitor element C12. The transistors 11 to 14 are n-channel transistors.

[0094] The semiconductor device 10 includes a wiring VSS_IN to which a low power supply potential VSS is supplied, a wiring VDD_IN to which a high power supply potential VDD is supplied, an input terminal SI_IN to which a signal SI is input, an input terminal SIB_IN to which a signal SIB is input, and an output terminal SO_OUT from which a signal SO is output.

[0095] Here, the high power supply potential VDD is a potential higher than the low power supply potential VSS, and the low power supply potential VSS can be a standard potential in the semiconductor device 10. In addition, the signals SI and SIB are digital signals, and the potential representing a high level of the signals SI and SIB is the high power supply potential VDD, and the potential representing a low level is the low power supply potential VSS. In addition, the signal SIB is a signal obtained by logically inverting the signal SI.

[0096] In the semiconductor device 10, one of the source and the drain of the transistor 14 is electrically connected to the wiring VSS_IN, the other of the source and the drain of the transistor 14 is electrically connected to one of the source and the drain of the transistor 12, one terminal of the capacitor element C12, and the gate of the transistor 13, and the other of the source and the drain of the transistor 12 is electrically connected to the wiring VDD_IN.

[0097] The gate of the transistor 14 is electrically connected to the input terminal SI_IN, one terminal of the capacitor element Cll, and the gate of the transistor 11, and the gate of the transistor 12 is electrically connected to the input terminal SIB_IN.

[0098] One of the source and drain of the transistor 11 is electrically connected to the wiring VSS_IN, and the other of the source and drain of the transistor 11 is electrically connected to the other terminal of the capacitive element C11, the other terminal of the capacitive element C12, one of the source and drain of the transistor 13, and the output terminal SO_OUT, and the other of the source and drain of the transistor 13 is electrically connected to the wiring VDD_IN.

[0099] Here, the connection portion of the other of the source and drain of the transistor 14, one of the source and drain of the transistor 12, one terminal of the capacitive element C12, and the gate of the transistor 13 is referred to as a node N11.

[0100] <Structure Example 2 of Semiconductor Device>

[0101] FIG. 1B is a circuit diagram illustrating a structure example of a semiconductor device 20. The semiconductor device 20 is a semiconductor device according to one embodiment of the present application, and is a structure example different from the semiconductor device 10. The semiconductor device 20 includes transistors 21 to 23, a capacitive element C21, and a capacitive element C22. The transistors 21 to 23 are n-channel transistors.

[0102] The semiconductor device 20 includes the wiring VSS_IN to which the low power supply potential VSS is supplied, the wiring VDD_IN to which the high power supply potential VDD is supplied, the input terminal SI_IN to which the signal SI is input, the input terminal SIB_IN to which the signal SIB is input, and the output terminal SO_OUT from which the signal SO is output, like the semiconductor device 10. Note that the description of the potentials and the signals is omitted in order to avoid repetition.

[0103] In the semiconductor device 20, one of the source and drain of the transistor 22 is electrically connected to the input terminal SIB_IN, the other of the source and drain of the transistor 22 is electrically connected to one terminal of the capacitive element C22 and the gate of the transistor 23, and the gate of the transistor 22 is electrically connected to the wiring VDD_IN.

[0104] One of the source and drain of the transistor 21 is electrically connected to the wiring VSS_IN, the gate of the transistor 21 is electrically connected to the input terminal SI_IN and one terminal of the capacitive element C21, the other of the source and drain of the transistor 21 is electrically connected to the other terminal of the capacitive element C21, the other terminal of the capacitive element C22, one of the source and drain of the transistor 23, and the output terminal SO_OUT, and the other of the source and drain of the transistor 23 is electrically connected to the wiring VDD_IN.

[0105] Here, the connection portion of the other of the source and drain of the transistor 22, one terminal of the capacitive element C22, and the gate of the transistor 23 is referred to as a node N21.

[0106] <Operation example 1 of semiconductor device>

[0107] FIG. 2 is a timing chart showing an operation example of the semiconductor device 10. In FIG. 2 , the potential of the signal SI, the signal SIB, the node N11, and the signal SO is shown divided into the period D11 to the period D15. Note that the threshold voltage of the transistors 11 to 14 is set to the threshold voltage Vth.

[0108] The period D11 is a period in which the signal SI is at a high level and the signal SIB is at a low level. Since the signal SI is at the high level, the transistors 11 and 14 are in an on state, and the node N11 and the signal SO are at a low level. In addition, the transistors 12 and 13 are in an off state.

[0109] The period D12 is a part of a period in which the signal SI changes from the high level to the low level and the signal SIB changes from the low level to the high level (the period in which the signal changes from the high level to the low level is also referred to as a falling period, and the period in which the signal changes from the low level to the high level is also referred to as a rising period).

[0110] In the period D12, due to the capacitive coupling through the capacitive element C11, as the signal SI changes from the high level to the low level, the potential of the signal SO becomes a potential lower than the low level (the low power supply potential VSS). In addition, the signal SIB rises from the low level, and in a case where the potential difference between the signal SIB and the node N11 exceeds the threshold voltage Vth of the transistor 12, the transistor 12 becomes in the on state, and the potential of the node N11 rises from the low level. When the potential of the node N11 rises from the low level, the transistor 13 also becomes in the on state, and thus the degree to which the potential of the signal SO falls from the low level is reduced, and in the period D13 described later, the potential of the signal SO starts to rise.

[0111] The period D13 is a part of the falling period of the signal SI and a period of the low level, and is a part of the rising period of the signal SIB and a period of the high level. In the period D13, the transistors 12 and 13 are in the on state, the potential of the node N11 rises, and the potential of the signal SO, which is at a potential lower than the low level, also starts to rise. In addition, the transistors 11 and 14 become in the off state.

[0112] During D13, although the potential of the node N11 and the signal SO rises, the signal SO rises from a potential lower than the low level, and thus a potential difference between the node N11 and the signal SO is generated. In addition, the signal SIB becomes the high level and the potential of the node N11 rises, and the potential difference between the signal SIB and the node N11 is smaller than the threshold voltage Vth of the transistor 12, at which time the transistor 12 becomes the non-conducting state. Although the transistor 12 becomes the non-conducting state, the potential of the node N11 further rises as the potential of the signal SO rises due to the capacitive coupling through the capacitive element C12. In other words, because of the potential difference between the node N11 and the signal SO, the potential of the node N11 can be surely raised.

[0113] The potential of the node N11 rises beyond the high power supply potential VDD, and thus the transistor 13 does not become the non-conducting state even if the potential difference between the signal SO and the high power supply potential VDD becomes smaller than the threshold voltage Vth of the transistor 13. The signal SO rises until it has a potential equal to the high power supply potential VDD.

[0114] During D14 is a period during which the signal SI rises and the signal SIB falls. During D14, the transistor 11 and the transistor 14 become the conducting state, and the transistor 12 and the transistor 13 become the non-conducting state. In other words, the node N11 and the signal SO become the low level.

[0115] During D15 is a period during which the signal SI is at the high level and the signal SIB is at the low level. During D15 is the same as during D11, and thus the description is omitted.

[0116] As described above, the semiconductor device 10 is a logic circuit configured using n-channel transistors, and the signal SO output from the output terminal SO_OUT rises to the high power supply potential VDD when it is at the high level and falls to the low power supply potential VSS when it is at the low level. In addition, the semiconductor device 10 has the following feature: after it is determined whether the signal SI and the signal SIB are at the high level or the low level, a through current does not flow from the high power supply potential VDD to the low power supply potential VSS.

[0117] <Operation Example 2 of Semiconductor Device>

[0118] FIG. 3 is a timing chart showing an operation example of the semiconductor device 20. In FIG. 3 , the potential of the signal SI, the signal SIB, the node N21, and the signal SO is shown divided into during D21 to during D25. Note that the threshold voltage of the transistor 21 to the transistor 23 is set to the threshold voltage Vth.

[0119] Period D21 is a period during which the signal SI is at a high level and the signal SIB is at a low level. Since the signal SI is at a high level, the transistor 21 is in an on state, and the signal SO is at a low level. In addition, the transistor 22 is in an on state, and the potential of the node N21 is at a low level as with the signal SIB. Therefore, the transistor 23 is in an off state.

[0120] Period D22 is a part of a period during which the signal SI changes from a high level to a low level and the signal SIB changes from a low level to a high level.

[0121] In period D22, the potential of the signal SO changes to a potential lower than a low level due to capacitive coupling through the capacitive element C21 as the signal SI changes from a high level to a low level. In addition, the signal SIB rises from a low level, and the potential of the node N21 rises as with the signal SIB. When the potential of the node N21 rises from a low level, the transistor 23 changes to an on state, and thus the potential of the signal SO decreases from a low level to a lower extent, and the potential of the signal SO starts to rise in period D23 described later.

[0122] Period D23 is a part of a period during which the signal SI falls and a period during which it is at a low level, and is a part of a period during which the signal SIB rises and a period during which it is at a high level. In period D23, the potential of the node N21 further rises, the transistor 23 is in an on state, and the potential of the signal SO which is at a potential lower than a low level also starts to rise. In addition, the transistor 21 changes to an off state.

[0123] In period D23, although the potentials of the node N21 and the signal SO rise, the signal SO rises from a potential lower than a low level, and thus a potential difference between the node N21 and the signal SO is generated. In addition, the signal SIB changes to a high level and the potential of the node N21 rises, and the potential difference between the node N21 and the high power supply potential VDD is smaller than the threshold voltage Vth of the transistor 22, and at this time the transistor 22 changes to an off state. Although the transistor 22 changes to an off state, the potential of the node N21 further rises due to capacitive coupling through the capacitive element C22 as the potential of the signal SO rises. In other words, since there is a potential difference between the node N21 and the signal SO, the potential of the node N21 can be surely raised.

[0124] The potential of the node N21 rises beyond the high power supply potential VDD, and thus the transistor 23 does not change to an off state even if the potential difference between the signal SO and the high power supply potential VDD becomes smaller than the threshold voltage Vth of the transistor 23. The signal SO rises until it has a potential equal to the high power supply potential VDD.

[0125] Period D24 is a period in which the signal SI rises and the signal SIB falls. In the period D24, the transistor 21 becomes an on state, the potential of the node N21 falls, and the transistor 23 becomes an off state. In other words, the node N21 and the signal SO become a low level.

[0126] Period D25 is a period in which the signal SI is at a high level and the signal SIB is at a low level. The period D25 is the same as the period D21, and thus the description is omitted.

[0127] As described above, the semiconductor device 20 is a logic circuit configured using n-channel transistors, and the signal SO output from the output terminal SO_OUT rises to the high power supply potential VDD when at a high level and falls to the low power supply potential VSS when at a low level. In addition, the semiconductor device 20 has a feature in which a through current does not flow from the high power supply potential VDD to the low power supply potential VSS after it is determined whether the signal SI and the signal SIB are at a high level or a low level.

[0128] <Transistors Configuring Semiconductor Devices>

[0129] As the transistors 11 to 14 configuring the semiconductor device 10 and the transistors 21 to 23 configuring the semiconductor device 20, transistors (OS transistors) including a metal oxide in a channel formation region can be used.

[0130] The OS transistor has a feature in which an off-state current is very small, a high voltage can be applied between a source and a drain, can be stacked due to being a thin film transistor, and the like. Here, the off-state current refers to a drain current when a transistor is in an off state, and since the band gap of an oxide semiconductor is 2.5 eV or more, preferably 3.0 eV or more, the OS transistor has a feature in which a leakage current due to thermal excitation is small and the off-state current is also very small. In the OS transistor, for example, the off-state current per channel width of 1 μm can be 100 zA / μm or less, 10 zA / μm or less, 1 zA / μm or less, or 10 yA / μm or less.

[0131] In particular, as the transistors 12, 14, and 22, a transistor with a small off-state current is preferably used. Thus, in the period D13 or the period D23, even if the period in which the signal SI is at a low level (the period in which the signal SIB is at a high level) is long, the potential of the node N11 or the node N21 which rises above the high power supply potential VDD can be maintained for a long time.

[0132] In addition, the OS transistor has a feature in which the off-state current does not easily increase in a high-temperature environment, and the ratio of an on-state current to the off-state current is large in a high-temperature environment. By using the OS transistor to configure the semiconductor device 10 or the semiconductor device 20, the reliability of the semiconductor device can be improved.

[0133] The metal oxide used for the channel formation region of the OS transistor is preferably an oxide semiconductor including at least one of indium (In) and zinc (Zn). A typical example of such an oxide semiconductor is an In-M-Zn oxide (where M is an element such as Al, Ga, Y, or Sn). The oxide semiconductor can be made i-type (intrinsic) or substantially i-type by reducing impurities such as water or hydrogen serving as an electron donor (donor) and reducing oxygen vacancies. The oxide semiconductor can be referred to as a high-purity oxide semiconductor. Note that details of the OS transistor are described in Embodiment 3 and Embodiment 4.

[0134] In addition, since the OS transistor is a thin film transistor, the transistor can be provided in a stacked manner. For example, the OS transistor can be provided over a circuit including an Si transistor formed over a single crystal silicon substrate, or the like. Thus, the chip area of the semiconductor device 10 or the semiconductor device 20 can be reduced.

[0135] Alternatively, a transistor other than the OS transistor can be used as the transistors 11 to 14 included in the semiconductor device 10 and the transistors 21 to 23 included in the semiconductor device 20. For example, a transistor including a semiconductor having a large band gap in a channel formation region can be used. The semiconductor having a large band gap is sometimes referred to as a semiconductor having a band gap of 2.2 eV or more, and examples thereof include silicon carbide, gallium nitride, diamond, and the like.

[0136] In addition, a transistor including a back gate can be used as the transistors 11 to 14 included in the semiconductor device 10 and the transistors 21 to 23 included in the semiconductor device 20.

[0137] As an example of the transistor including a back gate, FIG. 4A A circuit symbol of the transistor 31 is shown. The transistor 31 includes four terminals which are referred to as a gate (also referred to as a front gate), a drain, a source, and a back gate. In FIG. 4A In the drawing, the four terminals are denoted as G (gate), D (drain), S (source), and BG (back gate), respectively.

[0138] As an example of use of the transistor 31, the back gate can be electrically connected to the gate, the back gate can be electrically connected to the source, a predetermined potential can be supplied to the back gate, or the back gate can be in an electrically floating state (also referred to as floating). For example, by electrically connecting the back gate to the gate, the on-state current of the transistor 31 can be increased. In addition, by supplying a predetermined potential to the back gate, the threshold voltage of the transistor 31 can be changed. An example of a cross-sectional structure of a transistor including a back gate will be described in Embodiment 3.

[0139] Further, as the transistors 11 to 14 configuring the semiconductor device 10 and the transistors 21 to 23 configuring the semiconductor device 20, a transistor including a plurality of gates (also referred to as a multigate) can be used.

[0140] As an example of the transistor including a plurality of gates, FIG. 4B A circuit diagram symbol of a transistor 32 including two gates (also referred to as a dual gate) is shown. The transistor 32 includes four terminals (gate 1, gate 2, drain, and source). In FIG. 4B In the present embodiment, the four terminals are denoted as G1 (gate 1), G2 (gate 2), D (drain), and S (source), respectively.

[0141] As an example of use of the transistor 32, the gate 1 and the gate 2 can be electrically connected, or a predetermined potential can be supplied to the gate 1 or the gate 2. For example, by electrically connecting the gate 1 and the gate 2, the off-state current of the transistor 32 can be reduced in some cases. Further, by supplying a predetermined potential to the gate 1 or the gate 2, the transistor 32 can be a transistor having a high withstand voltage in some cases.

[0142] For example, FIG. 4C An example in which the transistor 31 including a back gate is used as the transistor 11 configuring the semiconductor device 10 is shown. In FIG. 4C In the present embodiment, the back gate of the transistor 31 is electrically connected to the gate.

[0143] For example, FIG. 4D An example in which the transistor 32 including two gates is used as the transistor 11 configuring the semiconductor device 10 is shown. In FIG. 4D In the present embodiment, the gate 1 of the transistor 32 is electrically connected to the gate 2.

[0144] Further, the present embodiment can be implemented in combination with other embodiments described in the present specification as appropriate.

[0145] (Embodiment 2)

[0146] In the present embodiment, an example in which the semiconductor device 10 described in the above embodiment is applied to configure a general-purpose logic circuit is described. Note that in the present specification and the like, in the case where a plurality of identical constituent elements are included, a symbol such as _1 or [2] (for example, semiconductor device 10_1, semiconductor device 10_2) is used in some cases in order to distinguish the plurality of constituent elements.

[0147] <NOT circuit and buffer circuit>

[0148] FIG. 5is a circuit diagram showing a structure example of a semiconductor device 30. The semiconductor device 30 includes two semiconductor devices 10 described in the above embodiment, and is used as a non (NOT) circuit that inverts a logic or a buffer circuit that does not invert a logic.

[0149] As FIG. 5 shown, the semiconductor device 30 includes a semiconductor device 10_1 and a semiconductor device 10_2. Note that, for explanation, in FIG. 5 , the semiconductor device 10_1 and the semiconductor device 10_2 are surrounded with dotted lines, and input / output terminals are indicated with circles on the dotted lines. In addition, potentials or signals input / output are indicated with arrows on extensions of the wirings.

[0150] As with the semiconductor device 10 described in the above embodiment, a signal SI is input to an input terminal SI_IN included in the semiconductor device 10_1, a signal SIB is input to an input terminal SIB_IN, and a signal SO is output from an output terminal SO_OUT. On the other hand, the signal SIB is input to the input terminal SI_IN included in the semiconductor device 10_2, the signal SI is input to the input terminal SIB_IN, and a signal SOB is output from an output terminal SO_OUT included in the semiconductor device 10_2.

[0151] Next, FIG. 6 is a timing chart showing an operation example of the semiconductor device 30. The signal SI, the signal SIB, and the signal SO are the same as FIG. 2 shown in the timing chart, and the signal SOB is additionally shown in FIG. 6 . The signal SI and the signal SIB in the opposite mode to the semiconductor device 10_1 are input to the semiconductor device 10_2, and thus the signal SOB is a signal obtained by inverting a logic of the signal SO.

[0152] As described above, the semiconductor device 30 is input with the signal SI and the signal SIB and outputs the signal SO and the signal SOB. The signal SIB is a signal obtained by inverting a logic of the signal SI, and the signal SOB is a signal obtained by inverting a logic of the signal SO, and thus an output terminal of the semiconductor device 30 can be electrically connected to an input terminal of another semiconductor device 30.

[0153] <Not AND (NAND) Circuit>

[0154] FIG. 7A is a circuit diagram showing a structure example of a semiconductor device 40. The semiconductor device 40 is a semiconductor device to which the semiconductor device 10 is applied, and is used as a not AND (NAND) circuit. The semiconductor device 40 includes transistors 41 to 47, and capacitor elements C41 to C43. The transistors 41 to 47 are n-channel transistors.

[0155] The semiconductor device 40 includes a wiring VSS_IN supplied with a low power supply potential VSS, a wiring VDD_IN supplied with a high power supply potential VDD, an input terminal SI1_IN to which a signal SI1 is input, an input terminal SI2_IN to which a signal SI2 is input, an input terminal SI1B_IN to which a signal SI1B is input, an input terminal SI2B_IN to which a signal SI2B is input, and an output terminal SO1_OUT from which a signal SO1 is output.

[0156] Here, the high power supply potential VDD is a potential higher than the low power supply potential VSS, and the low power supply potential VSS can also be a standard potential in the semiconductor device 40. In addition, the signal SI1, the signal SI2, the signal SI1B, and the signal SI2B are digital signals, and the potential at a high level of the signal SI1, the signal SI2, the signal SI1B, and the signal SI2B is the high power supply potential VDD, and the potential at a low level is the low power supply potential VSS. In addition, the signal SI1B is a signal obtained by logically inverting the signal SI1, and the signal SI2B is a signal obtained by logically inverting the signal SI2.

[0157] In the semiconductor device 40, one of the source and the drain of the transistor 46 is electrically connected to the wiring VSS_IN, the other of the source and the drain of the transistor 46 is electrically connected to one of the source and the drain of the transistor 47, the other of the source and the drain of the transistor 47 is electrically connected to one of the source and the drain of the transistor 43, one of the source and the drain of the transistor 44, one terminal of the capacitor element C43, and the gate of the transistor 45, and the other of the source and the drain of the transistor 43 and the other of the source and the drain of the transistor 44 are electrically connected to the wiring VDD_IN.

[0158] The gate of the transistor 46 is electrically connected to the input terminal SI2_IN, one terminal of the capacitor element C42, and the gate of the transistor 41, the gate of the transistor 47 is electrically connected to the input terminal SI1_IN, one terminal of the capacitor element C41, and the gate of the transistor 42, the gate of the transistor 43 is electrically connected to the input terminal SI1B_IN, and the gate of the transistor 44 is electrically connected to the input terminal SI2B_IN.

[0159] One of the source and the drain of the transistor 41 is electrically connected to the wiring VSS_IN, the other of the source and the drain of the transistor 41 is electrically connected to one of the source and the drain of the transistor 42, the other of the source and the drain of the transistor 42 is electrically connected to the other terminal of the capacitor element C41, the other terminal of the capacitor element C42, the other terminal of the capacitor element C43, one of the source and the drain of the transistor 45, and the output terminal SO1_OUT, and the other of the source and the drain of the transistor 45 is electrically connected to the wiring VDD_IN.

[0160] Here, a connection portion of the other of the source and drain of the transistor 47, one of the source and drain of the transistor 43, one of the source and drain of the transistor 44, one terminal of the capacitor element C43, and the gate of the transistor 45 is referred to as a node N41. Note that an operation example of the semiconductor device 40 will be described later.

[0161] <OR (NOR) CIRCUIT>

[0162] FIG. 7B FIG. 6 is a circuit diagram illustrating a structure example of a semiconductor device 50. The semiconductor device 50 is a semiconductor device to which the semiconductor device 10 is applied, and is used as an OR (NOR) circuit. The semiconductor device 50 includes transistors 51 to 57, capacitor elements C51 to C53. The transistors 51 to 57 are n-channel transistors.

[0163] The semiconductor device 50 includes a wiring VSS_IN to which a low power supply potential VSS is supplied, a wiring VDD_IN to which a high power supply potential VDD is supplied, an input terminal SI1_IN to which a signal SI1 is input, an input terminal SI2_IN to which a signal SI2 is input, an input terminal SI1B_IN to which a signal SI1B is input, an input terminal SI2B_IN to which a signal SI2B is input, and an output terminal SO2_OUT from which a signal SO2 is output. Note that description of potentials and signals is omitted in order to avoid repetition.

[0164] In the semiconductor device 50, one of the source and drain of the transistor 56 and one of the source and drain of the transistor 57 are electrically connected to the wiring VSS_IN, the other of the source and drain of the transistor 56 is electrically connected to the other of the source and drain of the transistor 57, one of the source and drain of the transistor 53, one terminal of the capacitor element C53, and the gate of the transistor 55, the other of the source and drain of the transistor 53 is electrically connected to one of the source and drain of the transistor 54, and the other of the source and drain of the transistor 54 is electrically connected to the wiring VDD_IN.

[0165] The gate of the transistor 56 is electrically connected to the input terminal SI1_IN, one terminal of the capacitor element C51, and the gate of the transistor 51, the gate of the transistor 57 is electrically connected to the input terminal SI2_IN, one terminal of the capacitor element C52, and the gate of the transistor 52, the gate of the transistor 53 is electrically connected to the input terminal SI1B_IN, and the gate of the transistor 54 is electrically connected to the input terminal SI2B_IN.

[0166] One of the source and drain of the transistor 51 and one of the source and drain of the transistor 52 are electrically connected to the wiring VSS_IN, the other of the source and drain of the transistor 51 and the other of the source and drain of the transistor 52, the other terminal of the capacitor element C51, the other terminal of the capacitor element C52, the other terminal of the capacitor element C53, one of the source and drain of the transistor 55, and the output terminal SO2_OUT are electrically connected, and the other of the source and drain of the transistor 55 is electrically connected to the wiring VDD_IN.

[0167] Here, the connection portion of the other of the source and drain of the transistor 56, the other of the source and drain of the transistor 57, one of the source and drain of the transistor 53, one terminal of the capacitor element C53, and the gate of the transistor 55 is referred to as a node N51.

[0168] <Operation Example of Semiconductor Device>

[0169] FIG. 8 is a timing chart showing an operation example of the semiconductor device 40 and the semiconductor device 50. FIG. 8 The potential of the signal SI1, the potential of the signal SI2, the potential of the signal SI1B, the potential of the signal SI2B, the potential of the signal SO1, and the potential of the signal SO2 are shown. Further, the time at which the potential of the signal SI1, the potential of the signal SI2, the potential of the signal SI1B, and the potential of the signal SI2B start to fall or the time at which the potential of the signal SO1 and the potential of the signal SO2 start to rise are indicated by the time T41 to the time T45.

[0170] At the time T41, the signal SI1 and the signal SI2 start to fall from a high level to a low level. Note that the signal SI1B is a signal obtained by inverting the signal SI1 logically, and the signal SI2B is a signal obtained by inverting the signal SI2 logically, and thus the description thereof is omitted.

[0171] In the semiconductor device 40, the transistor 41, the transistor 42, the transistor 46, and the transistor 47 start to fall from an on state to an off state, and due to the capacitive coupling through the capacitor element C41 and the capacitor element C42, the potential of the signal SO1 becomes a potential lower than the low level (low power supply potential VSS). In addition, because the transistor 43 and the transistor 44 start to fall from an off state to an on state, the potential of the node N41 rises from the low level, and the transistor 45 falls to an on state, and then the potential of the signal SO1 starts to rise. Due to the capacitive coupling through the capacitor element C43, as the potential of the signal SO1 rises, the potential of the node N41 exceeds the high power supply potential VDD and rises, and the potential of the signal SO1 rises until it becomes equal to the high power supply potential VDD.

[0172] In the semiconductor device 50, the transistor 51, the transistor 52, the transistor 56, and the transistor 57 are changed from the on state to the off state, and the potential of the signal SO2 is changed to a potential lower than the low level due to the capacitive coupling through the capacitor C51 and the capacitor C52. Further, because the transistor 53 and the transistor 54 are changed from the off state to the on state, the potential of the node N51 is raised from the low level, the transistor 55 is changed to the on state, and then the potential of the signal SO2 starts to be raised. The potential of the node N51 is raised above the high power supply potential VDD as the potential of the signal SO2 is raised due to the capacitive coupling through the capacitor C53, and the potential of the signal SO2 is raised until it is equal to the high power supply potential VDD.

[0173] At time T42, the signal SIl is changed from the low level to the high level, and the signal SI2 is kept at the low level.

[0174] In the semiconductor device 40, the transistor 42 and the transistor 47 are changed from the off state to the on state, but the transistor 41 and the transistor 46 are kept at the off state. Further, the transistor 43 is changed from the on state to the off state, but the transistor 44 is kept at the on state. Thus, the potential of the node N41 is kept at the high level, and the potential of the signal SO1 is kept at the high power supply potential VDD.

[0175] In the semiconductor device 50, the transistor 52 and the transistor 57 are kept at the off state, but the transistor 51 and the transistor 56 are changed from the off state to the on state. Further, the transistor 54 is kept at the on state, but the transistor 53 is changed from the on state to the off state. Thus, the potential of the node N51 is lowered from the high level, and the potential of the signal SO2 is lowered from the high power supply potential VDD to the low power supply potential VSS.

[0176] At time T43, the signal SIl is changed from the high level to the low level, and the signal SI2 is changed from the low level to the high level.

[0177] In the semiconductor device 40, the transistor 42 and the transistor 47 are changed from the on state to the off state, and the transistor 41 and the transistor 46 are changed from the off state to the on state. Further, the transistor 43 is changed from the off state to the on state, and the transistor 44 is changed from the on state to the off state. Thus, the potential of the node N41 is kept at the high level, and the potential of the signal SO1 is kept at the high power supply potential VDD.

[0178] In the semiconductor device 50, the transistor 51 and the transistor 56 change from the on state to the off state, and the transistor 52 and the transistor 57 change from the off state to the on state. In addition, the transistor 53 changes from the on state to the off state, and the transistor 54 changes from the off state to the on state. Thus, the potential of the node N51 remains at a low level, and the potential of the signal SO2 remains at the low power supply potential VSS.

[0179] At time T44, the signal SIl changes from a low level to a high level, and the signal SI2 remains at a high level.

[0180] In the semiconductor device 40, the transistor 42 and the transistor 47 change from the off state to the on state, and the transistor 41 and the transistor 46 remain at the on state. In addition, the transistor 43 changes from the on state to the off state, and the transistor 44 remains at the off state. Thus, the potential of the node N41 falls from a high level, and the potential of the signal SO1 falls from the high power supply potential VDD to the low power supply potential VSS.

[0181] In the semiconductor device 50, the transistor 51 and the transistor 56 change from the off state to the on state, and the transistor 52 and the transistor 57 remain at the on state. In addition, the transistor 53 changes from the on state to the off state, and the transistor 54 remains at the off state. Thus, the potential of the node N51 remains at a low level, and the potential of the signal SO2 remains at the low power supply potential VSS.

[0182] At time T45, the signal SIl and the signal SI2 change from a high level to a low level. The change in the signal SIl and the signal SI2 at time T45 is the same as that at time T41, and thus the description thereof is omitted.

[0183] As described above, the semiconductor device 40 is input with the signal SIl, the signal SI2, the signal SIlB, and the signal SI2B, and outputs the signal SO1. In other words, the semiconductor device 40 is used as a NAND circuit. In addition, the semiconductor device 50 is input with the signal SIl, the signal SI2, the signal SIlB, and the signal SI2B, and outputs the signal SO2. In other words, the semiconductor device 50 is used as a NOR circuit.

[0184] <Structure Example of Semiconductor Device>

[0185] The semiconductor device 40 and the semiconductor device 50 can be used in combination as in the semiconductor device 30 including two semiconductor devices 10.

[0186] For example, the semiconductor device 40 is represented by a symbol shown in FIG. 17A, and the semiconductor device 50 is represented by a symbol shown in FIG. 17B. FIG. 9A FIG. 9B ​The symbol shown indicates the semiconductor device 50. Also, an example of combining these semiconductor devices is described.

[0187] FIG. 9A is a diagram showing a symbol of the semiconductor device 40, and shows a wiring VSS_IN, a wiring VDD_IN, an input terminal SI1_IN, an input terminal SI2_IN, an input terminal SI1B_IN, an input terminal SI2B_IN, and an output terminal SO1_OUT for input / output.

[0188] FIG. 9B is a diagram showing a symbol of the semiconductor device 50, and shows a wiring VSS_IN, a wiring VDD_IN, an input terminal SI1_IN, an input terminal SI2_IN, an input terminal SI1B_IN, an input terminal SI2B_IN, and an output terminal SO2_OUT for input / output.

[0189] FIG. 10A is a block diagram showing an example of the structure of the semiconductor device 60. The semiconductor device 60 includes the semiconductor device 40 and the semiconductor device 50. An arrow on an extension line of a wiring indicates a potential or a signal input to or output from the semiconductor device 40 and the semiconductor device 50.

[0190] In the semiconductor device 60, a signal SI1 is input to an input terminal SI1_IN included in the semiconductor device 40, a signal SI2 is input to an input terminal SI2_IN, a signal SI1B is input to an input terminal SI1B_IN, a signal SI2B is input to an input terminal SI2B_IN, and a signal SO1 is output from an output terminal SO1_OUT. On the other hand, in the semiconductor device 60, a signal SI1B is input to an input terminal SI1_IN included in the semiconductor device 50, a signal SI2B is input to an input terminal SI2_IN, a signal SI1 is input to an input terminal SI1B_IN, a signal SI2 is input to an input terminal SI2B_IN, and a signal SO1B is output from an output terminal SO2_OUT.

[0191] Next, FIG. 11 is a timing chart showing an example of the operation of the semiconductor device 60. A signal SI1, a signal SI2, a signal SI1B, a signal SI2B, and a signal SO1 are the same as in FIG. 8 The timing chart shown in FIG. 11 is additionally shown.

[0192] The timing chart shown in FIG. 8The timing diagram illustrates that signals SI1 and SI1B, as well as SI2 and SI2B, are input to semiconductor device 50, which is included in semiconductor device 60, in the opposite manner. Therefore, when signals SI1B and SI2B are at a low level, semiconductor device 50 outputs a high-level signal SO1B from its output terminal SO2_OUT. In other words, signal SO1B is the logical inversion of signal SO1.

[0193] FIG. 10B This is a block diagram illustrating a structural example of semiconductor device 70. Semiconductor device 70 includes semiconductor device 50 and semiconductor device 40. Arrows on the extension lines of the wiring indicate potentials or signals input to or output from semiconductor device 50 and semiconductor device 40.

[0194] In semiconductor device 70, signal SI1 is input to input terminal SI1_IN, signal SI2 is input to input terminal SI2_IN, signal SI1B is input to input terminal SI1B_IN, signal SI2B is input to input terminal SI2B_IN, and signal SO2 is output from output terminal SO2_OUT. Conversely, in semiconductor device 70, signal SI1B is input to input terminal SI1_IN, signal SI2B is input to input terminal SI2_IN, signal SI1 is input to input terminal SI1B_IN, signal SI2 is input to input terminal SI2B_IN, and signal SO2B is output from output terminal SO1_OUT.

[0195] then, FIG. 12 This is a timing diagram illustrating an example of the operation of semiconductor device 70. Signals SI1, SI2, SI1B, SI2B, and SO2 are... FIG. 8 The timing diagram shown is similar, in FIG. 12 The timing diagram for signal SO2B is added below.

[0196] With and in FIG. 8 The timing diagram illustrates that signals SI1 and SI1B, as well as SI2 and SI2B, are input to semiconductor device 40, which is included in semiconductor device 70, in the opposite manner. Therefore, when signals SI1B and SI2B are high, semiconductor device 40 outputs a low-level signal SO2B from its output terminal SO1_OUT. In other words, signal SO2B is the logical inversion of signal SO2.

[0197] As described above, the semiconductor device 60 is input with the signal SI1, the signal SI2, the signal SI1B, and the signal SI2B, and outputs the signal SO1 and the signal SO1B. In addition, the semiconductor device 70 is input with the signal SI1, the signal SI2, the signal SI1B, and the signal SI2B, and outputs the signal SO2 and the signal SO2B. The signal SO1B is a signal obtained by inverting the logic of the signal SO1, and the signal SO2B is a signal obtained by inverting the logic of the signal SO2.

[0198] In other words, the semiconductor device 30, the semiconductor device 60, and the semiconductor device 70 can be electrically connected to each other, and a general-purpose logic circuit can be configured by using the semiconductor device 30, the semiconductor device 60, and the semiconductor device 70.

[0199] In addition, the present embodiment can be implemented in combination with other embodiments described in the present specification as appropriate.

[0200] (Embodiment 3)

[0201] In the present embodiment, a structure example of an OS transistor which can be used as the transistor constituting the semiconductor device 10, the transistor constituting the semiconductor device 20, the transistor constituting the semiconductor device 40, and the transistor constituting the semiconductor device 50 described in the above-described embodiments is described. Note that the OS transistor is a thin film transistor, and the transistor can be provided in a stacked manner, and thus, in the present embodiment, a structure example of a semiconductor device in which an OS transistor is provided above an Si transistor formed over a single-crystal silicon substrate is described.

[0202] <Structure Example of Semiconductor Device>

[0203] FIG. 13 The semiconductor device illustrated in FIG. 1 includes a transistor 300, a transistor 500, and a capacitor element 600. FIG. 14A is a cross-sectional view of the transistor 500 in a channel length direction, FIG. 14B is a cross-sectional view of the transistor 500 in a channel width direction, FIG. 14C is a cross-sectional view of the transistor 300 in a channel width direction.

[0204] The transistor 500 is an OS transistor including a metal oxide in a channel formation region. The transistor 500 has characteristics that a high voltage can be applied between a source and a drain, an off-state current is not likely to increase in a high-temperature environment, a ratio of an on-state current to an off-state current is large in a high-temperature environment, and the like, and thus, in the above-described embodiments, by using the transistor 500 for the semiconductor device 10, the semiconductor device 20, the semiconductor device 40, and the semiconductor device 50, the reliability of the semiconductor device can be improved.

[0205] As FIG. 13As shown, the semiconductor device described in this embodiment includes transistor 300, transistor 500, and capacitor element 600. Transistor 500 is disposed above transistor 300, and capacitor element 600 is disposed above transistor 300 and transistor 500.

[0206] The transistor 300 is disposed on the substrate 311 and includes: a conductor 316, an insulator 315, a semiconductor region 313 formed by a portion of the substrate 311; and low-resistance regions 314a and 314b used as source or drain regions.

[0207] like FIG. 14C As shown, in transistor 300, conductor 316 covers the top surface of semiconductor region 313 and the side surface in the channel width direction via insulator 315. Thus, by giving transistor 300 a Fin-type structure, the effective channel width is increased, thereby improving the on-state characteristics of transistor 300. Furthermore, since the influence of the electric field of the gate electrode can be increased, the off-state characteristics of transistor 300 can be improved.

[0208] In addition, transistor 300 can be a p-channel transistor or an n-channel transistor.

[0209] The channel formation region or its vicinity in semiconductor region 313, the low-resistance regions 314a and 314b used as source or drain regions, preferably contain semiconductors such as silicon-based semiconductors, and more preferably contain single-crystal silicon. Alternatively, materials containing Ge (germanium), SiGe (silicon-germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), etc., may be used. Silicon, by applying stress to the crystal lattice and changing the interplanar spacing to control the effective quality, can be used. Alternatively, transistor 300 may also be a HEMT (High Electron Mobility Transistor) using GaAs and GaAlAs, etc.

[0210] In the low resistance regions 314a and 314b, in addition to the semiconductor material used in the semiconductor region 313, elements such as arsenic and phosphorus that impart n-type conductivity or elements such as boron that impart p-type conductivity are also included.

[0211] The conductor 316 used as the gate electrode can be a conductive material such as silicon, a semiconductor material, a metal material, an alloy material, or a metal oxide material, which contains elements that impart n-type conductivity, such as arsenic or phosphorus, or elements that impart p-type conductivity, such as boron.

[0212] Further, since the material of the conductive body determines the work function, the Vth of the transistor can be adjusted by changing the material of the conductive body. Specifically, as the conductive body, a material such as titanium nitride or tantalum nitride is preferably used. In order to have conductivity and embeddability, a stack of a metal material such as tungsten or aluminum is preferably used as the conductive body, and in particular, tungsten is preferably used in terms of heat resistance.

[0213] Note that, FIG. 13 The transistor 300 illustrated in FIG. 3 is just an example, and the structure is not limited to the above structure, and an appropriate transistor can be used depending on the circuit structure or the driving method.

[0214] The insulator 320, the insulator 322, the insulator 324, and the insulator 326 are sequentially stacked in this order so as to cover the transistor 300.

[0215] As the insulator 320, the insulator 322, the insulator 324, and the insulator 326, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, and aluminum nitride can be used.

[0216] The insulator 322 can also be used as a planarization film for planarizing a step resulting from the transistor 300 or the like provided therebelow. For example, in order to improve the planarity of the top surface of the insulator 322, the top surface thereof can also be planarized by a planarization treatment such as a chemical mechanical polishing (CMP) method.

[0217] As the insulator 324, a film having a barrier property which can prevent hydrogen or impurities from diffusing from the substrate 311 or the transistor 300 or the like into a region where the transistor 500 is provided is preferably used.

[0218] As one example of a film having a barrier property against hydrogen, for example, silicon nitride formed by a CVD method can be used. Here, sometimes hydrogen diffuses into a semiconductor element having an oxide semiconductor such as the transistor 500, leading to a decrease in the characteristics of the semiconductor element. Thus, a film which inhibits diffusion of hydrogen is preferably provided between the transistor 500 and the transistor 300. The film which inhibits diffusion of hydrogen specifically refers to a film in which the amount of desorption of hydrogen is small.

[0219] The amount of desorption of hydrogen can be measured by a thermal desorption spectroscopy (TDS analysis) method or the like, for example. For example, in TDS analysis, when the amount of desorption converted into hydrogen atoms is converted into the amount per unit area of the insulator 324 in a range of 50 °C to 500 °C of the film surface temperature, the amount of desorption of hydrogen of the insulator 324 is 10 x 10 15 atoms / cm 2 Hereinafter, 5 x 10 15 atoms / cm 2 or more is preferable.

[0220] Note that the dielectric constant of insulator 326 is preferably lower than that of insulator 324. For example, the relative dielectric constant of insulator 326 is preferably less than 4, more preferably less than 3. For example, the relative dielectric constant of insulator 326 is preferably less than 0.7 times that of insulator 324, more preferably less than 0.6 times. By using a material with a low relative dielectric constant for the interlayer film, parasitic capacitance generated between wirings can be reduced.

[0221] Furthermore, conductors 328 and 330, which are connected to the capacitor element 600 or the transistor 500, are embedded in insulators 320, 322, 324, and 326. In addition, conductors 328 and 330 function as plugs or wiring. Note that sometimes the same reference numeral is used to indicate multiple conductors that function as plugs or wiring. Furthermore, in this specification, wiring and plugs connected to wiring can also be considered as components. That is, a portion of a conductor is sometimes used as wiring, and a portion of a conductor is sometimes used as a plug.

[0222] As materials for the plugs and wiring (conductors 328 and 330, etc.), single layers or stacks of conductive materials such as metals, alloys, metal nitrides, or metal oxides can be used. High-melting-point materials such as tungsten or molybdenum, which combine heat resistance and conductivity, are preferred; tungsten is particularly favored. Alternatively, low-resistance conductive materials such as aluminum or copper are preferred. Using low-resistance conductive materials reduces wiring resistance.

[0223] A wiring layer can also be formed on the insulator 326 and the conductor 330. For example, in FIG. 13 In the transistor 300, insulators 350, 352, and 354 are stacked sequentially. Furthermore, a conductor 356 is formed within insulators 350, 352, and 354. The conductor 356 functions as a connector or wiring for connection to the transistor 300. Moreover, the conductor 356 can be formed using the same material as conductors 328 and 330.

[0224] Furthermore, similar to insulator 324, insulator 350 preferably uses an insulator that blocks hydrogen. Additionally, conductor 356 preferably includes a conductor that blocks hydrogen. In particular, a hydrogen-blocking conductor is formed in the openings of the hydrogen-blocking insulator 350. By employing this structure, a barrier layer can be used to separate transistor 300 from transistor 500, thereby suppressing hydrogen diffusion from transistor 300 into transistor 500.

[0225] Note that, as the conductive body having a barrier property against hydrogen, for example, tantalum nitride or the like is preferably used. Further, by stacking tantalum nitride and tungsten having high conductivity, it is possible to maintain the conductivity as a wiring and to suppress diffusion of hydrogen from the transistor 300. At this time, the tantalum nitride layer having a barrier property against hydrogen is preferably in contact with the insulator 350 having a barrier property against hydrogen.

[0226] Further, a wiring layer can be formed over the insulator 354 and the conductive body 356. For example, in the case where the insulator 354 is formed of an insulator having a barrier property against hydrogen, the conductive body 356 is preferably formed of a conductive body having a barrier property against hydrogen. FIG. 13 In the case where the insulator 360, the insulator 362, and the insulator 364 are sequentially stacked, the conductive body 366 is formed in the insulator 360, the insulator 362, and the insulator 364. The conductive body 366 has a function of a plug or a wiring. Further, the conductive body 366 can be formed using the same material as the conductive body 328 and the conductive body 330.

[0227] Further, like the insulator 324, the insulator 360 is preferably formed using an insulator having a barrier property against hydrogen, for example. Further, the conductive body 366 preferably includes a conductive body having a barrier property against hydrogen. In particular, the conductive body having a barrier property against hydrogen is formed in an opening portion of the insulator 360 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, so that diffusion of hydrogen from the transistor 300 into the transistor 500 can be suppressed.

[0228] Further, a wiring layer can be formed over the insulator 364 and the conductive body 366. For example, in the case where the insulator 364 is formed of an insulator having a barrier property against hydrogen, the conductive body 366 is preferably formed of a conductive body having a barrier property against hydrogen. FIG. 13 In the case where the insulator 370, the insulator 372, and the insulator 374 are sequentially stacked, the conductive body 376 is formed in the insulator 370, the insulator 372, and the insulator 374. The conductive body 376 has a function of a plug or a wiring. Further, the conductive body 376 can be formed using the same material as the conductive body 328 and the conductive body 330.

[0229] Further, like the insulator 324, the insulator 370 is preferably formed using an insulator having a barrier property against hydrogen, for example. Further, the conductive body 376 preferably includes a conductive body having a barrier property against hydrogen. In particular, the conductive body having a barrier property against hydrogen is formed in an opening portion of the insulator 370 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, so that diffusion of hydrogen from the transistor 300 into the transistor 500 can be suppressed.

[0230] Further, a wiring layer can be formed over the insulator 374 and the conductive body 376. For example, in the case where the insulator 374 is formed of an insulator having a barrier property against hydrogen, the conductive body 376 is preferably formed of a conductive body having a barrier property against hydrogen. FIG. 13In this embodiment, the insulator 380, the insulator 382, and the insulator 384 are sequentially stacked. Further, the conductor 386 is formed in the insulator 380, the insulator 382, and the insulator 384. The conductor 386 has a function of a plug or a wiring. Further, the conductor 386 can be formed using the same material as the conductor 328 and the conductor 330.

[0231] Further, like the insulator 324, the insulator 380 is preferably formed using an insulator having a barrier property against hydrogen, for example. Further, the conductor 386 preferably includes a conductor having a barrier property against hydrogen. In particular, the conductor having a barrier property against hydrogen is formed in an opening portion of the insulator 380 having a barrier property against hydrogen. With this structure, the transistor 300 can be separated from the transistor 500 by a barrier layer, so that diffusion of hydrogen from the transistor 300 into the transistor 500 can be suppressed.

[0232] The wiring layer including the conductor 356, the wiring layer including the conductor 366, the wiring layer including the conductor 376, and the wiring layer including the conductor 386 are described above, but the semiconductor device according to the present embodiment is not limited thereto. The wiring layer like the wiring layer including the conductor 356 can be three layers or less, and the wiring layer like the wiring layer including the conductor 356 can be five layers or more.

[0233] The insulator 510, the insulator 512, the insulator 514, and the insulator 516 are sequentially stacked over the insulator 384. As any of the insulator 510, the insulator 512, the insulator 514, and the insulator 516, a substance having a barrier property against oxygen or hydrogen is preferably used.

[0234] For example, as the insulator 510 and the insulator 514, a film having a barrier property which can prevent diffusion of hydrogen or impurities from the substrate 311 or a region where the transistor 300 is provided, into a region where the transistor 500 is provided is preferably used. Thus, the insulator 510 and the insulator 514 can be formed using the same material as the insulator 324.

[0235] As one example of a film having a barrier property against hydrogen, silicon nitride formed by a CVD method can be used. Here, hydrogen is sometimes diffused into a semiconductor element having an oxide semiconductor, such as the transistor 500, resulting in a decrease in the characteristics of the semiconductor element. Thus, a film which inhibits diffusion of hydrogen is preferably provided between the transistor 500 and the transistor 300. Specifically, the film which inhibits diffusion of hydrogen is a film in which the amount of hydrogen released is small.

[0236] For example, as a film having a barrier property against hydrogen, the insulator 510 and the insulator 514 preferably use a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

[0237] In particular, aluminum oxide has a high barrier effect against impurities such as hydrogen, moisture, and the like, which do not pass through oxygen and cause a change in the electrical characteristics of the transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen, moisture, and the like from entering the transistor 500 in the manufacturing process of the transistor and after the manufacturing process. In addition, 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 of the transistor 500.

[0238] For example, the same material as the insulator 320 can be used for the insulator 512 and the insulator 516. In addition, by forming the interlayer film of a material with a low dielectric constant, the parasitic capacitance generated between wirings can be reduced. For example, a silicon oxide film, a silicon oxynitride film, or the like can be used for the insulator 512 and the insulator 516.

[0239] In addition, the conductor 518, a conductor (the conductor 503) that constitutes the transistor 500, and the like are embedded in the insulator 510, the insulator 512, the insulator 514, and the insulator 516. Further, the conductor 518 is used as a plug or a wiring connected to the capacitor 600 or the transistor 300. The conductor 518 can be formed using the same material as the conductor 328 and the conductor 330.

[0240] 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 moisture. With this structure, the transistor 300 and the transistor 500 can be separated by a layer having a barrier property against oxygen, hydrogen, and moisture, and thus the diffusion of hydrogen from the transistor 300 into the transistor 500 can be suppressed.

[0241] The transistor 500 is provided over the insulator 516.

[0242] As FIG. 14A and FIG. 14BAs shown in FIG. 5A, the transistor 500 includes the conductive object 503 embedded in the insulator 514 and the insulator 516, the insulator 520 provided over the insulator 516 and the conductive object 503, the insulator 520 provided over the insulator 520, the insulator 524 provided over the insulator 522, the oxide 530a provided over the insulator 524, the oxide 530b provided over the oxide 530a, the conductive objects 542a and 542b provided over the oxide 530b and separated from each other, the insulator 580 provided over the conductive objects 542a and 542b and formed with an opening overlapping with the conductive objects 542a and 542b, the conductive object 560 provided in the opening, the insulator 550 provided between the oxide 530b, the conductive objects 542a and 542b, and the insulator 580 and the conductive object 560, and the oxide 530c provided between the oxide 530b, the conductive objects 542a and 542b, and the insulator 580 and the insulator 550.

[0243] In addition, as shown in FIG. 5B, the insulator 544 is preferably provided between the oxide 530a, the oxide 530b, the conductive objects 542a and 542b, and the insulator 580. FIG. 14A FIG. 14B In addition, as shown in FIG. 5B, the insulator 544 is preferably provided between the oxide 530a, the oxide 530b, the conductive objects 542a and 542b, and the insulator 580. FIG. 14A FIG. 14B In addition, as shown in FIG. 5B, the insulator 544 is preferably provided between the oxide 530a, the oxide 530b, the conductive objects 542a and 542b, and the insulator 580. FIG. 14A FIG. 14B In addition, as shown in FIG. 5B, the insulator 544 is preferably provided between the oxide 530a, the oxide 530b, the conductive objects 542a and 542b, and the insulator 580.

[0244] Note that the oxide 530a, the oxide 530b, and the oxide 530c are collectively referred to as the oxide 530 in some cases below. Further, the conductive objects 542a and 542b are collectively referred to as the conductive object 542 in some cases below.

[0245] In the transistor 500, three layers of the oxide 530a, the oxide 530b, and the oxide 530c are stacked in a region where a channel is formed and its vicinity, but the present application is not limited to this. For example, a single layer of the oxide 530b, a two-layer structure of the oxide 530b and the oxide 530a, a two-layer structure of the oxide 530b and the oxide 530c, or a stacked-layer structure of four or more layers can be provided. In the transistor 500, the conductive object 560 has a two-layer structure, but the present application is not limited to this. For example, the conductive object 560 can have a single-layer structure or a stacked-layer structure of three or more layers. Note that FIG. 13 FIG. 14A FIG. 14B ​​​​​The transistor 500 shown is merely an example and is not limited to the above structure, and an appropriate transistor can be used in accordance with the circuit structure or the driving method.

[0246] Here, the conductive body 560 is used as a gate electrode of the transistor, and the conductive body 542a and the conductive body 542b are used as a source electrode or a drain electrode. As described above, the conductive body 560 is embedded in the opening of the insulator 580 and in the region between the conductive body 542a and the conductive body 542b. The arrangement of the conductive body 560, the conductive body 542a, and the conductive body 542b with respect to the opening of the insulator 580 is selected to be self-aligned. In other words, in the transistor 500, the gate electrode can be arranged self-aligned between the source electrode and the drain electrode. Thus, the conductive body 560 can be formed without providing a margin for alignment, and thus the reduction in the area occupied by the transistor 500 can be achieved. Thus, the miniaturization and high integration of the semiconductor device can be achieved.

[0247] Further, the conductive body 560 is formed self-aligned in the region between the conductive body 542a and the conductive body 542b, and thus the conductive body 560 does not include a region overlapping with the conductive body 542a and the conductive body 542b. Thus, the parasitic capacitance formed between the conductive body 560 and the conductive body 542a and the conductive body 542b can be reduced. Thus, the switching speed of the transistor 500 can be increased, and thus the transistor 500 can have a high frequency characteristic.

[0248] The conductive body 560 is sometimes used as a first gate (also referred to as a top gate) electrode. The conductive body 503 is sometimes used as a second gate (also referred to as a bottom gate) electrode. In this case, by independently changing the potential supplied to the conductive body 503 without linking it to the potential supplied to the conductive body 560, the Vth of the transistor 500 can be controlled. In particular, by supplying a negative potential to the conductive body 503, the Vth of the transistor 500 can be made greater than 0 V and the off-state current can be reduced. Thus, in the case where a negative potential is applied to the conductive body 503, the drain current at the time when the potential supplied to the conductive body 560 is 0 V can be reduced, compared to the case where no negative potential is applied to the conductive body 503.

[0249] The conductive body 503 is arranged so as to overlap with the oxide 530 and the conductive body 560. Thus, in the case where potentials are supplied to the conductive body 560 and the conductive body 503, the electric field generated from the conductive body 560 and the electric field generated from the conductive body 503 are connected, and thus the channel formation region formed in the oxide 530 can be covered. In this specification and the like, a structure of a transistor in which a channel formation region is surrounded by electric fields of a first gate electrode and a second gate electrode is referred to as a surrounded channel (S-channel) structure.

[0250] In addition, in the present specification and the like, the S-channel structure has the following characteristics: like the channel formation region, the side surface and the periphery of the oxide 530 in contact with the conductive body 542a and the conductive body 542b serving as a source electrode and a drain electrode are of the I-type. In addition, because the side surface and the periphery of the oxide 530 in contact with the conductive body 542a and the conductive body 542b are in contact with the insulator 544, like the channel formation region, it is possible to be of the I-type. Note that in the present specification and the like, the I-type can be said to be the same as the high-purity intrinsic state described later. Furthermore, the S-channel structure disclosed in the present specification and the like is different from the Fin type structure and the planar type structure. By employing the S-channel structure, it is possible to improve the resistance to the short channel effect, in other words, to realize a transistor in which the short channel effect is less likely to occur.

[0251] In addition, the conductive body 503 has the same structure as the conductive body 518, and the conductive body 503a is formed in contact with the inner wall of the opening of the insulator 514 and the insulator 516, and the conductive body 503b is formed inside the conductive body 503a.

[0252] The insulator 520, the insulator 522, the insulator 524, and the insulator 550 are used as gate insulating films.

[0253] Here, the insulator 524 in contact with the oxide 530 preferably uses an insulator containing oxygen exceeding the stoichiometric composition. In other words, it is preferable that a region of excess oxygen be formed in the insulator 524. By providing the above insulator containing excess oxygen in contact with the oxide 530, it is possible to reduce oxygen vacancies in the oxide 530, and thus it is possible to improve the reliability of the transistor 500.

[0254] Specifically, as the insulator having a region of excess oxygen, it is preferable to use an oxide material from which a part of oxygen is released by heating. The oxide from which oxygen is released by heating means that the amount of oxygen released in TDS analysis is 1.0 x 10 18 atoms / cm 3 The above, preferably 1.0 x 10 19 atoms / cm 3 The above, further preferably 2.0 x 10 19 atoms / cm 3 The above, or 3.0 x 10 20 atoms / cm 3 The above oxide film. In addition, the surface temperature of the film at the time of the above TDS analysis is preferably in the range of 100 °C or higher and 700 °C or lower, or 100 °C or higher and 400 °C or lower.

[0255] When the insulator 524 has an excess oxygen region, the insulator 522 preferably has a function of inhibiting diffusion of oxygen (e.g., oxygen atoms, oxygen molecules, or the like) (not easily allowing the above-described oxygen to pass through).

[0256] When the insulator 522 has a function of inhibiting diffusion of oxygen or impurities, oxygen contained in the oxide 530 does not diffuse to the insulator 520 side, and thus is preferable. Further, the conductor 503 can be inhibited from reacting with oxygen contained in the insulator 524 or the oxide 530.

[0257] As the insulator 522, for example, a single layer or a stack of insulators containing aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba, Sr) TiO3(BST), or the like is preferably used. When miniaturization and high integration of a transistor are performed, a problem such as a leakage current can occur due to thinning of a gate insulating film. By using a high-k material as an insulator used for a gate insulating film, the gate potential at the time of transistor operation can be reduced while the physical thickness is maintained.

[0258] In particular, an insulator containing an oxide of one or both of aluminum and hafnium, which is an insulating material having a function of inhibiting diffusion of impurities and oxygen or the like (not easily allowing the above-described oxygen to pass through), is preferably used. As the insulator containing an oxide of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like is preferably used. When the insulator 522 is formed using such a material, the insulator 522 is used as a layer for inhibiting release of oxygen from the oxide 530 or entry of impurities such as hydrogen from the surrounding portion of the transistor 500 into the oxide 530.

[0259] Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, zirconium oxide can be added to the above-described insulator. Further, the above-described insulator can be subjected to a nitriding treatment. Silicon oxide, silicon oxynitride, or silicon nitride can be further stacked on the above-described insulator.

[0260] The insulator 520 preferably has heat resistance. For example, silicon oxide and silicon oxynitride have heat resistance, and thus are preferable. Further, by combining a high-k material insulator and silicon oxide or silicon oxynitride, an insulator 520 having a stacked-layer structure with heat resistance and a high relative dielectric constant can be formed.

[0261] The insulator 520, the insulator 522, and the insulator 524 can have a stacked-layer structure of two or more layers. At this time, the stacked-layer structure is not limited to one formed using the same material, and can be a stacked-layer structure formed using different materials.

[0262] In the transistor 500, a metal oxide to be used as an oxide semiconductor is preferably used for the oxide 530 including a channel formation region. For example, an In-M-Zn oxide (element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium) or the like is preferably used as the oxide 530. Further, an In-Ga oxide or an In-Zn oxide can also be used as the oxide 530.

[0263] Further, a metal oxide having a low carrier density is preferably used as the transistor 500. In the case where the carrier density of the metal oxide is reduced, the concentration of impurities in the metal oxide can be reduced to reduce the density of defect states. In this specification and the like, a state in which the concentration of impurities and the density of defect states are both low is referred to as "highly purified intrinsic" or "substantially highly purified intrinsic". Examples of impurities in the metal oxide include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, silicon, and the like.

[0264] In particular, since hydrogen included in the metal oxide reacts with oxygen bonded to a metal atom to become water, an oxygen vacancy is sometimes formed in the metal oxide. When an oxygen vacancy is included in the channel formation region in the metal oxide, the transistor sometimes has a normally-on characteristic. Furthermore, a defect formed by entry of hydrogen into an oxygen vacancy is sometimes used as a donor to generate an electron as a carrier. In addition, part of hydrogen is sometimes bonded to oxygen bonded to a metal atom to generate an electron as a carrier. Thus, a transistor using a metal oxide including a large amount of hydrogen easily has a normally-on characteristic.

[0265] A defect formed by entry of hydrogen into an oxygen vacancy can be used as a donor of the metal oxide. However, it is difficult to quantitatively evaluate the defect. Thus, in the metal oxide, evaluation is sometimes performed using the carrier density, not the donor concentration. Thus, in this specification and the like, as a parameter of the metal oxide, the carrier density in a state where an electric field is not applied is sometimes used, not the donor concentration. In other words, the "carrier density" described in this specification and the like can also be referred to as the "donor concentration".

[0266] Thus, in the case where the metal oxide is used for the oxide 530, it is preferable to reduce hydrogen in the metal oxide as much as possible. Specifically, in the metal oxide, the concentration of hydrogen measured by secondary ion mass spectrometry (SIMS) is lower than 1 x 10 20 atoms / cm 3 , preferably lower than 1 x 10 19 atoms / cm 3 , more preferably lower than 5 x 10 18 atoms / cm 3, further preferably lower than 1 x 10 18 atoms / cm 3 By using a metal oxide in which impurities such as hydrogen are sufficiently reduced for the channel formation region of the transistor, the transistor can have stable electrical characteristics.

[0267] In addition, when a metal oxide is used as the oxide 530, the carrier density of the metal oxide of the channel formation region is preferably 1 x 10 18 cm -3 Further preferably, the carrier density is less than 1 x 10 17 cm -3 Further more preferably, the carrier density is less than 1 x 10 16 cm -3 Still further more preferably, the carrier density is less than 1 x 10 13 cm -3 Still further more preferably, the carrier density is less than 1 x 10 12 cm -3 Note that there is no particular limitation on the lower limit of the carrier density of the metal oxide of the channel formation region, and for example, it can be set to 1 x 10 -9 cm -3 .

[0268] In addition, when a metal oxide is used as the oxide 530, when the conductor 542 (the conductor 542a and the conductor 542b) is in contact with the oxide 530, oxygen in the oxide 530 is sometimes diffused into the conductor 542 and the conductor 542 is oxidized. When the conductor 542 is oxidized, the conductivity of the conductor 542 is likely to be decreased. In addition, the diffusion of oxygen in the oxide 530 into the conductor 542 can be referred to as the absorption of oxygen in the oxide 530 into the conductor 542.

[0269] Further, when oxygen in the oxide 530 is diffused into the conductor 542 (the conductor 542a and the conductor 542b), an interface between the conductor 542a and the oxide 530b and an interface between the conductor 542b and the oxide 530b can form another layer. Since the other layer contains more oxygen than the conductor 542, it is presumed that the other layer has insulating properties. At this time, the three-layer structure of the conductor 542, the other layer, and the oxide 530b can be considered to be a three-layer structure of a metal-insulator-semiconductor, which is also referred to as a MIS (Metal-Insulator-Semiconductor) structure or a diode connection structure mainly including a MIS structure.

[0270] Note that the above other layer is not limited to being formed between the conductor 542 and the oxide 530b, and for example, the other layer is sometimes formed between the conductor 542 and the oxide 530c or between the conductor 542 and the oxide 530b and between the conductor 542 and the oxide 530c.

[0271] Further, as the metal oxide used as the channel formation region in the oxide 530, a metal oxide having a band gap of 2 eV or more, preferably 2.5 eV or more is preferably used. In this way, by using a metal oxide having a wide band gap, the off-state current of the transistor can be reduced.

[0272] Further, the semiconductor material that can be used for the oxide 530 is not limited to the above-described metal oxide. The oxide 530 can also use a semiconductor material having a band gap (a semiconductor material other than a zero-bandgap semiconductor). For example, a single-element semiconductor such as silicon, a compound semiconductor such as gallium arsenide, a layered substance (also referred to as an atomic layer substance, a two-dimensional material, or the like) used as a semiconductor, or the like is preferably used as the semiconductor material. In particular, the layered substance used as a semiconductor is preferably used as the semiconductor material.

[0273] Here, in this specification and the like, a layered substance is a general term for a group of materials having a layered crystal structure. The layered crystal structure is a structure in which layers formed by covalent bonds or ionic bonds are stacked by bonding with a weaker bond such as van der Waals force than the covalent bonds or the ionic bonds. The layered substance has high conductivity in each unit layer, i.e., has high two-dimensional conductivity. By using a material used as a semiconductor and having high two-dimensional conductivity for the channel formation region, a transistor with a large on-state current can be provided.

[0274] As the layered substance, graphene, silicene, a chalcogenide, or the like is given. The chalcogenide is a compound containing a chalcogen element. Further, the chalcogen element is a general term for elements belonging to Group 16, and includes oxygen, sulfur, selenium, tellurium, polonium, and astatine. In addition, as the chalcogenide, a transition metal chalcogenide, a Group 13 chalcogenide, or the like can be given.

[0275] As the oxide 530, for example, a transition metal chalcogenide used as a semiconductor is preferably used. As the transition metal chalcogenide that can be used as the oxide 530, molybdenum sulfide (typically, MoS2), molybdenum selenide (typically, MoSe2), molybdenum telluride (typically, MoTe2), tungsten sulfide (typically, WS2), tungsten selenide (typically, WSe2), tungsten telluride (typically, WTe2), hafnium sulfide (typically, HfS2), hafnium selenide (typically, HfSe2), zirconium sulfide (typically, ZrS2), zirconium selenide (typically, ZrSe2), or the like can be given.

[0276] In the oxide 530, when the oxide 530a is provided below the oxide 530b, diffusion of impurities from a structure formed below the oxide 530a to the oxide 530b can be prevented. When the oxide 530c is provided above the oxide 530b, diffusion of impurities from a structure formed above the oxide 530c to the oxide 530b can be prevented.

[0277] Further, the oxide 530 preferably has a stacked-layer structure of a plurality of oxide layers having different atomic ratios of each metal atom. Specifically, the atomic ratio of element M in the constituent elements of the metal oxide used for the oxide 530a is preferably higher than the atomic ratio of element M in the constituent elements of the metal oxide used for the oxide 530b. Further, the atomic ratio of element M with respect to In in the metal oxide used for the oxide 530a is preferably higher than the atomic ratio of element M with respect to In in the metal oxide used for the oxide 530b. Further, the atomic ratio of In with respect to element M in the metal oxide used for the oxide 530b is preferably higher than the atomic ratio of In with respect to element M in the metal oxide used for the oxide 530a. Further, the oxide 530c can use the metal oxide used for the oxide 530a or the oxide 530b.

[0278] It is preferable that the energy of the conduction band minimum of the oxide 530a and the oxide 530c be higher than the energy of the conduction band minimum of the oxide 530b. In other words, the electron affinity of the oxide 530a and the oxide 530c is preferably lower than the electron affinity of the oxide 530b.

[0279] Here, in the junction of the oxide 530a, the oxide 530b, and the oxide 530c, the energy level of the conduction band minimum gently changes. In other words, the above case can also be expressed as the energy level of the conduction band minimum of the junction of the oxide 530a, the oxide 530b, and the oxide 530c continuously changes or continuously joins. For this reason, it is preferable to reduce the density of defect states of the mixed layer formed at the interface of the oxide 530a and the oxide 530b and the interface of the oxide 530b and the oxide 530c.

[0280] Specifically, by making the oxide 530a and the oxide 530b and the oxide 530b and the oxide 530c contain a common element (as a main component) in addition to oxygen, a mixed layer with low density of defect states can be formed. For example, in the case where the oxide 530b is an In-Ga-Zn oxide, an In-Ga-Zn oxide, a Ga-Zn oxide, and gallium oxide, or the like is preferably used as the oxide 530a and the oxide 530c.

[0281] At this time, the main path of the carriers is the oxide 530b. By making the oxide 530a and the oxide 530c have the above structure, the density of defect states of the interface of the oxide 530a and the oxide 530b and the interface of the oxide 530b and the oxide 530c can be reduced. Thus, the influence of the interface scattering on the conduction of the carriers is reduced, and the on-state current of the transistor 500 can be increased.

[0282] On the oxide 530b, a conductive body 542 (a conductive body 542a and a conductive body 542b) is provided, which is used as a source electrode and a drain electrode. As the conductive body 542, 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, an alloy including the above metal element, or an alloy combining the above metal elements, or the like is preferably used. For example, tantalum nitride, titanium nitride, a nitride including titanium and aluminum, a nitride including tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide including strontium and ruthenium, an oxide including lanthanum and nickel, or the like is preferably used. In addition, tantalum nitride, titanium nitride, a nitride including titanium and aluminum, a nitride including tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide including strontium and ruthenium, and an oxide including lanthanum and nickel are conductive materials which are not easily oxidized or materials which maintain conductivity even when absorbing oxygen, and thus are preferable.

[0283] In addition, as shown in FIG. 5B, a region 543 (a region 543a and a region 543b) is sometimes formed as a low-resistance region at the interface between the oxide 530 and the conductive body 542 and in the vicinity thereof. At this time, the region 543a is used as one of a source region and a drain region, and the region 543b is used as the other of the source region and the drain region. Furthermore, a channel formation region is formed in a region sandwiched between the region 543a and the region 543b. FIG. 14A

[0284] By forming the above-described conductive body 542 in contact with the oxide 530, the oxygen concentration of the region 543 is sometimes reduced. In addition, a metal compound layer including a component of the metal included in the conductive body 542 and the oxide 530 is sometimes formed in the region 543. In this case, the carrier density of the region 543 increases, and the region 543 becomes a low-resistance region.

[0285] The insulator 544 is provided so as to cover the conductive body 542, and oxidation of the conductive body 542 is suppressed. At this time, the insulator 544 can also be provided so as to cover the side surface of the oxide 530 and be in contact with the insulator 524.

[0286] As the insulator 544, a metal oxide including one or two or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, and magnesium, or the like can be used.

[0287] ​In particular, as the insulator 544, it is preferable to use aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like, which is an insulator containing one or both of aluminum and hafnium. In particular, hafnium aluminate has higher heat resistance than hafnium oxide film. Thus, it is less likely to be crystallized in heat treatment in a later step, and is thus preferable. Note that in the case where the conductor 542 is a material having resistance to oxidation or a material whose conductivity is not significantly reduced even if oxygen is absorbed, it is not necessary to necessarily provide the insulator 544. The insulator 544 can be designed as appropriate in accordance with the transistor characteristics required.

[0288] The insulator 550 is used as a gate insulating film. The insulator 550 is preferably arranged so as to be in contact with the inner side (top surface and side surface) of the oxide 530c. The insulator 550 is preferably formed using an insulator from which oxygen is released by heating. For example, an oxide film in which the amount of released oxygen converted into oxygen atoms in TDS analysis is 1.0 x 10 18 atoms / cm 3 The above is preferably 1.0 x 10 19 atoms / cm 3 The above is further preferably 2.0 x 10 19 atoms / cm 3 The above is 3.0 x 10 20 atoms / cm 3 The above is 3.0 x 10

[0289] Specifically, silicon oxide containing 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 a void can be used. In particular, silicon oxide and silicon oxynitride have heat resistance, and are thus preferable.

[0290] By providing an insulator from which oxygen is released by heating as the insulator 550 so as to be in contact with the top surface of the oxide 530c, oxygen can be efficiently supplied from the insulator 550 to the channel formation region of the oxide 530b through the oxide 530c. In addition, like the insulator 524, it is preferable to reduce the concentration of impurities such as water or hydrogen in the insulator 550. The thickness of the insulator 550 is preferably greater than or equal to 1 nm and less than or equal to 20 nm.

[0291] Furthermore, in order to efficiently supply the excess oxygen contained in the insulator 550 to the oxide 530, a metal oxide may be disposed between the insulator 550 and the conductor 560. This metal oxide preferably suppresses oxygen diffusion from the insulator 550 to the conductor 560. By disposing of a metal oxide that suppresses oxygen diffusion, the diffusion of excess oxygen from the insulator 550 to the conductor 560 is suppressed. In other words, the reduction of excess oxygen supplied to the oxide 530 can be suppressed. Additionally, oxidation of the conductor 560 due to excess oxygen can be suppressed. As this metal oxide, a material suitable for the insulator 544 can be used.

[0292] exist FIG. 14A and FIG. 14B In this process, the conductor 560 used as the first gate electrode has a two-layer structure, but it can also have a single-layer structure or a stacked structure of three or more layers.

[0293] As the conductor 560a, a conductive material that suppresses the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N2O, NO, NO2, etc.), and copper atoms is preferably used. Alternatively, a conductive material that suppresses the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.) is preferably used. By giving the conductor 560a the function of suppressing oxygen diffusion, the decrease in conductivity caused by the oxidation of the conductor 560b due to oxygen contained in the insulator 550 can be suppressed. As a conductive material that suppresses oxygen diffusion, tantalum, tantalum nitride, ruthenium, or ruthenium oxide are preferably used, for example.

[0294] As the conductor 560b, a conductive material with tungsten, copper, or aluminum as its main components is preferably used. Since the conductor 560b is also used for wiring, a conductor with high conductivity is preferred. For example, a conductive material with tungsten, copper, or aluminum as its main components can be used. The conductor 560b may also have a multilayer structure, for example, a multilayer structure of titanium or titanium nitride and the aforementioned conductive material can be used.

[0295] An insulator 580 is disposed on the conductor 542, separated by an insulator 544. The insulator 580 preferably has an excess oxygen region. For example, the insulator 580 preferably comprises silicon oxide, silicon oxynitride, silicon oxynitride, silicon nitride, fluorine-added silicon oxide, carbon-added silicon oxide, carbon and nitrogen-added silicon oxide, porous silicon oxide, or resin, etc. In particular, silicon oxide and silicon oxynitride are preferred due to their thermal stability. Furthermore, silicon oxide and porous silicon oxide are preferred because they readily form excess oxygen regions in subsequent processes.

[0296] The insulator 580 preferably has an excess-oxygen region. By providing the insulator 580 that releases oxygen by heating in contact with the oxide 530c, oxygen in the insulator 580 can be efficiently supplied to the oxide 530 through the oxide 530c. In addition, it is preferable to reduce the concentration of impurities such as water or hydrogen in the insulator 580.

[0297] The opening of the insulator 580 is formed so as to overlap with the region between the conductive body 542a and the conductive body 542b. Thus, the conductive body 560 is filled in the opening of the insulator 580 and the region between the conductive body 542a and the conductive body 542b.

[0298] When miniaturization of the semiconductor device is performed, it is necessary to shorten the gate length, but it is necessary to prevent a decrease in the conductivity of the conductive body 560. For this reason, in the case where the thickness of the conductive body 560 is increased, the conductive body 560 can have a shape with a high aspect ratio. In the present embodiment, since the conductive body 560 is filled in the opening of the insulator 580, even if the conductive body 560 has a shape with a high aspect ratio, collapse of the conductive body 560 does not occur in the process.

[0299] The insulator 574 is preferably provided in contact with the top surface of the insulator 580, the top surface of the conductive body 560, and the top surface of the insulator 550. By forming the insulator 574 using a sputtering method, an excess-oxygen region can be formed in the insulator 550 and the insulator 580. Thus, oxygen can be supplied from the excess-oxygen region to the oxide 530.

[0300] For example, as the insulator 574, a metal oxide containing one or two or more kinds selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, and magnesium, or the like can be used.

[0301] In particular, aluminum oxide has high barrier properties, and even a thin film of 0.5 nm or more and 3.0 nm or less can suppress diffusion of hydrogen and nitrogen. Thus, aluminum oxide formed using a sputtering method can function as a barrier film for impurities such as hydrogen while being used as an oxygen supply source.

[0302] In addition, it is preferable to provide the insulator 581 that is used as an interlayer film on the insulator 574. As with the insulator 524, it is preferable to reduce the concentration of impurities such as water or hydrogen in the insulator 581.

[0303] In addition, the conductive body 540a and the conductive body 540b are arranged in the openings formed in the insulator 581, the insulator 574, the insulator 580, and the insulator 544. The conductive body 540a and the conductive body 540b are provided so as to face each other with the conductive body 560 interposed therebetween. The conductive body 540a and the conductive body 540b have the same structure as the conductive body 546 and the conductive body 548 described later.

[0304] An insulator 582 is provided over the insulator 581. The insulator 582 is preferably formed using a substance having a barrier property against oxygen or hydrogen. Thus, the same material as the insulator 514 can be used for the insulator 582. For example, a metal oxide such as aluminum oxide, hafnium oxide, tantalum oxide, or the like is preferably used for the insulator 582.

[0305] In particular, aluminum oxide has a high barrier property against impurities such as oxygen, hydrogen, moisture, and the like, which cause a change in electric characteristics of the transistor. Thus, the use of aluminum oxide can prevent entry of impurities such as hydrogen, moisture, and the like into the transistor 500 during the manufacturing process of the transistor and after the manufacturing process. Furthermore, the use of aluminum oxide can suppress release of oxygen from the oxide included in the transistor 500. Thus, aluminum oxide is suitable for a protective film of the transistor 500.

[0306] Further, an insulator 586 is provided over the insulator 582. The same material as the insulator 320 can be used for the insulator 586. Further, by forming an interlayer film of a material having a low dielectric constant, a parasitic capacitance generated between wirings can be reduced. For example, a silicon oxide film, a silicon nitride oxide film, or the like can be used for the insulator 586.

[0307] Further, the conductive body 546 and the conductive body 548 are embedded in the insulator 520, the insulator 522, the insulator 524, the insulator 544, the insulator 580, the insulator 574, the insulator 581, the insulator 582, and the insulator 586.

[0308] The conductive body 546 and the conductive body 548 are used as a plug or a wiring connected to the capacitor 600, the transistor 500, or the transistor 300. The conductive body 546 and the conductive body 548 can be formed using the same material as the conductive body 328 and the conductive body 330.

[0309] Next, the capacitor 600 is provided over the transistor 500. The capacitor 600 includes a conductive body 610, a conductive body 620, and an insulator 630.

[0310] Further, the conductive body 612 can be provided over the conductive body 546 and the conductive body 548. The conductive body 612 is used as a plug or a wiring connected to the transistor 500. The conductive body 610 is used as an electrode of the capacitor 600. Further, the conductive body 612 and the conductive body 610 can be formed simultaneously.

[0311] As the conductive body 612 and the conductive body 610, a metal film containing an element selected from molybdenum, titanium, tantalum, tungsten, aluminum, copper, chromium, neodymium, and scandium, or a metal nitride film (tantalum nitride film, titanium nitride film, molybdenum nitride film, tungsten nitride film) containing any of the above elements can be used. Alternatively, an electrically 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 to which silicon oxide is added can be used.

[0312] In this embodiment, the conductive body 612 and the conductive body 610 have a single-layer structure, but the structure is not limited to this and can have a stacked-layer structure of two or more layers. For example, an electrically conductive body having high tightness can be formed between an electrically conductive body having barrier properties and an electrically conductive body having high conductivity. FIG. 13

[0313] The conductive body 620 is provided so as to overlap with the conductive body 610 with the insulator 630 interposed therebetween. As the conductive body 620, an electrically conductive material such as a metal material, an alloy material, or a metal oxide material can be used. It is preferable to use a high-melting-point material such as tungsten or molybdenum which has both heat resistance and conductivity, and in particular, tungsten is preferable. When the conductive body 620 is formed at the same time as another component such as a conductive body, a low-resistance metal material such as Cu (copper) or Al (aluminum) can be used.

[0314] The insulator 650 is provided over the conductive body 620 and the insulator 630. The insulator 650 can be formed using the same material as the insulator 320. Further, the insulator 650 can be used as a planarization film which covers the uneven shape of the underlying layer.

[0315] With the structure, the reliability of a semiconductor device using a transistor including an oxide semiconductor can be improved while the variation in electrical characteristics of the semiconductor device is suppressed. Further, a transistor including an oxide semiconductor which has a large on-state current can be provided. Further, a transistor including an oxide semiconductor which has a small off-state current can be provided. Further, a semiconductor device with reduced power consumption can be provided. Further, miniaturization or high integration of a semiconductor device using a transistor including an oxide semiconductor can be achieved.

[0316] <Structure Example of Transistor>

[0317] Note that the structure of the transistor 500 of the semiconductor device described in this embodiment is not limited to the above structure. Hereinafter, a structure example of the transistor 500 will be described.

[0318] <Structure Example 1 of Transistor>

[0319] Reference is made to FIG. 15A , FIG. 15B and the like.​FIG. 15C A structure example of the transistor 510A is described. FIG. 15A is a top view of the transistor 510A. FIG. 15B is a cross-sectional view of a portion indicated by a dotted line L1-L2 in FIG. 15A FIG. 15C is a cross-sectional view of a portion indicated by a dotted line W1-W2 in FIG. 15A In the top view of FIG. 15A , a part of a constituent element is omitted for clarity.

[0320] In FIG. 15A , FIG. 15B and FIG. 15C , the transistor 510A, the insulator 511 used as an interlayer film, the insulator 512, the insulator 514, the insulator 516, the insulator 580, the insulator 582, and the insulator 584 are illustrated. Further, the conductive object 546 (the conductive object 546a and the conductive object 546b) electrically connected to the transistor 510A and used as a contact plug, and the conductive object 503 used as a wiring are illustrated.

[0321] The transistor 510A includes the conductive object 560 (the conductive object 560a and the conductive object 560b) used as a first gate electrode, the conductive object 505 (the conductive object 505a and the conductive object 505b) used as a second gate electrode, the insulator 550 used as a first gate insulating film, the insulator 521, the insulator 522, the insulator 524 used as a second gate insulating film, the oxide 530 (the oxide 530a, the oxide 530b, and the oxide 530c) including a region forming a channel, the conductive object 542a used as one of a source and a drain, the conductive object 542b used as the other of the source and the drain, and the insulator 574.

[0322] Further, in the transistor 510A illustrated in FIG. 15, the oxide 530c, the insulator 550, and the conductive object 560 are provided in the opening portion provided in the insulator 580 with the insulator 574 interposed therebetween. Further, the oxide 530c, the insulator 550, and the conductive object 560 are provided between the conductive object 542a and the conductive object 542b.

[0323] The insulator 511 and the insulator 512 are used as an interlayer film.

[0324] ​As the interlayer film, a single layer or a stack of insulators such as silicon oxide, silicon oxynitride, silicon nitride oxide, aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba, Sr) TiO3(BST) can be used. Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, zirconium oxide can be added to these insulators. Further, these insulators can be subjected to nitridation treatment. A silicon oxide, silicon oxynitride, or silicon nitride layer can be stacked on the above insulator.

[0325] For example, the insulator 511 is preferably used as a barrier film for inhibiting entry of impurities such as water or hydrogen from the substrate side into the transistor 510A. Therefore, as the insulator 511, an insulating material having a function of inhibiting diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms (not easily permeable to the above impurities) is preferably used. Further, an insulating material having a function of inhibiting diffusion of oxygen (at least one of oxygen atoms, oxygen molecules, and the like) (not easily permeable to the above oxygen) is preferably used. For example, aluminum oxide or silicon nitride is preferably used as the insulator 511. With this structure, diffusion of impurities such as hydrogen and water from the side closer to the substrate than the insulator 511 to the side of the transistor 510A can be inhibited.

[0326] For example, the dielectric constant of the insulator 512 is preferably lower than that of the insulator 511. By using a material with a low dielectric constant for the interlayer film, the parasitic capacitance generated between wirings can be reduced.

[0327] The conductive body 503 is formed so as to be embedded in the insulator 512. Here, the height of the top surface of the conductive body 503 can be substantially the same as that of the top surface of the insulator 512. The conductive body 503 has a single-layer structure, but the present application is not limited to this. For example, the conductive body 503 can have a multi-layer film structure of two or more layers. As the conductive body 503, a conductive material with high conductivity in which tungsten, copper, or aluminum is a main component is preferably used.

[0328] In the transistor 510A, the conductive body 560 is used as a first gate (also referred to as a top gate) electrode. The conductive body 505 is used as a second gate (also referred to as a bottom gate) electrode. In this case, by independently changing the potential supplied to the conductive body 505 without linking it to the potential supplied to the conductive body 560, the threshold voltage of the transistor 510A can be controlled. In particular, by supplying a negative potential to the conductive body 505, the threshold voltage of the transistor 510A can be made greater than 0 V and the off-state current can be reduced. Thus, in the case where a negative potential is applied to the conductive body 505, the drain current at the time when the potential supplied to the conductive body 560 is 0 V can be reduced, compared to the case where no negative potential is applied to the conductive body 505.

[0329] In addition, for example, by overlapping the conductive body 505 over the conductive body 560, the electric field generated from the conductive body 560 and the electric field generated from the conductive body 505 are connected in a case where an electric potential is supplied to the conductive body 560 and the conductive body 505, and a channel formation region formed in the oxide 530 can be covered.

[0330] That is, the channel formation region can be electrically surrounded by the electric field of the conductive body 560 serving as the first gate electrode and the electric field of the conductive body 505 serving as the second gate electrode. In other words, like the transistor 500 described above, the transistor 510A has a surrounded channel (S-channel) structure.

[0331] Like the insulator 511 and the insulator 512, the insulator 514 and the insulator 516 are used as interlayer films. For example, the insulator 514 is preferably used as a barrier film for inhibiting entry of impurities such as water or hydrogen from the substrate side into the transistor 510A. With this structure, diffusion of impurities such as hydrogen, water, or the like from the side closer to the substrate than the insulator 514 to the side of the transistor 510A can be inhibited. For example, the dielectric constant of the insulator 516 is preferably lower than that of the insulator 514. By using a material with a low dielectric constant for the interlayer film, the parasitic capacitance generated between wirings can be reduced.

[0332] In the conductive body 505 serving as the second gate electrode, the conductive body 505a is formed in contact with the inner wall of the opening of the insulator 514 and the insulator 516, and the conductive body 505b is formed inside the conductive body 505a. Here, the height of the top surface of the conductive body 505a and the conductive body 505b can be substantially the same as the height of the top surface of the insulator 516. Note that in the transistor 510A, the conductive body 505a and the conductive body 505b are stacked, but the present application is not limited to this. For example, the conductive body 505 can have a single-layer structure or a stacked-layer structure of three or more layers.

[0333] Here, as the conductive body 505a, a conductive material having a function of inhibiting diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, copper atoms, or the like (not easy to allow the impurities to pass through) is preferably used. Alternatively, a conductive material having a function of inhibiting diffusion of oxygen (at least one of oxygen atoms, oxygen molecules, or the like, for example) (not easy to allow the oxygen to pass through) is preferably used. In this specification, the "function of inhibiting diffusion of impurities or oxygen" means a function of inhibiting diffusion of any one or all of the impurities and the oxygen.

[0334] For example, by making the conductive body 505a have a function of inhibiting diffusion of oxygen, a decrease in conductivity due to oxidation of the conductive body 505b can be inhibited.

[0335] In addition, in the case where the conductive body 505 also functions as a wiring, as the conductive body 505b, a conductive material having high conductivity, which is mainly composed of tungsten, copper, or aluminum, is preferably used. In this case, the conductive body 503 does not necessarily need to be provided. In the drawing, the conductive body 505b has a single-layer structure, but can have a stacked-layer structure, for example, a stacked-layer structure of titanium or titanium nitride and the above-described conductive material can be employed.

[0336] The insulator 521, the insulator 522, and the insulator 524 are used as a second gate insulating film.

[0337] The insulator 522 preferably has a barrier property. When the insulator 522 has a barrier property, the insulator 522 is used as a layer that inhibits impurities such as hydrogen from entering the transistor 510A from the surrounding portion of the transistor 510A.

[0338] As the insulator 522, for example, a single layer or a stacked layer of an insulator containing aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba, Sr) TiO3(BST) is preferably used. When miniaturization and high integration of a transistor are performed, a problem such as a leakage current occurs due to thinning of a gate insulating film. By using a high-k material as an insulator used for a gate insulating film, the gate potential at the time of transistor operation can be reduced while the physical thickness is maintained.

[0339] Further, the insulator 521 preferably has heat stability. For example, silicon oxide and silicon oxynitride are preferable because they have heat stability. In addition, by combining a high-k material insulator and silicon oxide or silicon oxynitride, an insulator 521 having a stacked-layer structure with heat stability and a high relative dielectric constant can be formed.

[0340] Note that in FIG. 15, the second gate insulating film has a three-layer stacked-layer structure, but can have a single layer or a stacked-layer structure of four or more layers. At this time, the stacked-layer structure is not necessarily formed using the same material, and can be formed using different materials.

[0341] The oxide 530 including a region used as a channel formation region includes an oxide 530a, an oxide 530b over the oxide 530a, and an oxide 530c over the oxide 530b. When the oxide 530a is provided under the oxide 530b, diffusion of impurities from a structure formed under the oxide 530a to the oxide 530b can be prevented. When the oxide 530c is provided over the oxide 530b, diffusion of impurities from a structure formed above the oxide 530c to the oxide 530b can be prevented. As the oxide 530, an oxide semiconductor of one of the above-described metal oxides can be used.

[0342] The oxide 530c is preferably provided in the opening portion provided in the insulator 580 with the insulator 574 interposed therebetween. When the insulator 574 has a barrier property, diffusion of impurities from the insulator 580 to the oxide 530 can be suppressed.

[0343] One of the conductive bodies 542 is used as a source electrode, and the other is used as a drain electrode.

[0344] The conductive bodies 542a and 542b can use a metal such as aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, or tungsten, or an alloy in which these elements are the main components. In particular, a metal nitride film such as tantalum nitride has a barrier property against hydrogen or oxygen and has high oxidation resistance, and thus is preferable.

[0345] Further, although the conductive bodies 542a and 542b are shown to have a single-layer structure in FIG. 15, a stacked-layer structure of two or more layers can also be employed. For example, a tantalum nitride film and a tungsten film are preferably stacked. Alternatively, a titanium film and an aluminum film can 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-magnesium-aluminum alloy film is stacked on a copper film, a two-layer structure in which a titanium film is stacked on a copper film, or a two-layer structure in which a tungsten film is stacked on a copper film can be employed.

[0346] Alternatively, a three-layer structure in which an aluminum film or a copper film is stacked on a titanium film or a titanium nitride film and a titanium film or a titanium nitride film is further formed thereon, a three-layer structure in which an aluminum film or a copper film is stacked on a molybdenum film or a molybdenum nitride film and a molybdenum film or a molybdenum nitride film is further formed thereon, or the like can be used. Alternatively, a transparent conductive material containing indium oxide, tin oxide, or zinc oxide can be used.

[0347] Further, a barrier layer can be provided on the conductive body 542. The barrier layer preferably uses a substance having a barrier property against oxygen or hydrogen. By employing this structure, oxidation of the conductive body 542 at the time of formation of the insulator 574 can be suppressed.

[0348] The barrier layer can use, for example, a metal oxide. In particular, an insulating film having a barrier property against oxygen or hydrogen such as aluminum oxide, hafnium oxide, gallium oxide, or the like is preferable. Further, silicon nitride formed by a CVD method can be used.

[0349] By including the barrier layer, the range of choice of the material of the conductive body 542 can be expanded. For example, a material having low oxidation resistance and high conductivity such as tungsten or aluminum can be used for the conductive body 542. Alternatively, a conductive body that is easy to deposit or process can be used.

[0350] The insulator 550 is used as a first gate insulating film. The insulator 550 is preferably provided in the opening portion provided in the insulator 580 with the oxide 530c and the insulator 574 interposed therebetween.

[0351] When the transistor is miniaturized and highly integrated, a problem such as a leakage current occurs due to thinning of the gate insulating film. At this time, like the second gate insulating film, the insulator 550 can have a stacked structure. By making the insulator used as the gate insulating film have a stacked structure of a high-k material and a material having thermal stability, the gate potential at the time of transistor operation can be reduced while the physical thickness is maintained. Further, a stacked structure having thermal stability and a high relative dielectric constant can be achieved.

[0352] The conductor 560 used as the first gate electrode includes a conductor 560a and a conductor 560b over the conductor 560a. Like the conductor 505a, as the conductor 560a, a conductive material having a function of suppressing diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, copper atoms, and the like is preferably used. In addition, a conductive material having a function of suppressing diffusion of oxygen (at least one of, for example, oxygen atoms, oxygen molecules, and the like) is preferably used.

[0353] When the conductor 560a has a function of suppressing diffusion of oxygen, the range of materials for the conductor 560b can be expanded. That is, by including the conductor 560a, oxidation of the conductor 560b can be suppressed, and a decrease in conductivity can be prevented.

[0354] As the conductive material having a function of suppressing diffusion of oxygen, for example, tantalum, tantalum nitride, ruthenium, or ruthenium oxide is preferably used. Further, as the conductor 560a, an oxide semiconductor which can be used for the oxide 530 can be used. In this case, by forming the conductor 560b using a sputtering method, the specific resistance of the conductor 560a can be reduced to be a conductor. This conductor can be referred to as an OC (Oxide Conductor) electrode.

[0355] As the conductor 560b, a conductive material in which tungsten, copper, or aluminum is a main component is preferably used. Since the conductor 560 is used as a wiring, a conductor having high conductivity is preferably used as the conductor 560b. For example, a conductive material in which tungsten, copper, or aluminum is a main component can be used. The conductor 560b can have a stacked structure, for example, titanium or titanium nitride and the above conductive material can be used in a stacked manner.

[0356] The insulator 574 is provided between the insulator 580 and the transistor 510A. As the insulator 574, an insulating material having a function of suppressing diffusion of impurities such as water, hydrogen, and oxygen is preferably used. For example, aluminum oxide, hafnium oxide, or the like is preferably used. Further, for example, a metal oxide such as magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, or tantalum oxide, silicon oxynitride, or silicon nitride can be used.

[0357] By including insulator 574, impurities such as water and hydrogen contained in insulator 580 can be suppressed from diffusing through oxide 530c and insulator 550 to oxide 530b. Furthermore, excess oxygen contained in insulator 580 can be suppressed from oxidizing conductor 560.

[0358] Insulators 580, 582 and 584 are used as interlayer membranes.

[0359] Similar to insulator 514, insulator 582 is preferably used as a barrier insulating film to prevent impurities such as water or hydrogen from entering transistor 510A from the outside.

[0360] Furthermore, similar to insulator 516, the dielectric constants of insulators 580 and 584 are preferably lower than those of insulator 582. By using a material with a lower dielectric constant for the interlayer film, parasitic capacitance generated between wirings can be reduced.

[0361] In addition, transistor 510A can also be electrically connected to other components via plugs or wiring such as conductor 546 embedded in insulators 580, 582 and 584.

[0362] Similarly to conductor 505, conductor 546 can be made of a single layer or a stack of conductive materials such as metals, alloys, metal nitrides, or metal oxides. For example, high-melting-point materials such as tungsten or molybdenum, which combine heat resistance and conductivity, are preferred. Alternatively, low-resistance conductive materials such as aluminum or copper are preferred. Using low-resistance conductive materials reduces wiring resistance.

[0363] For example, by using a stacked structure of tantalum nitride, which is a conductor that blocks hydrogen and oxygen, and tungsten, which has high conductivity, as conductor 546, the diffusion of impurities from the outside can be suppressed while maintaining the conductivity of the wiring.

[0364] By having the above structure, a semiconductor device using an oxide semiconductor transistor with a large on-state current can be provided. Alternatively, a semiconductor device using an oxide semiconductor transistor with a small off-state current can be provided. Alternatively, a semiconductor device that achieves stable electrical characteristics while suppressing variations in electrical characteristics can be provided, thereby improving reliability.

[0365] <Example 2 of transistor structure>

[0366] Reference FIG. 16A , FIG. 16B and FIG. 16C This section provides an example illustrating the structure of the 510B transistor. FIG. 16A This is a top view of transistor 510B. FIG. 16B Is FIG. 16AA cross-sectional view of a portion indicated by a dotted line L1-L2 in FIG. 5B. FIG. 16C is FIG. 16A A cross-sectional view of a portion indicated by a dotted line W1-W2 in FIG. 5B. In FIG. 16A In a plan view, a part of a constituent element is omitted for clarity.

[0367] The transistor 510B is a modification example of the transistor 510A. Thus, in order to prevent repetitive explanation, only the difference from the transistor 510A will be described.

[0368] The transistor 510B includes a region where the conductive body 542 (the conductive body 542a and the conductive body 542b) and the oxide 530c, the insulator 550, and the conductive body 560 overlap with each other. With this structure, a transistor with a large on-state current can be provided. Further, a transistor with high controllability can be provided.

[0369] The conductive body 560 used as the first gate electrode includes the conductive body 560a and the conductive body 560b over the conductive body 560a. As the conductive body 560a, a conductive material having a function of suppressing diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms is preferably used, like the conductive body 505a. Further, a conductive material having a function of suppressing diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, and the like) is preferably used.

[0370] When the conductive body 560a has a function of suppressing diffusion of oxygen, the range of materials for the conductive body 560b can be expanded. That is, by including the conductive body 560a, oxidation of the conductive body 560b can be suppressed, and a decrease in conductivity can be prevented.

[0371] Further, the insulator 574 is preferably provided so as to cover the top surface and the side surface of the conductive body 560, the side surface of the insulator 550, and the side surface of the oxide 530c. As the insulator 574, an insulating material having a function of suppressing diffusion of impurities such as water or hydrogen and oxygen is preferably used. For example, aluminum oxide, hafnium oxide, or the like is preferably used. Further, for example, a metal oxide such as magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, or tantalum oxide, silicon oxynitride, or silicon nitride can be used.

[0372] By providing the insulator 574, oxidation of the conductive body 560 can be suppressed. Further, by including the insulator 574, diffusion of impurities such as water or hydrogen included in the insulator 580 to the transistor 510B can be suppressed.

[0373] Further, an insulator 576 (an insulator 576a and an insulator 576b) having a barrier property can be provided between the conductive body 546 and the insulator 580. By providing the insulator 576, oxygen of the insulator 580 can be prevented from reacting with the conductive body 546 and causing oxidation of the conductive body 546.

[0374] In addition, by providing the insulator 576 having barrier properties, the range of materials for the conductive body of the plug or wiring can be expanded. For example, by using a metal material having a property of absorbing oxygen and having high conductivity as the conductive body 546, a semiconductor device with low power consumption can be provided. Specifically, a material with low oxidation resistance and high conductivity such as tungsten or aluminum can be used. In addition, for example, a conductive body which is easy to deposit or process can be used.

[0375] Structure Example 3 of Transistor

[0376] With reference to FIG. 17A , FIG. 17B and FIG. 17C a structure example of the transistor 510C is described. FIG. 17A is a top view of the transistor 510C. FIG. 17B is a cross-sectional view of a portion indicated by a dotted line L1-L2 in FIG. 17A . FIG. 17C is a cross-sectional view of a portion indicated by a dotted line W1-W2 in FIG. 17A . In the top view of FIG. 17A , a part of a constituent element is omitted for clarity.

[0377] The transistor 510C is a modification example of the transistor 510A. Thus, in order to prevent repetitive explanation, mainly the difference from the transistor 510A is described.

[0378] The transistor 510C illustrated in FIG. 17 is provided with the conductive body 547a between the conductive body 542a and the oxide 530b and the conductive body 547b between the conductive body 542b and the oxide 530b. Here, the conductive body 542a (the conductive body 542b) has a region which extends beyond the top surface of the conductive body 547a (the conductive body 547b) and the side surface of the conductive body 560 side and is in contact with the top surface of the oxide 530b. Here, as the conductive body 547, a conductive body which can be used for the conductive body 542 can be used. Further, the thickness of the conductive body 547 is preferably larger than that of the conductive body 542 at least.

[0379] Since the transistor 510C illustrated in FIG. 17 has the above structure, the conductive body 542 can be positioned close to the conductive body 560 compared with the transistor 510A. Alternatively, the end portion of the conductive body 542a and the end portion of the conductive body 542b can overlap with the conductive body 560. Thus, the effective channel length of the transistor 510C can be reduced, and the on-state current and the frequency characteristics can be improved.

[0380] In addition, the conductive body 547a (the conductive body 547b) preferably overlaps the conductive body 542a (the conductive body 542b). With this structure, at the time of etching for forming an opening of the conductive body 546a (the conductive body 546b), the conductive body 547a (the conductive body 547b) serves as an etching stopper layer and over-etching of the oxide 530b can be prevented.

[0381] Further, in the transistor 510C illustrated in FIG. 17, the insulator 545 can be provided in contact with the insulator 544. The insulator 544 is preferably used as a barrier insulating film for inhibiting entry of impurities such as water or hydrogen or excess oxygen from the insulator 580 side into the transistor 510C. As the insulator 545, an insulator which can be used for the insulator 544 can be used. Further, as the insulator 544, for example, an insulator such as aluminum nitride, titanium aluminum nitride, titanium nitride, silicon nitride, or silicon oxynitride can be used.

[0382] In addition, in the transistor 510C illustrated in FIG. 17, unlike the transistor 510A illustrated in FIG. 15, the conductive body 505 can have a single-layer structure. At this time, an insulating film which becomes the insulator 516 can be formed over the conductive body 505 which has been patterned, and the top portion of the insulating film can be removed by a CMP method or the like until the top surface of the conductive body 505 is exposed. Here, the planarity of the top surface of the conductive body 505 is preferably improved. For example, the average surface roughness (Ra) of the top surface of the conductive body 505 can be 1 nm or less, preferably 0.5 nm or less, and further preferably 0.3 nm or less. By this means, the planarity of the insulating layer formed over the conductive body 505 can be improved, and the crystallinity of the oxide 530b and the oxide 530c can be improved.

[0383] <Structure Example 4 of Transistor>

[0384] Reference FIG. 18A , FIG. 18B and FIG. 18C A structure example of the transistor 510D will be described. FIG. 18A is a top view of the transistor 510D. FIG. 18B is a cross-sectional view of a portion indicated by a dotted line L1-L2 in FIG. 18A FIG. 18C is a cross-sectional view of a portion indicated by a dotted line W1-W2 in FIG. 18A In the top view of FIG. 18A , a part of a constituent element is omitted for clarity.

[0385] The transistor 510D is a modification example of the above transistor. Thus, in order to prevent repetitive description, only the difference from the above transistor will be described.

[0386] In FIGS. 18A-18C ​In the case where the conductive body 505 having the function of the second gate is used as a wiring without the conductive body 503, an insulator 550 is included over the oxide 530c, and a metal oxide 552 is included over the insulator 550. Further, a conductive body 560 is included over the metal oxide 552, and an insulator 570 is included over the conductive body 560. Further, an insulator 571 is included over the insulator 570.

[0387] The metal oxide 552 preferably has a function of inhibiting diffusion of oxygen. By providing the metal oxide 552 which inhibits diffusion of oxygen between the insulator 550 and the conductive body 560, diffusion of oxygen to the conductive body 560 is inhibited. In other words, reduction in the amount of oxygen supplied to the oxide 530 can be inhibited. In addition, oxidation of the conductive body 560 due to oxygen can be inhibited.

[0388] In addition, the metal oxide 552 can be used as part of the first gate. For example, an oxide semiconductor which can be used as the oxide 530 can be used as the metal oxide 552. In that case, by forming the conductive body 560 using a sputtering method, the resistance value of the metal oxide 552 can be reduced to be a conductive layer. This can be referred to as an OC (Oxide Conductor) electrode.

[0389] In addition, the metal oxide 552 is sometimes used as part of a gate insulating film. Thus, in the case where silicon oxide or silicon oxynitride or the like is used for the insulator 550, a metal oxide which is a high-k material having a high relative dielectric constant is preferably used as the metal oxide 552. By employing such a stacked structure, a stacked structure having heat resistance and a high relative dielectric constant can be formed. Thus, the gate potential applied at the time of transistor operation can be reduced while the physical thickness is kept. In addition, the equivalent oxide thickness (EOT) of an insulating layer used as a gate insulating film can be reduced.

[0390] Although the metal oxide 552 in the transistor 510D is shown as a single-layer structure, a stacked structure of two or more layers can be employed. For example, a metal oxide used as part of a gate electrode and a metal oxide used as part of a gate insulating film can be stacked.

[0391] When the metal oxide 552 is used as the gate electrode, the on-state current of the transistor 510D can be increased without reducing the effect of the electric field from the conductor 560. In addition, when the metal oxide 552 is used as the gate insulating film, the leakage current between the conductor 560 and the oxide 530 can be suppressed by keeping the distance between the conductor 560 and the oxide 530 by the physical thickness of the insulator 550 and the metal oxide 552. Thus, by providing the stacked structure of the insulator 550 and the metal oxide 552, the physical distance between the conductor 560 and the oxide 530 and the electric field strength from the conductor 560 to the oxide 530 can be easily adjusted.

[0392] Specifically, as the metal oxide 552, an oxide semiconductor that can be used for the oxide 530 is made low-resistance, which can be used as the metal oxide 552. Alternatively, a metal oxide containing one or a plurality of kinds of metal selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, and magnesium, and the like can be used.

[0393] In particular, it is preferable to use aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like as the insulating layer containing an oxide of one or both of aluminum and hafnium. In particular, hafnium aluminate has higher heat resistance than hafnium oxide film. Thus, it is not easily crystallized in heat treatment in a later step, and is thus preferable. Note that the metal oxide 552 is not an essential component and can be designed as appropriate in accordance with the transistor characteristics required.

[0394] As the insulator 570, an insulating material having a function of suppressing the passage of impurities such as water or hydrogen and oxygen is preferably used. For example, aluminum oxide, hafnium oxide, or the like is preferably used. Thus, the conductor 560 can be prevented from being oxidized by oxygen from above the insulator 570. In addition, the passage of impurities such as water or hydrogen from above the insulator 570 into the oxide 530 through the conductor 560 and the insulator 550 can be suppressed.

[0395] The insulator 571 is used as a hard mask. By providing the insulator 571, the conductor 560 can be processed so that the side surface of the conductor 560 is substantially perpendicular to the substrate surface, specifically, the angle formed by the side surface of the conductor 560 and the substrate surface is 75 degrees or more and 100 degrees or less, preferably, 80 degrees or more and 95 degrees or less.

[0396] In addition, the insulator 571 can also function as a barrier layer by using an insulating material having a function of suppressing the passage of impurities such as water or hydrogen and oxygen as the insulator 571. In that case, the insulator 570 can not be provided.

[0397] By using the insulator 571 as a hard mask, a portion of the insulator 570, the conductor 560, the metal oxide 552, the insulator 550, and the oxide 530c is selectively removed, the side surfaces thereof can be aligned approximately, and a portion of the surface of the oxide 530b is exposed.

[0398] Further, the transistor 510D has a region 531a and a region 531b in a portion of the surface of the exposed oxide 530b. One of the region 531a and the region 531b is used as a source region, and the other is used as a drain region.

[0399] The region 531a and the region 531b can be formed, for example, by introducing an impurity element such as phosphorus or boron into the surface of the exposed oxide 530b by an ion implantation method, an ion doping method, a plasma immersion ion implantation method, or plasma treatment.

[0400] Further, the region 531a and the region 531b can be formed by forming a metal film after a portion of the surface of the oxide 530b is exposed, and then performing heat treatment to diffuse an element included in the metal film into the oxide 530b.

[0401] The region of the oxide 530b into which the impurity element is introduced has a lower resistivity. Thus, the region 531a and the region 531b are sometimes referred to as an "impurity region" or a "low-resistance region".

[0402] The region 531a and the region 531b can be formed self-aligned by using the insulator 571 and / or the conductor 560 as a mask. Thus, the region 531a and / or the region 531b do not overlap with the conductor 560, and parasitic capacitance can be reduced. Further, a bias region is not formed between the channel formation region and the source / drain region (the region 531a or the region 531b). By forming the region 531a and the region 531b self-aligned, an increase in on-state current, a decrease in threshold voltage, an increase in operating frequency, and the like can be achieved.

[0403] Further, in order to further reduce off-state current, a bias region can be provided between the channel formation region and the source / drain region. The bias region is a region with a high resistivity and is a region to which the introduction of the above impurity element is not performed. The bias region can be formed by performing the introduction of the above impurity element after the formation of the insulator 575. In this case, like the insulator 571, the insulator 575 is used as a mask. Thus, a region of the oxide 530b overlapping with the insulator 575 is not introduced with the impurity element, and thus the resistivity of the region can be kept high.

[0404] Further, the transistor 510D includes an insulator 575 on a side surface of the insulator 570, the conductor 560, the metal oxide 552, the insulator 550, and the oxide 530c. The insulator 575 is preferably an insulator with a low relative dielectric constant. For example, silicon oxide, 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, silicon oxide having a void, or resin is preferably used as the insulator 575. In particular, when silicon oxide, silicon oxynitride, silicon nitride oxide, or silicon oxide having a void is used as the insulator 575, an excess oxygen region can be easily formed in the insulator 575 in a later step, and is thus preferable. Further, silicon oxide and silicon oxynitride have heat resistance, and are thus preferable. Furthermore, the insulator 575 preferably has a function of diffusing oxygen.

[0405] Further, the transistor 510D includes an insulator 575 on a side surface of the insulator 570, the conductor 560, the metal oxide 552, the insulator 550, and the oxide 530c. The insulator 575 is preferably an insulator with a low relative dielectric constant. For example, silicon oxide, 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, silicon oxide having a void, or resin is preferably used as the insulator 575. In particular, when silicon oxide, silicon oxynitride, silicon nitride oxide, or silicon oxide having a void is used as the insulator 575, an excess oxygen region can be easily formed in the insulator 575 in a later step, and is thus preferable. Further, silicon oxide and silicon oxynitride have heat resistance, and are thus preferable. Furthermore, the insulator 575 preferably has a function of diffusing oxygen.

[0406] An oxide film formed by a sputtering method sometimes extracts hydrogen from a structure to be formed. Thus, the hydrogen concentration of the oxide 530 and the insulator 575 can be reduced because the insulator 574 absorbs hydrogen and water from the oxide 530 and the insulator 575.

[0407] Structure Example 5 of Transistor

[0408] Reference FIGS. 19A-19C A structure example of the transistor 510E will be described. FIG. 19A is a top view of the transistor 510E. FIG. 19B is a cross-sectional view of a portion indicated by dot-and-dash lines L1-L2 in FIG. 19A FIG. 19C is a cross-sectional view of a portion indicated by dot-and-dash lines W1-W2 in FIG. 19A In the top view of FIG. 19A , part of a component is omitted for clarity.

[0409] The transistor 510E is a modification example of the above transistor. Thus, a difference from the above transistor will be mainly described in order to prevent repetitive description.

[0410] In FIGS. 19A-19C , a portion of a surface of the exposed oxide 530b includes a region 531a and a region 531b without the conductor 542. One of the region 531a and the region 531b is used as a source region and the other is used as a drain region. Further, an insulator 573 is included between the oxide 530b and the insulator 574.

[0411] ​The regions 531 (regions 531a and 531b) shown in Fig. 19 are regions in which the oxide 530b is added with the following element. The regions 531 can be formed, for example, using dummy gates.

[0412] Specifically, a dummy gate is provided on the oxide 530b, the dummy gate is used as a mask, and the oxide 530b is added with an element that makes the oxide 530b low-resistance. That is, the element is added to the regions of the oxide 530b that do not overlap with the dummy gate, thereby forming the regions 531. As the method of adding the element, ion implantation in which an ionized source gas is mass-separated and added, ion doping in which an ionized source gas is not mass-separated and added, plasma immersion ion implantation, and the like can be used.

[0413] In addition, as the element that makes the oxide 530b low-resistance, boron or phosphorus is typical. In addition, hydrogen, carbon, nitrogen, fluorine, sulfur, chlorine, titanium, a rare gas, and the like can be used. As typical examples of the rare gas, helium, neon, argon, krypton, xenon, and the like are given. The concentration of the element can be measured using SIMS or the like.

[0414] In particular, boron and phosphorus can be used, for example, using the apparatus of a low-temperature polysilicon production line, and are therefore preferable. Existing equipment can be used, and thus equipment investment can be reduced.

[0415] Next, an insulating film that becomes the insulator 573 and an insulating film that becomes the insulator 574 can also be formed on the oxide 530b and the dummy gate. By laminating the insulating film that becomes the insulator 573 and the insulating film that becomes the insulator 574, a region in which the regions 531 overlap with the oxide 530c and the insulator 550 can be provided.

[0416] Specifically, an insulating film that becomes the insulator 580 is provided on the insulating film that becomes the insulator 574, and then the insulating film that becomes the insulator 580 is subjected to CMP processing, and a portion of the insulating film that becomes the insulator 580 is removed, and the dummy gate is exposed. Next, when the dummy gate is removed, a portion of the insulator 573 that is in contact with the dummy gate is preferably also removed. Thus, on the side surface of an opening portion provided in the insulator 580, the insulator 574 and the insulator 573 are exposed, and on the bottom surface of the opening portion, a portion of the regions 531 provided in the oxide 530b is exposed. Next, an oxidized film that becomes the oxide 530c, an insulating film that becomes the insulator 550, and a conductive film that becomes the conductor 560 are sequentially formed in the opening portion, and then a portion of the oxidized film that becomes the oxide 530c, the insulating film that becomes the insulator 550, and the conductive film that becomes the conductor 560 are removed until the insulator 580 is exposed using CMP processing or the like, and thus the transistor shown in Fig. 19 can be formed.

[0417] Note that it is not necessarily required to provide the insulator 573 and the insulator 574. The insulator 573 and the insulator 574 are provided as appropriate depending on the transistor characteristics needed.

[0418] The transistor illustrated in FIG. 19 can be manufactured using a conventional apparatus and does not include the conductive body 542, which can reduce the cost.

[0419] <Structure Example 6 of Transistor>

[0420] Reference FIGS. 20A-20C A structure example of the transistor 510F is described below. FIG. 20A is a top view of the transistor 510F. FIG. 20B is a cross-sectional view of a portion indicated by a dotted line L1-L2 in FIG. 20A FIG. 20C is a cross-sectional view of a portion indicated by a dotted line W1-W2 in FIG. 20A In the top view of the transistor 510F, part of the components is omitted for clarity. FIG. 20A

[0421] The transistor 510F is a modification example of the transistor 510A. Thus, the difference from the above transistor is mainly described below in order to prevent repetitive description.

[0422] In the transistor 510A, part of the insulator 574 is provided in the opening portion in the insulator 580 to cover the side surface of the conductive body 560. In the transistor 510F, on the other hand, the opening is formed by removing part of the insulator 580 and part of the insulator 574.

[0423] Further, an insulator 576 (an insulator 576a and an insulator 576b) having barrier properties can be provided between the conductive body 546 and the insulator 580. By providing the insulator 576, the reaction of oxygen in the insulator 580 with the conductive body 546 can be suppressed, which prevents the conductive body 546 from being oxidized.

[0424] ​​Furthermore, when using an oxide semiconductor as oxide 530, a stacked structure of multiple oxide layers with different atomic ratios of each metal atom is preferably adopted. Specifically, in the metal oxide used for oxide 530a, the atomic ratio of element M in the constituent elements is preferably greater than that in the metal oxide used for oxide 530b. Furthermore, in the metal oxide used for oxide 530a, the atomic ratio of element M relative to In is preferably greater than that in the metal oxide used for oxide 530b. Furthermore, in the metal oxide used for oxide 530b, the atomic ratio of In relative to element M is preferably greater than that in the metal oxide used for oxide 530a. Additionally, oxide 530c can use a metal oxide that can be used for oxide 530a or oxide 530b.

[0425] Oxides 530a, 530b, and 530c are preferably crystalline, and in particular, CAAC-OS is preferred. Crystalline oxides such as CAAC-OS have a highly crystalline and dense structure with few impurities and defects (such as oxygen vacancies). Therefore, the extraction of oxygen from oxide 530b from the source or drain electrode can be suppressed. Thus, even with heat treatment, the extraction of oxygen from oxide 530b can be reduced, and the transistor 510F is also stable against the high temperatures (so-called thermal budget) in the manufacturing process.

[0426] Alternatively, one or both of oxides 530a and 530c may be omitted. Oxide 530 may also be a single layer of oxide 530b. When oxide 530a, oxide 530b, and oxide 530c are used as oxide 530, it is preferable that the conduction band bottom energy of oxides 530a and 530c is higher than that of oxide 530b. In other words, the electron affinity of oxides 530a and 530c is preferably lower than that of oxide 530b. In this case, oxide 530c is preferably a metal oxide that can be used for oxide 530a. Specifically, in the metal oxide used for oxide 530c, the atomic ratio of element M in the constituent elements is preferably greater than that of element M in the constituent elements of the metal oxide used for oxide 530b. Furthermore, in the metal oxide used for oxide 530c, the atomic ratio of element M relative to In is preferably greater than that of element M relative to In in the metal oxide used for oxide 530b. Furthermore, in the metal oxide used for oxide 530b, the ratio of the number of In atoms relative to element M is preferably greater than the ratio of the number of In atoms relative to element M in the metal oxide used for oxide 530c.

[0427] Here, at the junction of oxides 530a, 530b, and 530c, the energy level at the conduction band bottom changes gradually. In other words, the above situation can also be expressed as the energy level at the conduction band bottom of the junction of oxides 530a, 530b, and 530c changing continuously or continuously joining. For this purpose, it is preferable to reduce the defect state density of the mixed layer formed at the interface between oxides 530a and 530b, and at the interface between oxides 530b and 530c.

[0428] Specifically, by including a common element (as the main component) besides oxygen in oxides 530a and 530b, and in oxides 530b and 530c, a mixed layer with low defect state density can be formed. For example, when oxide 530b is an In-Ga-Zn oxide, In-Ga-Zn oxide, Ga-Zn oxide, and gallium oxide can be used as oxides 530a and 530c. Furthermore, oxide 530c can have a stacked structure. For example, a stacked structure of In-Ga-Zn oxide and Ga-Zn oxide on the In-Ga-Zn oxide can be used, or a stacked structure of In-Ga-Zn oxide and gallium oxide on the In-Ga-Zn oxide can be used. In other words, as oxide 530c, a stacked structure of In-Ga-Zn oxide and an oxide not containing In can also be used.

[0429] Specifically, for oxide 530a, a metal oxide with an In:Ga:Zn ratio of 1:3:4 or 1:1:0.5 is acceptable. Furthermore, for oxide 530b, a metal oxide with an In:Ga:Zn ratio of 4:2:3 or 3:1:2 is acceptable. Additionally, for oxide 530c, a metal oxide with an In:Ga:Zn ratio of 1:3:4, 4:2:3, 2:1, or 2:5 is acceptable. Furthermore, as specific examples of oxide 530c having a stacked structure, we can cite stacked structures with In:Ga:Zn = 4:2:3 [atomic ratio] and Ga:Zn = 2:1 [atomic ratio], stacked structures with In:Ga:Zn = 4:2:3 [atomic ratio] and Ga:Zn = 2:5 [atomic ratio], and stacked structures with In:Ga:Zn = 4:2:3 [atomic ratio] and gallium oxide, etc.

[0430] At this point, the primary pathway for charge carriers is oxide 530b. By giving oxides 530a and 530c the aforementioned structure, the defect state density at the interface between oxides 530a and 530b, and at the interface between oxides 530b and 530c, can be reduced. Therefore, the influence of interface scattering on charge carrier conduction is reduced, resulting in a large on-state current and high frequency characteristics for transistor 510F. Furthermore, when oxide 530c has a stacked structure, it is expected to reduce the defect state density at the interface between oxides 530b and 530c, and suppress the diffusion of constituent elements of oxide 530c to the insulator 550 side. More specifically, when oxide 530c has a stacked structure, because the oxide without In is located on top of the stacked structure, the diffusion of In to the insulator 550 side can be suppressed. Since insulator 550 is used as the gate insulator, the diffusion of In within it leads to poor transistor characteristics. Thus, by giving oxide 530c a stacked structure, a highly reliable semiconductor device can be provided.

[0431] The oxide 530 preferably uses a metal oxide that is used as an oxide semiconductor. For example, the metal oxide that will form the channel region of the oxide 530 preferably uses a metal oxide with a band gap of 2 eV or more, and more preferably 2.5 eV or more. In this way, by using a metal oxide with a wider band gap, the off-state current of the transistor can be reduced. By employing such a transistor, a low-power semiconductor device can be provided.

[0432] <Example 7 of transistor structure>

[0433] use FIG. 21A and FIG. 21B This section describes a structural example of transistor 510G. Transistor 510G is a variation of transistor 500. Therefore, to avoid repetition, the differences from the transistor described above will be primarily explained. Note that... FIG. 21A and FIG. 21B The structure shown can also be used for other transistors included in a semiconductor device of one aspect of the present invention, such as transistor 300.

[0434] FIG. 21A This is a cross-sectional view of the 510G transistor along its channel length. FIG. 21B This is a cross-sectional view of the 510G transistor along its channel width. FIG. 21A and FIG. 21B The transistor 510G with the structure shown is FIG. 14A and FIG. 14B The transistor 500 shown differs in that it includes insulators 402 and 404. Furthermore, compared to... FIG. 14A and FIG. 14BThe difference in the transistor 500 shown is that an insulator 551 is disposed in contact with the side of conductor 540a, and an insulator 551 is disposed in contact with the side of conductor 540b. Furthermore, with... FIG. 14A and FIG. 14B The difference in the transistor 500 shown is that it does not include the insulator 520.

[0435] exist FIG. 21A and FIG. 21B In the transistor 510G shown, an insulator 402 is provided on the insulator 512. In addition, an insulator 404 is provided on the insulator 574 and the insulator 402.

[0436] exist FIG. 22 and FIG. 21A In the transistor 510G shown, insulators 514, 516, 522, 524, 544, 580, and 574 are patterned, and insulator 404 covers them. That is, insulator 404 is in contact with the top surface of insulator 574, the side surface of insulator 574, the side surface of insulator 580, the side surface of insulator 544, the side surface of insulator 524, the side surface of insulator 522, the side surface of insulator 516, the side surface of insulator 514, and the top surface of insulator 402. Thus, oxide 530 and the like are separated from the outside by insulators 404 and 402.

[0437] The insulators 402 and 404 preferably have a high ability to suppress the diffusion of hydrogen (e.g., at least one of hydrogen atoms, hydrogen molecules, etc.) or water molecules. For example, silicon nitride or silicon oxynitride, materials with high hydrogen barrier properties, are preferably used as insulators 402 and 404. As a result, since the diffusion of hydrogen and the like into oxide 530 can be suppressed, the degradation of transistor 510G's characteristics can be suppressed. Therefore, the reliability of the semiconductor device according to one aspect of the present invention can be improved.

[0438] Insulator 551 is disposed in contact with insulators 581, 404, 574, 580, and 544. Insulator 551 preferably has the function of suppressing the diffusion of hydrogen or water molecules. For example, insulators such as silicon nitride, aluminum oxide, or silicon oxynitride, which have high hydrogen barrier properties, are preferably used as insulator 551. In particular, silicon nitride is a material with high hydrogen barrier properties and is therefore preferred for insulator 551. By using a material with high hydrogen barrier properties as insulator 551, the diffusion of impurities such as water or hydrogen from insulator 580 through conductors 540a and 540b to oxide 530 can be suppressed. Furthermore, the absorption of oxygen contained in insulator 580 by conductors 540a and 540b can be suppressed. Thus, the reliability of the semiconductor device according to one aspect of the present invention can be improved.

[0439] FIG. 21B This shows that transistors 500 and 300 have FIG. 23A and FIG. 23B A cross-sectional view of an example of the structure of a semiconductor device shown. An insulator 551 is provided on the side of the conductor 546.

[0440] FIG. 21A and FIG. 21B yes FIG. 23A and FIG. 23B The example shown is a modified version of the transistor. FIG. 23A It is a cross-sectional view along the channel length of the transistor. FIG. 23B It is a cross-sectional view of the transistor along the channel width direction. FIG. 21A and FIG. 21B The transistor shown is FIG. 14A and FIG. 14B The difference shown in the transistor is that the oxide 530c has a two-layer structure of oxide 530c1 and oxide 530c2.

[0441] Oxide 530c1 is in contact with the top surface of insulator 524, the side surface of oxide 530a, the top surface and side surface of oxide 530b, the side surfaces of conductors 542a and 542b, the side surface of insulator 544, and the side surface of insulator 580. Oxide 530c2 is in contact with insulator 550.

[0442] As oxide 530c1, for example, In-Zn oxide can be used. Furthermore, as oxide 530c2, the same materials that can be used for oxide 530c when it has a monolayer structure can be used. For example, as oxide 530c2, metal oxides with an In:Ga:Zn ratio of 1:3:4, Ga:Zn ratio of 2:1, or Ga:Zn ratio of 2:5 can be used.

[0443] By using a two-layer structure of oxide 530c with oxide 530c1 and oxide 530c2, the on-state current of the transistor can be increased compared to a single-layer structure of oxide 530c. Therefore, the transistor can be used, for example, as a power MOS transistor. Note that... FIG. 23A and FIG. 23B The oxide 530c included in the transistor shown can also have a two-layer structure of oxide 530c1 and oxide 530c2.

[0444] Can ​ and ​ The transistors shown are used, for example, in transistor 500, transistor 300, or both transistor 500 and transistor 300.

[0445] Furthermore, this embodiment can be implemented in combination with other embodiments described in this specification.

[0446] (Implementation Method 4)

[0447] In this embodiment, the structure of the metal oxide that can be used in the OS transistor described in the above embodiments will be explained.

[0448] <Composition of Metal Oxides>

[0449] In this specification and other materials, it is sometimes referred to as CAAC (c-axis aligned crystal) or CAC (Cloud-Aligned Composite). Note that CAAC refers to an example of a crystalline structure, while CAC refers to an example of a function or material composition.

[0450] CAC-OS or CAC-metal oxide possesses conductive properties in one part of the material and insulating properties in another, thus functioning as a semiconductor as a whole. Furthermore, when CAC-OS or CAC-metal oxide is used in the channel formation region of a transistor, the conductive function allows electrons (or holes) used as charge carriers to flow through, while the insulating function prevents electrons from flowing through. Through the complementary effects of conductive and insulating functions, CAC-OS or CAC-metal oxide can possess switching functionality (controlling on / off states). By separating these functions within CAC-OS or CAC-metal oxide, each function can be maximized.

[0451] Furthermore, CAC-OS or CAC-metal oxide comprises conductive and insulating regions. The conductive regions possess the aforementioned conductive function, and the insulating regions possess the aforementioned insulating function. Moreover, in the material, the conductive and insulating regions are sometimes separated at the nanoparticle level. Additionally, the conductive and insulating regions are sometimes unevenly distributed within the material. Furthermore, conductive regions with blurred edges and cloud-like connections are sometimes observed.

[0452] Furthermore, in CAC-OS or CAC-metal oxide, conductive and insulating regions are sometimes dispersed in the material at a size of 0.5 nm or more and 10 nm or less, preferably 0.5 nm or more and 3 nm or less.

[0453] Furthermore, CAC-OS or CAC-metal oxide is composed of components with different band gaps. For example, CAC-OS or CAC-metal oxide is composed of a component with a wide gap originating from an insulating region and a component with a narrow gap originating from a conductive region. In this structure, when charge carriers flow through, they mainly flow through the component with the narrow gap. Moreover, the component with the narrow gap, through complementary interaction with the component with the wide gap, causes charge carriers to flow through the component with the wide gap. Therefore, when the above-mentioned CAC-OS or CAC-metal oxide is used in the channel formation region of a transistor, a high current driving force, i.e., a large on-state current and a high field-effect mobility, can be obtained in the transistor's on-state.

[0454] In other words, CAC-OS or CAC-metal oxide can also be referred to as matrix composite or metal matrix composite.

[0455] <Structure of Metal Oxides>

[0456] Oxide semiconductors are classified into single-crystal oxide semiconductors and non-single-crystal oxide semiconductors. Examples of non-single-crystal oxide semiconductors include CAAC-OS (c-axis aligned crystalline oxide semiconductor), polycrystalline oxide semiconductors, nc-OS (nanocrystalline oxide semiconductor), a-like OS (amorphous-like oxide semiconductor), and amorphous oxide semiconductors.

[0457] Oxide semiconductors, used as semiconductors in transistors, are preferably thin films with high crystallinity. Using such films can improve the stability or reliability of transistors. Examples of such films include, for instance, single-crystal oxide semiconductor films or polycrystalline oxide semiconductor films. However, forming single-crystal or polycrystalline oxide semiconductor films on a substrate requires high-temperature or laser heating processes. Therefore, the manufacturing process becomes more expensive and throughput decreases.

[0458] CAAC-OS exhibits c-axis orientation, with multiple nanocrystals linked along the ab-plane direction, resulting in a distorted crystal structure. Note that distortion refers to the portion of the lattice orientation that changes between regions with consistent lattice arrangement and other regions with consistent lattice arrangement within the region where multiple nanocrystals are linked.

[0459] Although nanocrystals are primarily hexagonal, they are not limited to regular hexagons and can be non-regular hexagonal. Furthermore, pentagonal or heptagonal lattice arrangements are sometimes observed in the distortion. Additionally, in CAAC-OS, no clear grain boundaries are observed even near the distortion. That is, it can be seen that the lattice arrangement distortion suppresses grain boundary formation. This may be because CAAC-OS can contain the distortion due to the low density of oxygen atoms along the ab plane or the change in interatomic bonding distance caused by the substitution of metal elements.

[0460] CAAC-OS tends to have a layered crystalline structure (also called a layered structure), in which layers containing indium and oxygen (hereinafter referred to as In layers) and layers containing elements M, zinc, and oxygen (hereinafter referred to as (M,Zn) layers) are stacked. Furthermore, indium and element M can be substituted for each other; when element M in a (M,Zn) layer is replaced by indium, the layer can also be represented as an (In,M,Zn) layer. Similarly, when indium in an In layer is replaced by element M, the layer can also be represented as an (In,M) layer.

[0461] CAAC-OS is a highly crystalline oxide semiconductor. Furthermore, no distinct grain boundaries are observed in CAAC-OS, thus reducing the likelihood of decreased electron mobility due to grain boundaries. Additionally, the crystallinity of oxide semiconductors can sometimes decrease due to the introduction of impurities or the formation of defects; therefore, CAAC-OS can be considered an oxide semiconductor with few impurities or defects (such as oxygen vacancies). Consequently, oxide semiconductors containing CAAC-OS exhibit stable physical properties. Thus, oxide semiconductors containing CAAC-OS possess high heat resistance and high reliability. Moreover, CAAC-OS is also stable against high temperatures (or thermal accumulation) during manufacturing processes. Therefore, by using CAAC-OS in OS transistors, the degrees of freedom in manufacturing processes can be increased.

[0462] In nc-OS, the atomic arrangement in tiny regions (e.g., regions above 1 nm and below 10 nm, particularly above 1 nm and below 3 nm) exhibits periodicity. Furthermore, no regularity in crystal orientation is observed between different nanocrystals in nc-OS. Therefore, no orientation is observed in the overall film. Thus, sometimes nc-OS is indistinguishable from a-like OS or amorphous oxide semiconductors in certain analytical methods.

[0463] a-like OS is an oxide semiconductor with a structure intermediate between nc-OS and amorphous oxide semiconductors. A-like OS contains voids or low-density regions. In other words, a-like OS has lower crystallinity than nc-OS and CAAC-OS.

[0464] Oxide semiconductors possess various structures and properties. One embodiment of the present invention may also include two or more of amorphous oxide semiconductors, polycrystalline oxide semiconductors, a-like OS, nc-OS, and CAAC-OS.

[0465] Transistors with oxide semiconductors

[0466] Next, we will explain the application of the aforementioned oxide semiconductor in transistors.

[0467] By using the aforementioned oxide semiconductors in transistors, transistors with high field-effect mobility can be realized. Furthermore, transistors with high reliability can also be achieved.

[0468] Oxide semiconductors with low carrier density are preferably used in transistors. When it is necessary to reduce the carrier density of an oxide semiconductor film, the impurity concentration in the oxide semiconductor film can be reduced to decrease the defect state density. In this specification and the like, the state of low impurity concentration and low defect state density is referred to as "high-purity intrinsic" or "substantially high-purity intrinsic".

[0469] Furthermore, high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor films have a lower defect state density, and therefore sometimes a lower trap state density. Note that the carrier density of the oxide semiconductor used in one embodiment of the present invention can be within the range described in Embodiment 3.

[0470] Furthermore, the charge trapped in the trap state of an oxide semiconductor takes a relatively long time to dissipate, sometimes acting like a fixed charge. Therefore, the electrical characteristics of transistors with channel formation regions formed in oxide semiconductors with high trap state density are sometimes unstable.

[0471] Therefore, reducing the impurity concentration in the oxide semiconductor is effective in stabilizing the electrical characteristics of the transistor. To further 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.

[0472] <Impurities>

[0473] Here, we will explain the effects of various impurities in oxide semiconductors.

[0474] When an oxide semiconductor contains silicon or carbon, one of Group 14 elements, defect states are formed in the oxide semiconductor. Therefore, the concentration of silicon or carbon in or near the interface of the oxide semiconductor (the concentration measured by secondary ion mass spectrometry (SIMS)) is set to 2 × 10⁻⁶. 18atoms / cm 3 The following is preferred: 2×10 17 atoms / cm 3 the following.

[0475] Furthermore, when oxide semiconductors contain alkali metals or alkaline earth metals, defect states can sometimes form, resulting in charge carriers. Therefore, transistors using oxide semiconductors containing alkali metals or alkaline earth metals tend to have always-on characteristics. Consequently, it is preferable to reduce the concentration of alkali metals or alkaline earth metals in the oxide semiconductor. Specifically, the concentration of alkali metals or alkaline earth metals in the oxide semiconductor, as measured by SIMS, should be 1 × 10⁻⁶. 18 atoms / cm 3 The following is preferred: 2×10 16 atoms / cm 3 the following.

[0476] When oxide semiconductors contain nitrogen, electrons are readily generated as charge carriers, increasing the charge carrier density and resulting in an n-type configuration. Consequently, transistors using nitrogen-containing oxide semiconductors in the channel formation region tend to exhibit always-on characteristics. Therefore, it is preferable to minimize the nitrogen content in the oxide semiconductor as much as possible. For example, the nitrogen concentration in the oxide semiconductor measured using SIMS is below 5 × 10⁻⁶. 19 atoms / cm 3 Preferably 5×10 18 atoms / cm 3 Hereinafter, 1×10 is more preferred. 18 atoms / cm 3 The following is a further preferred option: 5×10 17 atoms / cm 3 the following.

[0477] Hydrogen contained in oxide semiconductors reacts with oxygen bonded to metal atoms to form water, thus sometimes creating oxygen vacancies. When hydrogen enters these oxygen vacancies, electrons are sometimes generated as charge carriers. Additionally, sometimes a portion of the hydrogen bonds with oxygen bonded to metal atoms, generating electrons as charge carriers. Therefore, transistors using oxide semiconductors containing hydrogen tend to have always-on characteristics. Thus, it is preferable to minimize the amount of hydrogen in the oxide semiconductor. Specifically, in the oxide semiconductor, the hydrogen concentration, as measured by SIMS, is set to be less than 1 × 10⁻⁶. 20 atoms / cm 3 Preferably less than 1×10 19 atoms / cm 3 More preferably, less than 5×10 18 atoms / cm 3 Further optimization of less than 1×10 18atoms / cm 3 .

[0478] By using oxide semiconductors with sufficiently reduced impurities in the channel formation region of a transistor, the transistor can have stable electrical characteristics.

[0479] The discovery of CAAC and nc structures has contributed to improving the electrical characteristics and reliability of oxide semiconductor transistors using CAAC or nc structures, reducing manufacturing costs, and increasing throughput. Furthermore, research has been conducted on applying these transistors to semiconductor devices, leveraging their low leakage current characteristic.

[0480] Furthermore, this embodiment can be implemented in combination with other embodiments described in this specification.

[0481] [Symbol Explanation]

[0482] C11: Capacitor element, C12: Capacitor element, C21: Capacitor element, C22: Capacitor element, C41: Capacitor element, C42: Capacitor element, C43: Capacitor element, C51: Capacitor element, C52: Capacitor element, C53: Capacitor element, N11: Node, N21: Node, N41: Node, N51: Node, SI1: Signal, SI1_IN: Input terminal, SI1B: Signal, SI1B_IN: Input terminal, SI2: Signal, SI2_IN: Input terminal, SI2B: Signal, SI2B_IN: Input terminal, SO1: Signal, SO1_OUT: Output terminal, SO1B: Signal, SO2: Signal, SO2_OUT: Output terminal, SO 2B: Signal, 10: Semiconductor device, 10_1: Semiconductor device, 10_2: Semiconductor device, 11: Transistor, 12: Transistor, 13: Transistor, 14: Transistor, 20: Semiconductor device, 21: Transistor, 22: Transistor, 23: Transistor, 30: Semiconductor device, 31: Transistor, 32: Transistor, 40: Semiconductor device, 41: Transistor, 42: Transistor, 43: Transistor, 44: Transistor, 45: Transistor, 46: Transistor, 47: Transistor, 50: Semiconductor device, 51: Transistor, 52: Transistor, 53: Transistor, 54: Transistor, 55: Transistor, 56: Transistor, 57: Transistor, 60: Semiconductor device, 70: Semiconductor 300: Transistor; 311: Substrate; 313: Semiconductor region; 314a: Low-resistance region; 314b: Low-resistance region; 315: Insulator; 316: Conductor; 320: Insulator; 322: Insulator; 324: Insulator; 326: Insulator; 328: Conductor; 330: Conductor; 350: Insulator; 352: Insulator; 354: Insulator; 356: Conductor; 360: Insulator; 362: Insulator; 364: Insulator; 366: Conductor; 370: Insulator; 372: Insulator; 374: Insulator; 376: Conductor; 380: Insulator; 382: Insulator; 384: Insulator; 386: Conductor; 402: Insulator Insulator, 404: Insulator, 500: Transistor, 503: Conductor, 503a: Conductor, 503b: Conductor, 505: Conductor, 505a: Conductor, 505b: Conductor, 510: Insulator, 510A: Transistor, 510B: Transistor, 510C: Transistor, 510D: Transistor, 510E: Transistor, 510F: Transistor, 510G: Transistor, 511: Insulator, 512: Insulator, 514: Insulator, 516: Insulator, 518: Conductor, 520: Insulator, 521: Insulator, 522: Insulator, 524: Insulator, 530: Oxide, 530a: Oxide, 530b: Oxide, 530c: Oxide530c1: Oxide, 530c2: Oxide, 531: Region, 531a: Region, 531b: Region, 540a: Conductor, 540b: Conductor, 542: Conductor, 542a: Conductor, 542b: Conductor, 543: Region, 543a: Region, 543b: Region, 544: Insulator, 545: Insulator, 546: Conductor, 546a: Conductor, 546b: Conductor, 547: Conductor, 547a: Conductor, 547b: Conductor, 548: Conductor, 550: Insulator, 55 1: Insulator; 552: Metal oxide; 560: Conductor; 560a: Conductor; 560b: Conductor; 570: Insulator; 571: Insulator; 573: Insulator; 574: Insulator; 575: Insulator; 576: Insulator; 576a: Insulator; 576b: Insulator; 580: Insulator; 581: Insulator; 582: Insulator; 584: Insulator; 586: Insulator; 600: Capacitor element; 610: Conductor; 612: Conductor; 620: Conductor; 630: Insulator; 650: Insulator.

Claims

1. A semiconductor device, comprising: First to seventh transistors; First to third capacitor elements; First and second wiring; First to fourth input terminals; as well as Output terminals, In this configuration, one of the source and drain terminals of the sixth transistor is electrically connected to the first wiring. The other of the source and drain of the sixth transistor is electrically connected to one of the source and drain of the seventh transistor. The source and drain of the seventh transistor are electrically connected to one of the source and drain of the third transistor, one of the source and drain of the fourth transistor, a terminal of the third capacitor element, and the gate of the fifth transistor. The other of the source and drain of the third transistor and the other of the source and drain of the fourth transistor are electrically connected to the second wiring. The gate of the sixth transistor is electrically connected to the second input terminal, one terminal of the second capacitor element, and the gate of the first transistor. The gate of the seventh transistor is electrically connected to the first input terminal, one terminal of the first capacitor element, and the gate of the second transistor. The gate of the third transistor is electrically connected to the third input terminal. The gate of the fourth transistor is electrically connected to the fourth input terminal. One of the source and drain terminals of the first transistor is electrically connected to the first wiring. The other of the source and drain of the first transistor is electrically connected to one of the source and drain of the second transistor. The other of the source and drain of the second transistor is electrically connected to the other terminal of the first capacitor element, the other terminal of the second capacitor element, the other terminal of the third capacitor element, the source and drain of the fifth transistor, and the output terminal. The other of the source and drain of the fifth transistor is electrically connected to the second wiring. Furthermore, the first through seventh transistors are all n-channel transistors.

2. A semiconductor device, comprising: First to seventh transistors; First to third capacitor elements; First and second wiring; First to fourth input terminals; as well as Output terminals, In this configuration, one of the source and drain terminals of the sixth transistor is electrically connected to the first wiring. The other of the source and drain of the sixth transistor is electrically connected to one of the source and drain of the seventh transistor. The source and drain of the seventh transistor are electrically connected to one of the source and drain of the third transistor, one of the source and drain of the fourth transistor, a terminal of the third capacitor element, and the gate of the fifth transistor. The other of the source and drain of the third transistor and the other of the source and drain of the fourth transistor are electrically connected to the second wiring. The gate of the sixth transistor is electrically connected to the second input terminal, one terminal of the second capacitor element, and the gate of the first transistor. The gate of the seventh transistor is electrically connected to the first input terminal, one terminal of the first capacitor element, and the gate of the second transistor. The gate of the third transistor is electrically connected to the third input terminal. The gate of the fourth transistor is electrically connected to the fourth input terminal. One of the source and drain terminals of the first transistor is electrically connected to the first wiring. The other of the source and drain of the first transistor is electrically connected to one of the source and drain of the second transistor. The other of the source and drain of the second transistor is electrically connected to the other terminal of the first capacitor element, the other terminal of the second capacitor element, the other terminal of the third capacitor element, the source and drain of the fifth transistor, and the output terminal. The other of the source and drain of the fifth transistor is electrically connected to the second wiring. Furthermore, the semiconductor device has the functionality of a NAND circuit.

3. The semiconductor device according to claim 2, The first to seventh transistors are n-channel transistors.

4. A semiconductor device, comprising: First to seventh transistors; First to third capacitor elements; First and second wiring; First to fourth input terminals; as well as Output terminals, In this configuration, one of the source and drain terminals of the sixth transistor is electrically connected to the first wiring. The other of the source and drain of the sixth transistor is electrically connected to one of the source and drain of the seventh transistor. The other of the source and drain terminals of the seventh transistor is electrically connected to one of the source and drain terminals of the third transistor, one of the source and drain terminals of the fourth transistor, a terminal of the third capacitor element, and the gate of the fifth transistor. The other of the source and drain of the third transistor and the other of the source and drain of the fourth transistor are electrically connected to the second wiring. The gate of the sixth transistor is electrically connected to the second input terminal, one terminal of the second capacitor element, and the gate of the first transistor. The gate of the seventh transistor is electrically connected to the first input terminal, one terminal of the first capacitor element, and the gate of the second transistor. The gate of the third transistor is electrically connected to the third input terminal. The gate of the fourth transistor is electrically connected to the fourth input terminal. One of the source and drain terminals of the first transistor is electrically connected to the first wiring. The other of the source and drain of the first transistor is electrically connected to one of the source and drain of the second transistor. The other of the source and drain of the second transistor is electrically connected to the other terminal of the first capacitor element, the other terminal of the second capacitor element, the other terminal of the third capacitor element, the source and drain of the fifth transistor, and the output terminal. Furthermore, the other of the source and drain of the fifth transistor is electrically connected to the second wiring.

5. The semiconductor device according to any one of claims 1, 2, and 4, The first wiring is supplied with a first potential. The second wiring is supplied with a second potential. The second potential is a higher potential than the first potential. The first signal is input to the first input terminal. The second signal is input to the second input terminal. The third signal is input to the third input terminal. A fourth signal is input to the fourth input terminal. The third signal is a signal obtained by logically inverting the first signal. Furthermore, the fourth signal is a signal obtained by logically inverting the second signal.

6. The semiconductor device according to any one of claims 1, 2, and 4, The first to seventh transistors contain metal oxides in the channel formation region.

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