Display device

Abstract

To provide a display device with high luminance.SOLUTION: A pixel includes a light-emitting device, a first transistor, a second transistor, a third transistor, a fourth transistor, a first capacitor element, and a second capacitor element. One electrode of the light-emitting device is electrically connected to one of the source and the drain of the first transistor. The gate of the first transistor is electrically connected to one electrode of the first capacitor element and one of the source and the drain of the second transistor. The other of the source and the drain of the first transistor is electrically connected to one electrode of the second capacitor element. The one electrode of the second capacitor element is electrically connected to a first wire with a function of supplying a first potential. The other electrode of the second capacitor element is electrically connected to the other electrode of the first capacitor element, one of the source and the drain of the third transistor, and one of the source and the drain of the fourth transistor.SELECTED DRAWING: Figure 1

Description

Technical Field

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

[0002] Note that one aspect of the present invention is not limited to the above technical field. Examples of the technical field of one aspect of the present invention disclosed in this specification and the like include semiconductor devices, display devices, light-emitting devices, power storage devices, storage devices, electronic devices, lighting devices, input devices, input / output devices, their driving methods, or their manufacturing methods. A semiconductor device refers to all devices that can function by utilizing semiconductor characteristics.

Background Art

[0003] As a semiconductor material applicable to a transistor, an oxide semiconductor using a metal oxide has attracted attention. For example, in Patent Document 1, a semiconductor device in which a plurality of oxide semiconductor layers are stacked, and among the plurality of oxide semiconductor layers, the oxide semiconductor layer serving as a channel contains indium and gallium, and the ratio of indium is made larger than the ratio of gallium, thereby increasing the field-effect mobility (sometimes simply referred to as mobility, μFE, or μ) is disclosed.

[0004] Since the metal oxide that can be used for the semiconductor layer can be formed by a sputtering method or the like, it can be used for the transistors constituting a large-sized display device. In addition, since a part of the production equipment for transistors using polycrystalline silicon or amorphous silicon can be improved and utilized, equipment investment can be suppressed. Further, since a transistor using a metal oxide has a higher field-effect mobility than when amorphous silicon is used, a high-functional display device provided with a driving circuit can be realized.

[0005] By the way, as display devices for augmented reality (AR) or virtual reality (VR), wearable display devices and stationary display devices are becoming increasingly popular. Examples of wearable display devices include head-mounted displays (HMDs) and glasses-type display devices. Examples of stationary display devices include head-up displays (HUDs).

[0006] In an electronic device having an imaging device such as a digital camera, a viewfinder is used to confirm the image to be captured before imaging. Also, an electronic viewfinder is used as the viewfinder. The electronic viewfinder is provided with a display unit, and an image obtained by the imaging device can be displayed as an image on the display unit. For example, Patent Document 2 discloses an electronic viewfinder capable of obtaining a good visibility state from the central part to the peripheral part of the image.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] In display devices such as HMDs where the distance between the display unit and the user is short, since the user can easily visually recognize the pixels and strongly feel the granularity, the immersion and presence of AR and VR may be reduced. For this reason, in an HMD, a high-definition display device that has fine pixels so that the user does not visually recognize the pixels is desired. The pixel density of the display device is preferably, for example, 1000 ppi or more, more preferably 5000 ppi or more, and even more preferably 7000 ppi or more. Further, in the case of AR applications, since the image in the virtual space is overlaid and displayed in the real space, a display device with high brightness is particularly desired when the usage environment is bright.

[0009] In view of the above, one aspect of the present invention aims to provide a display device with high definition. Or, one aspect of the present invention aims to provide a display device with high brightness. Or, one aspect of the present invention aims to provide a display device with low power consumption. Or, one aspect of the present invention aims to provide a display device with a narrow bezel. Or, one aspect of the present invention aims to provide a small display device. Or, one aspect of the present invention aims to provide a novel display device.

[0010] Note that the description of these problems does not prevent the existence of other problems. Note that one aspect of the present invention does not need to solve all of these problems. Note that other problems can be extracted from the descriptions in the specification, drawings, claims, etc.

Means for Solving the Problems

[0011] One aspect of the present invention is a display device having a pixel portion having a plurality of pixels, a first wiring, a second wiring, a third wiring, and a fourth wiring. Each pixel has a light-emitting device, a first transistor, a second transistor, a third transistor, a fourth transistor, a first capacitive element, and a second capacitive element. One electrode of the light-emitting device is electrically connected to one of the source or drain of the first transistor. The gate of the first transistor is electrically connected to one electrode of the first capacitive element and one of the source or drain of the second transistor. The other of the source or drain of the first transistor is electrically connected to one electrode of the second capacitive element. One electrode of the second capacitive element is electrically connected to the first wiring having a function of supplying a first potential. The other electrode of the second capacitive element is electrically connected to the other electrode of the first capacitive element, one of the source or drain of the third transistor, and one of the source or drain of the fourth transistor. The gates of the second transistor and the fourth transistor are each electrically connected to the second wiring. The gate of the third transistor is electrically connected to the third wiring. The other of the source or drain of the second transistor and the other of the source or drain of the third transistor are each electrically connected to the fourth wiring.

[0012] In the above-described display device, it is preferable that the first transistor has a back gate, and the back gate is electrically connected to one of the source or drain of the first transistor.

[0013] In the above-described display device, it is preferable that the first transistor has a back gate, and the back gate is electrically connected to the gate of the first transistor.

[0014] In the above-described display device, it further preferably has a fifth transistor, and one of the source or drain of the fifth transistor is electrically connected to one electrode of the light-emitting device.

[0015] In the aforementioned display device, the other electrode of the light-emitting device is electrically connected to a fifth wiring having a function of supplying a second potential, and the second potential is preferably lower than the first potential.

[0016] In the aforementioned display device, the light-emitting device is preferably an organic light-emitting diode.

[0017] In the aforementioned display device, it preferably has a first drive circuit section, and the first drive circuit section preferably has a region overlapping with the pixel section. The first drive circuit section is preferably electrically connected to the fourth wiring.

[0018] In the aforementioned display device, it preferably has a first layer and a second layer on the first layer. The first layer preferably has a first drive circuit section and a second drive circuit section. The second layer preferably has a pixel section. The second drive circuit section is preferably electrically connected to the second wiring and the third wiring.

[0019] In the aforementioned display device, the first transistor, the second transistor, the third transistor, and the fourth transistor preferably each have a metal oxide in a channel formation region. The metal oxide preferably has indium, zinc, and one or more of elements M (aluminum, titanium, gallium, germanium, yttrium, zirconium, lanthanum, cerium, tin, neodymium, or hafnium).

[0020] One aspect of the present invention is an electronic device having the aforementioned display device and a camera.

Effects of the Invention

[0021] According to one aspect of the present invention, a display device with high definition can be provided. Or, according to one aspect of the present invention, a display device with high brightness can be provided. Or, according to one aspect of the present invention, a display device with low power consumption can be provided. Or, according to one aspect of the present invention, a display device with a narrow frame can be provided. Or, according to one aspect of the present invention, a small-sized display device can be provided. Or, according to one aspect of the present invention, a novel display device can be provided.

[0022] Note that the description of these effects does not prevent the existence of other effects. Note that one aspect of the present invention does not necessarily have to have all of these effects. Note that other effects can be extracted from the descriptions in the specification, drawings, claims, etc.

Brief Description of the Drawings

[0023]

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DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments will be described with reference to the drawings. However, it should be easily understood by those skilled in the art that the embodiments can be implemented in many different ways, and the forms and details can be variously changed without departing from the spirit and scope thereof. Therefore, the present invention is not to be construed as being limited to the description of the following embodiments.

[0025] In each of the figures described in this specification, the size of each component, the thickness of each layer, or the area may be exaggerated for clarity.

[0026] The ordinal numbers "first", "second", "third", etc. used in this specification and the like are attached to avoid confusion of components and are not numerically limiting.

[0027] In this specification and the like, terms indicating arrangements such as "above" and "below" are used for convenience in explaining the positional relationship between components with reference to the drawings. Also, the positional relationship between components appropriately changes according to the direction in which each component is depicted. Therefore, it is not limited to the terms described in the specification and can be appropriately rephrased according to the situation.

[0028] In this specification and the like, the functions of the source and drain of a transistor may be interchanged when the polarity of the transistor or the direction of the current changes in the circuit operation. For this reason, the terms source and drain can be used interchangeably.

[0029] In this specification and the like, terms such as "electrode", "wiring", and "terminal" do not functionally limit these components. For example, an "electrode" may be used as part of "wiring", and vice versa. Furthermore, the terms "electrode" and "wiring" also include cases where a plurality of "electrodes" and "wirings" are integrally formed. Also, for example, a "terminal" may be used as part of "wiring" or "electrode", and vice versa. Furthermore, the term "terminal" also includes cases where a plurality of "electrodes", "wirings", "terminals", etc. are integrally formed. Therefore, for example, an "electrode" can be part of "wiring" or "terminal", and for example, a "terminal" can be part of "wiring" or "electrode". Also, the terms such as "electrode", "wiring", and "terminal" may, in some cases, be replaced with terms such as "region".

[0030] In this specification and the like, "resistance" may be determined by the length of the wiring. Or, resistance also includes cases where it is formed by connecting, via a contact, a conductor having a lower efficiency different from the conductor used in the wiring. Or, the resistance value may be determined by doping impurities into a semiconductor.

[0031] In this specification and the like, "electrically connected" includes cases where it is directly connected and cases where it is connected via "something having some electrical effect". Here, "something having some electrical effect" is not particularly limited as long as it enables the transfer of electrical signals between the connection targets. Therefore, even when expressed as "electrically connect", in an actual circuit, there may be a case where there is no physical connection part and only the wiring extends. Also, even when expressed as "directly connected", it includes cases where the wiring is formed via a contact on different conductors. Note that for the wiring, there are cases where different conductors contain one or more of the same elements and cases where they contain different elements.

[0032] In this specification and the like, the term "film" and the term "layer" can be mutually interchanged. For example, the terms "conductive layer" and "insulating layer" may be mutually interchangeable with the terms "conductive film" and "insulating film" in some cases.

[0033] In this specification and the like, unless otherwise specified, the off-current refers to the drain current when the transistor is in the off state (also referred to as the non-conductive state or the cut-off state). The off state, unless otherwise specified, for an n-channel type transistor, is a state where the voltage V gs between the gate and the source is lower than the threshold voltage V th (for a p-channel type transistor, higher than V th ).

[0034] In the drawings, the size, layer thickness, or area may be exaggerated for clarity. Therefore, it is not necessarily limited to that scale. Note that the drawings are shown schematically and are not limited to the shapes or values shown in the drawings. For example, in an actual manufacturing process, layers, resist masks, etc. may be unintentionally thinned due to processes such as etching, but this may not be reflected in the drawings for ease of understanding. Also, in the drawings, the same reference numerals are commonly used for the same part or parts having the same function, material, etc. among different drawings, and the repeated description may be omitted. Also, when referring to parts having the same function, material, etc., the hatch pattern may be the same and may not be particularly labeled.

[0035] In this specification and the like, metal oxide means an oxide of a metal in a broad sense. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), oxide semiconductors (also referred to as Oxide Semiconductor or simply OS), etc. For example, when a metal oxide is used for the active layer of a transistor, the metal oxide may be referred to as an oxide semiconductor. That is, when described as an OS transistor, it can be paraphrased as a transistor having an oxide or an oxide semiconductor.

[0036] (Embodiment 1) In this embodiment, a display device which is an aspect of the present invention will be described.

[0037] One aspect of the present invention is a display device having pixels. Each pixel has a function of generating a voltage higher than the voltage corresponding to the image data supplied from a source driver. A storage node is provided for each pixel, and first data can be held in the storage node. Further, second data is supplied to each pixel, and the first data is added to the second data by capacitive coupling. Then, the data obtained by adding the first data to the second data can be supplied to a light-emitting device. Alternatively, after writing the second data into the storage node, the first data can be added by capacitive coupling.

[0038] The same image data can be used as the first data and the second data. In this case, the pixels of the display device can generate a voltage higher than the voltage corresponding to the image data supplied from the source driver and supply the voltage to a driving transistor that controls the amount of current flowing through the light-emitting device. Therefore, the current flowing through the light-emitting device can be increased, and a display device with high brightness can be obtained.

[0039] For example, a display device which is an aspect of the present invention can be suitably used as a display device for AR that requires high brightness. Also, the output voltage of the source driver can be reduced, and a display device with low power consumption can be obtained. Further, a high-voltage output driver can be made unnecessary, and a general-purpose driver IC or the like can be used. Alternatively, a light-emitting device that is difficult to operate even when using a high-voltage output driver can also be operated.

[0040] Note that in this specification and the like, generating a voltage higher than the supplied voltage may be referred to as boosting.

[0041] A display device according to one aspect of the present invention can use, for example, image data as the first data and correction data as the second data. In this case, the display device can display a corrected image. By this correction, up-conversion of the image can be performed. Alternatively, a part or all of the image in the display area can be corrected to perform HDR (High Dynamic Range) display.

[0042] A display device according to one aspect of the present invention can display arbitrary images superimposed by using, for example, different image data as the first data and the second data.

[0043] A display device according to one aspect of the present invention has a pixel portion having a plurality of pixels and an area where the source driver overlaps. By having an area where the pixel portion and the source driver overlap, the area of the frame, which is an area where no pixel is provided, can be reduced. Therefore, a display device with a narrow frame can be obtained. Further, by narrowing the frame of the display device, a small display device can be obtained.

[0044] In this specification and the like, a pixel refers to, for example, one element that can control brightness. Therefore, as an example, one pixel refers to one color element, and the brightness is expressed by one such color element. Therefore, in the case of a color display device composed of color elements of R (red), G (green), and B (blue), the minimum unit of the image is assumed to be composed of three pixels: an R pixel, a G pixel, and a B pixel. In this case, each of the RGB pixels is called a sub-pixel, and the RGB sub-pixels may be collectively called a pixel.

[0045] <Configuration Example 1 of Pixel> A configuration example of pixel 10 that can be used in a display device according to one aspect of the present invention is shown in FIG. 1. Pixel 10 has a light-emitting device 114, a transistor 101, a transistor 102, a transistor 103, a transistor 104, a capacitive element 111, and a capacitive element 112.

[0046] One electrode of the light-emitting device 114 is electrically connected to one of the source or drain of the transistor 101. The gate of the transistor 101 is electrically connected to one electrode of the capacitor element 111. The gate of the transistor 101 is electrically connected to one of the source or drain of the transistor 102. The other of the source or drain of the transistor 101 is electrically connected to one electrode of the capacitor element 112. The other electrode of the capacitor element 112 is electrically connected to the other electrode of the capacitor element 111. The other electrode of the capacitor element 112 is electrically connected to one of the source or drain of the transistor 103. The other electrode of the capacitor element 112 is electrically connected to one of the source or drain of the transistor 104.

[0047] In the pixel 10 shown in FIG. 1, the capacitor element 111 and the capacitor element 112 are connected in series, and through these capacitor elements, the gate of the transistor 101 that functions as a driving transistor and the other of the source or drain are electrically connected.

[0048] Examples of the light-emitting device 114 include self-luminous light-emitting devices such as a light-emitting diode (LED), an organic light-emitting diode (OLED), a light-emitting diode using quantum dots in a light-emitting layer (QLED), and a semiconductor laser. Also, an MEMS (Micro Electro Mechanical Systems) element of a shutter method or an optical interference method, an element applying a microcapsule method, an electrophoresis method, an electro-wetting method, or an electrowetting (registered trademark) method, etc. can also be used.

[0049] Here, a wiring to which one of the gate of the transistor 101, one of the source or drain of the transistor 102, and one electrode of the capacitor element 111 are connected is defined as a node ND1. The potential of the node ND1 can control the current flowing through the light-emitting device 114, and thus control the emission luminance of the light-emitting device 114. A wiring to which one of the source or drain of the transistor 103, one of the source or drain of the transistor 104, the other electrode of the capacitor element 111, and the other electrode of the capacitor element 112 are connected is defined as a node ND2.

[0050] The transistor 101 functions as a driving transistor that controls the amount of current flowing through the light-emitting device 114. The transistors 102 and 103 function as selection transistors that select a pixel. The transistor 104 functions as a switch for writing a specific potential (reference potential) “Vref” for driving the pixel 10 to the pixel.

[0051] The gate of the transistor 102 is electrically connected to the wiring 121. The gate of the transistor 104 is electrically connected to the wiring 121. The gate of the transistor 103 is electrically connected to the wiring 122. The other of the source or drain of the transistor 102 is electrically connected to the wiring 131. The other of the source or drain of the transistor 103 is electrically connected to the wiring 131.

[0052] One electrode of the capacitive element 112 is electrically connected to the wiring 128. The wiring 128 preferably has a function of supplying a specific potential. By electrically connecting one electrode of the capacitive element 112 to the wiring 128, the potential of one electrode of the capacitive element 112 can be fixed to the specific potential supplied from the wiring 128, and the boosting operation can be stably performed. Further, the other electrode of the light-emitting device 114 is electrically connected to the wiring 129. The wirings 128 and 129 can each function as a wiring (power supply line) to which a power supply potential is applied. For example, the wiring 128 can function as a high-potential power supply line that supplies a potential higher than that of the wiring 129. Also, the wiring 129 can function as a low-potential power supply line that supplies a potential lower than that of the wiring 128.

[0053] The wirings 121 and 122 have a function as scanning lines for controlling the operations of the transistors 102, 103, and 104. The scanning signal applied to the scanning line is a signal for controlling the conduction state or non-conduction state (on or off) of the selection transistors (transistors 102, 103, and 104) that function as switches in the pixel 10. The wiring 131 has a function as a data line for supplying the first data and the second data. The wiring 127 has a function of supplying a specific potential (reference potential) “Vref” for driving the pixel 10.

[0054] The node ND1 is a storage node, and by turning on the transistor 102, the first data supplied to the wiring 131 can be written into the node ND1. By turning off the transistor 102, the first data written into the node ND1 can be held.

[0055] Node ND2 is a memory node. By turning on transistor 103, the second data supplied to wiring 131 can be written into node ND2. By turning on transistor 104, the second data supplied to wiring 127 can be written into node ND2. Also, by turning off transistors 103 and 104, the second data written into node ND2 can be retained.

[0056] It is preferable to use at least one of transistors 101, 102, 103, and 104 that has an extremely small off-current. In particular, by using transistors with extremely small off-currents for transistors 102, 103, and 104, it becomes possible to hold the potentials of nodes ND1 and ND2 for a long time. For such transistors, for example, a transistor using a metal oxide in the channel formation region (hereinafter referred to as an OS transistor) can be preferably used.

[0057] Note that it is more preferable to apply OS transistors to all of transistors 101, 102, 103, and 104. Also, an OS transistor may be applied to transistors other than transistors 101, 102, 103, and 104 (not shown). Also, when operating within an acceptable range of leakage current, a transistor having silicon in the channel formation region (hereinafter referred to as an Si transistor) may be applied. Alternatively, an OS transistor and an Si transistor may be used in combination. Note that examples of the Si transistor include a transistor having amorphous silicon, a transistor having crystalline silicon (microcrystalline silicon, low-temperature polysilicon, single-crystalline silicon), and the like. Note that all of the transistors shown in FIG. 1 are n-channel type transistors, but p-channel type transistors can also be used.

[0058] As a semiconductor material used for an OS transistor, a metal oxide having an energy gap of 2 eV or more, preferably 2.2 eV or more, more preferably 2.5 eV or more can be used. Typically, it is an oxide semiconductor containing indium, etc. For example, CAAC-OS (C-Axis Aligned Crystalline Oxide Semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor) described later can be used. CAAC-OS has a stable crystal structure and is suitable for transistors that emphasize reliability. In addition, since CAC-OS exhibits high mobility characteristics, it is suitable for transistors that perform high-speed driving.

[0059] Since the OS transistor has a large energy gap in the semiconductor layer, it can exhibit an extremely small off-current characteristic of several yA / μm (y is 10 -24 ) per 1 μm of channel width. In addition, the OS transistor has characteristics different from those of Si transistors, such as no occurrence of impact ionization, avalanche breakdown, and short-channel effect, and a highly reliable circuit can be formed. Also, variations in electrical characteristics due to non-uniform crystallinity, which are problems in Si transistors, are less likely to occur in OS transistors.

[0060] The semiconductor layer included in the OS transistor can be a film represented by an In-M-Zn-based oxide containing, for example, indium, zinc, and element M (M is one or more of aluminum, titanium, gallium, germanium, yttrium, zirconium, lanthanum, cerium, tin, neodymium, or hafnium).

[0061] When the oxide semiconductor constituting the semiconductor layer is an In-M-Zn-based oxide, the atomic ratio of the metal elements of the sputtering target used to form the In-M-Zn oxide preferably satisfies In≥M and Zn≥M. As the atomic ratio of the metal elements of such a sputtering target, In:M:Zn = 1:1:1, In:M:Zn = 1:1:1.2, In:M:Zn = 3:1:2, In:M:Zn = 4:2:3, In:M:Zn = 4:2:4.1, In:M:Zn = 5:1:3, In:M:Zn = 5:1:6, In:M:Zn = 5:1:7, In:M:Zn = 5:1:8, In:M:Zn = 10:1:3, In:M:Zn = 10:1:6, In:M:Zn = 10:1:8, etc. are preferable. Note that the atomic ratio of the semiconductor layer formed includes fluctuations of plus or minus 40% of the atomic ratio of the metal elements contained in the above sputtering target, respectively.

[0062] As the semiconductor layer, an oxide semiconductor with a low carrier concentration is used. For example, the semiconductor layer has a carrier concentration of 1×10 17 / cm 3 or less, preferably 1×10 15 / cm 3 or less, more preferably 1×10 13 / cm 3 or less, even more preferably 1×10 11 / cm 3 or less, still more preferably 1×10 10 / cm 3 less, and an oxide semiconductor with a carrier concentration of 1×10 -9 / cm 3 or more can be used. Such an oxide semiconductor is called a high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor. It can be said that the oxide semiconductor has a low defect level density and stable characteristics.

[0063] In addition, without being limited to these, those having an appropriate composition may be used according to the semiconductor characteristics and electrical characteristics (such as field-effect mobility and threshold voltage) of the required transistors. Further, in order to obtain the semiconductor characteristics of the required transistors, it is preferable to make the carrier concentration, impurity concentration, defect density, atomic number ratio of metal elements and oxygen, interatomic distance, density, etc. of the semiconductor layer appropriate.

[0064] In an oxide semiconductor constituting a semiconductor layer, when silicon or carbon, which is one of the Group 14 elements, is contained, oxygen deficiency increases and it becomes n-type. For this reason, the concentration of silicon or carbon (concentration obtained by secondary ion mass spectrometry) in the semiconductor layer is set to 2×10 18 atoms / cm 3 or less, preferably 2×10 17 atoms / cm 3 or less.

[0065] When an alkali metal and an alkaline earth metal are combined with a component contained in an oxide semiconductor, carriers may be generated, and the off-current of the transistor may increase. For this reason, the concentration of the alkali metal or alkaline earth metal (concentration obtained by secondary ion mass spectrometry) in the semiconductor layer is set to 1×10 18 atoms / cm 3 or less, preferably 2×10 16 atoms / cm 3 or less.

[0066] When nitrogen is contained in the oxide semiconductor constituting the semiconductor layer, electrons serving as carriers are generated in the oxide semiconductor, the carrier concentration increases, and it tends to become n-type. As a result, a transistor using an oxide semiconductor containing nitrogen tends to have normally-on characteristics. For this reason, the nitrogen concentration (concentration obtained by secondary ion mass spectrometry) in the semiconductor layer is preferably set to 5×10 18 atoms / cm 3 or less.

[0067] When hydrogen is contained in the oxide semiconductor that constitutes the semiconductor layer, it reacts with oxygen that binds to metal atoms contained in the oxide semiconductor to become water, so oxygen vacancies may be formed in the oxide semiconductor. When oxygen vacancies are contained in the channel formation region in the oxide semiconductor, the transistor may have normally-on characteristics. Further, defects in which hydrogen enters the oxygen vacancies may function as donors, and electrons that are carriers may be generated. Also, a part of hydrogen may bind to oxygen that binds to metal atoms to generate electrons that are carriers. Therefore, a transistor using an oxide semiconductor containing a large amount of hydrogen tends to have normally-on characteristics.

[0068] Defects in which hydrogen enters the oxygen vacancies can function as donors of the oxide semiconductor. However, it is difficult to quantitatively evaluate the defects. Therefore, in the oxide semiconductor, it may be evaluated by the carrier concentration instead of the donor concentration. Thus, in this specification and the like, as a parameter of the oxide semiconductor, the carrier concentration assuming a state where no electric field is applied may be used instead of the donor concentration. That is, the "carrier concentration" described in this specification and the like may be able to be paraphrased as the "donor concentration".

[0069] Therefore, it is preferable that hydrogen in the oxide semiconductor is reduced as much as possible. Specifically, in the oxide semiconductor, the hydrogen concentration obtained by secondary ion mass spectrometry (SIMS) is less than 1×10 20 atoms / cm 3 , preferably less than 1×10 19 atoms / cm 3 , more preferably less than 5×10 18 atoms / cm 3 , still more preferably less than 1×10 18 atoms / cm 3 . By using an oxide semiconductor in which impurities such as hydrogen are sufficiently reduced in the channel formation region of the transistor, stable electrical characteristics can be imparted.

[0070] Oxide semiconductors (metal oxides) are classified into single-crystalline oxide semiconductors and other non-single-crystalline oxide semiconductors. Non-single-crystalline oxide semiconductors include, for example, CAAC-OS, polycrystalline oxide semiconductors, nc-OS (nanocrystalline oxide semiconductor), pseudo-amorphous oxide semiconductors (a-like OS: amorphous-like oxide semiconductor), and amorphous oxide semiconductors. In a non-single-crystalline structure, the amorphous structure has the highest density of defect levels, and CAAC-OS has the lowest density of defect levels.

[0071] An oxide semiconductor film with an amorphous structure has, for example, a disordered atomic arrangement and no crystalline component. Or, an oxide semiconductor film with an amorphous structure has, for example, a complete amorphous structure and no crystalline part.

[0072] Note that the semiconductor layer may be a mixed film having two or more of an amorphous structure region, a microcrystalline structure region, a polycrystalline structure region, a CAAC-OS region, and a single-crystalline structure region. The mixed film may have, for example, a single-layer structure or a laminated structure including any two or more of the above-described regions.

[0073] Hereinafter, the configuration of CAC-OS, which is one aspect of the non-single-crystalline semiconductor layer, will be described.

[0074] CAC-OS is, for example, a configuration of a material in which the elements constituting the oxide semiconductor are unevenly distributed in a size of 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 2 nm or less, or in the vicinity thereof. Hereinafter, in the oxide semiconductor, a state in which one or more metal elements are unevenly distributed and the regions having the metal elements are mixed in a size of 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 2 nm or less, or in the vicinity thereof is also referred to as a mosaic state or a patch state.

[0075] Note that the oxide semiconductor preferably contains at least indium. In particular, it preferably contains indium and zinc. In addition to these, one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or magnesium may be contained.

[0076] For example, in the In-Ga-Zn oxide, CAC-OS (among CAC-OS, the In-Ga-Zn oxide may be particularly referred to as CAC-IGZO.) refers to indium oxide (hereinafter, InO X1 (where X1 is a real number greater than 0).), or indium zinc oxide (hereinafter, In X2 Zn Y2 O Z2 (where X2, Y2, and Z2 are real numbers greater than 0).), and gallium oxide (hereinafter, GaO X3 (where X3 is a real number greater than 0).), or gallium zinc oxide (hereinafter, Ga X4 Zn Y4 O Z4 (where X4, Y4, and Z4 are real numbers greater than 0).) and other materials are separated to form a mosaic shape, and the mosaic-shaped InO X1 , or In X2 Zn Y2 O Z2 is uniformly distributed in the film (hereinafter, also referred to as a cloud-like state).

[0077] That is, CAC-OS is a composite oxide semiconductor having a structure in which a region mainly composed of GaO X3 and a region mainly composed of In X2 Zn Y2 O Z2 , or InO X1 are mixed. In this specification, for example, when the atomic ratio of In to the element M in the first region is greater than the atomic ratio of In to the element M in the second region, it is said that the first region has a higher In concentration compared to the second region.

[0078] Note that IGZO is a common name and may refer to a single compound of In, Ga, Zn, and O. As a representative example, InGaO3(ZnO) m1 (m1 is a natural number), or In (1+x0) Ga (1-x0) O3(ZnO) m0 (-1 ≤ x0 ≤ 1, m0 is an arbitrary number). Examples of crystalline compounds represented by this formula include those having a single crystal structure, a polycrystalline structure, or a CAAC structure. The CAAC structure is a crystal structure in which a plurality of IGZO nanocrystals have c-axis orientation and are connected without orientation in the a-b plane.

[0079] The above crystalline compound has a single crystal structure, a polycrystalline structure, or a CAAC structure. Note that the CAAC structure is a crystal structure in which a plurality of IGZO nanocrystals have c-axis orientation and are connected without orientation in the a-b plane.

[0080] On the other hand, CAC-OS relates to the material composition of an oxide semiconductor. CAC-OS refers to a structure in which regions observed as nanoparticle-like regions mainly composed of Ga and regions observed as nanoparticle-like regions mainly composed of In are randomly dispersed in a mosaic pattern in a material composition containing In, Ga, Zn, and O. Therefore, in CAC-OS, the crystal structure is a secondary element.

[0081] Note that CAC-OS does not include a laminated structure of two or more films having different compositions. For example, a structure composed of two layers, a film mainly composed of In and a film mainly composed of Ga, is not included.

[0082] Note that GaO X3 in the region where it is the main component and In X2 Zn Y2 O Z2 , or InO X1 in the region where it is the main component may not have a clear boundary.

[0083] In addition, when one or more selected from aluminum, yttrium, copper, vanadium, beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or magnesium are included instead of gallium, CAC-OS refers to a structure in which regions observed as nanoparticles mainly composed of the metal element and regions observed as nanoparticles mainly composed of In are randomly dispersed in a mosaic pattern, respectively.

[0084] CAC-OS can be formed by a sputtering method, for example, under conditions where the substrate is not heated. Also, when forming CAC-OS by the sputtering method, any one or more selected from inert gases (typically argon), oxygen gas, and nitrogen gas can be used as the film-forming gas. Further, the lower the flow rate ratio of oxygen gas to the total flow rate of the film-forming gas during film formation, the more preferable it is. For example, it is preferable that the flow rate ratio of oxygen gas is 0% or more and less than 30%, preferably 0% or more and 10% or less.

[0085] CAC-OS has the characteristic that no distinct peak is observed when measured using θ / 2θ scan by the Out-of-plane method, which is one of the X-ray diffraction (XRD) measurement methods. That is, it can be seen from the X-ray diffraction measurement that there is no orientation in the a-b plane direction and the c-axis direction of the measurement region.

[0086] In the electron diffraction pattern obtained by irradiating an electron beam with a probe diameter of 1 nm (also referred to as a nano-beam electron beam), a region with high luminance in a ring shape (ring region) and a plurality of bright spots are observed in the ring region. Therefore, it can be seen from the electron diffraction pattern that the crystal structure of CAC-OS has an nc (nano-crystal) structure without orientation in the plane direction and the cross-sectional direction.

[0087] For example, in CAC-OS in In-Ga-Zn oxide, regions where GaO X3 is the main component and regions where In X2 Zn Y2 O Z2 , or InO X1 is the main component are unevenly distributed and mixed, and it can be confirmed that they have a structure.

[0088] CAC-OS has a structure different from that of an IGZO compound in which metal elements are uniformly distributed and has properties different from those of an IGZO compound. That is, CAC-OS has a structure in which regions where components such as GaO X3 are the main component and regions where In X2 Zn Y2 O Z2 , or InO X1 is the main component are phase-separated from each other, and regions with each element as the main component have a mosaic-like structure.

[0089] Here, regions where In X2 Zn Y2 O Z2 , or InO X1 is the main component are regions with higher conductivity compared to regions where components such as GaO X3 are the main component. That is, when carriers flow through regions where In X2 Zn Y2 O Z2 , or InO X1 is the main component, conductivity as an oxide semiconductor is exhibited. Therefore, when regions where In X2 Zn Y2 O Z2 , or InO X1 is the main component are distributed in a cloud-like manner in the oxide semiconductor, high field-effect mobility (μ) can be realized.

[0090] On the other hand, regions where components such as GaO X3 are the main component are In X2 Zn Y2 O Z2 , or InOX1 is a region with higher insulation compared to the region where it is the main component. That is, GaO X3 and the like being the main component are distributed in the oxide semiconductor, suppressing the leakage current and enabling a good switching operation.

[0091] Therefore, when CAC-OS is used in a semiconductor device, the insulation due to GaO X3 and the like, and the conductivity due to In X2 Zn Y2 O Z2 or InO X1 act complementarily to achieve a high on-current (I on ) and a high field-effect mobility (μ).

[0092] The semiconductor device using CAC-OS has high reliability. Therefore, CAC-OS is suitable as a constituent material for various semiconductor devices.

[0093] <Example of Pixel Operation 1> Using the timing chart shown in FIG. 2, an example of the boosting operation of pixel 10 will be described. Here, the same image data is used as the first data and the second data, and by adding the second data to the first data, an example of an operation of generating a voltage higher than the voltage corresponding to the image data is shown.

[0094] In the following description, a high potential is represented as "High" and a low potential as "Low". Also, the image data is "Vdata" and a specific potential is "Vref". "Vref" can use, for example, 0V, the GND potential, or a specific reference potential. Also, the potential of wiring 128 is "Vano". "Vano" is preferably set to the potential at which transistor 101 operates in the saturation region when the luminance of light-emitting device 114 is maximum. Also, the potential of wiring 129 is "Vcath". "Vcath" is preferably set to the potential at which light-emitting device 114 does not emit light when the potential of node ND1 is the lowest potential.

[0095] First, the operation of writing image data "Vdata" as the first data to node ND1 will be described. Here, in terms of potential distribution, connection, or loss, detailed changes due to circuit configuration, operation timing, etc. are not considered.

[0096] At time T1, when the potential of wiring 121 is "High", the potential of wiring 122 is "Low", the potential of wiring 131 is "Vdata", and the potential of wiring 127 is "Vref", transistors 102 and 104 become conductive, and the potential "Vdata" of wiring 131 is written to node ND1, and the potential "Vref" of wiring 127 is written to node ND2.

[0097] At this time, if the potential difference across both ends of capacitor element 111 is V1, the potential difference V1 can be expressed by Equation (1).

[0098] V1 = Vdata - Vref (1)

[0099] Similarly, if the potential difference across both ends of capacitor element 112 is V2, the potential difference V2 can be expressed by Equation (2).

[0100] V2 = Vano - Vref (2)

[0101] At time T2, when the potential of wiring 121 is "Low" and the potential of wiring 122 is "Low", transistors 102 and 104 become non - conductive.

[0102] At this time, the potential V of node ND1 ND1 can be expressed by Equation (3). The potential V of node ND2 ND2 can be expressed by Equation (4).

[0103] V ND1 = Vdata - a (3)

[0104] V ND2 = Vref - b (4)

[0105] At this time, the potential difference V1 across both ends of the capacitive element 111 can be expressed by Equation (5). The potential difference V2 across both ends of the capacitive element 112 can be expressed by Equation (6).

[0106] V1 = (Vdata - a) - (Vref - b) (5)

[0107] V2 = Vano - (Vref - b) (6)

[0108] Here, a is a constant, indicating the amount of potential fluctuation due to effects such as feed - through and charge injection when the transistor 102 is in the non - conducting state. b is a constant, indicating the amount of potential fluctuation due to effects such as feed - through and charge injection when the transistor 104 is in the non - conducting state.

[0109] Next, the operation of writing the image data “Vdata” as the second data to the node ND2 and boosting the potential of the node ND1 will be described.

[0110] At time T3, when the potential of the wiring 121 is set to “Low” and the potential of the wiring 122 is set to “High”, the transistor 103 becomes conductive, and the potential “Vdata” of the wiring 131 is written to the node ND2.

[0111] At this time, since the potential difference V1 across both ends of the capacitive element 111 retains the potential difference V1 shown in Equation (5), the potential V of the node ND1 ND1 can be expressed by Equation (7). The potential V of the node ND2 ND2 can be expressed by Equation (8).

[0112] V ND1 = 2Vdata - Vref - a + b (7)

[0113] V ND2 = Vdata (8)

[0114] At time T4, when the potential of wiring 121 is set to "Low" and the potential of wiring 122 is set to "Low", transistor 103 becomes non-conductive, and the gate-source voltage Vgs of transistor 101 becomes the sum of the voltages held in capacitor elements 111 and 112 respectively, and a current corresponding to Vgs flows through light-emitting device 114.

[0115] At this time, the potential V of node ND1 ND1 can be expressed by Equation (9). The potential V of node ND2 ND2 can be expressed by Equation (10).

[0116] V ND1 = 2Vdata - Vref - a + b - c (9)

[0117] V ND2 = Vdata - c (10)

[0118] Here, c is a constant, indicating the amount of potential fluctuation due to feed-through, charge injection, etc. when transistor 103 becomes non-conductive.

[0119] Here, in Equation (9), when Vref is set to "0V" and constants a, b, and c are set to zero, V ND1 can be expressed as "2Vdata", which is obtained as a value higher than the potential "Vdata" supplied to pixel 10. That is, it boosts the voltage to a value higher than the voltage (Vdata) corresponding to the image data supplied to pixel 10 and supplies this voltage to transistor 101 that functions as a driving transistor. Therefore, the current flowing through light-emitting device 114 can be increased, and a display device with high brightness can be achieved.

[0120] The operation of FIG. 2 can be continuously performed within one horizontal period.

[0121] A display device according to one aspect of the present invention can generate a high voltage even when using a general-purpose driver IC. For example, since the voltage supplied from the driver IC for driving a light-emitting device or the like can be set to about 1 / 2, the display device can be made to consume less power. Further, for example, by writing the same image data twice, the current flowing through the light-emitting device can be increased, and the luminance of the display can be enhanced.

[0122] By combining such first data and second data, up-conversion, HDR display, correction of display unevenness specific to the display device, correction of the threshold voltage of the transistor included in the pixel, and the like can be performed. Or, these can be performed in combination.

[0123] In the up-conversion operation, for example, different correction data is supplied to each of four adjacent pixels (for two rows and two columns), and the same image data is supplied to these pixels. The supplied image data is corrected (converted) into different image data at each pixel, and display at each pixel can be performed. For example, by inputting data applied to a specific one pixel of 4K2K data to specific four pixels of a display device having a pixel count of 8K4K and inputting different correction data to each of the four pixels, a display with improved resolution can be performed.

[0124] A display device according to one aspect of the present invention is, in a broad sense, correction of image data, but different images can be superimposed and displayed. For example, a composite image in which a first image composed of image data “Vdata” and a second image composed of correction data “Vw” are superimposed can be displayed. In such a combination of image data and correction data, in addition to the composite display of different images, the luminance of the entire display image can be improved. For example, it can be applied to character insertion, AR display, and the like.

[0125] <Example configuration of pixel 2> Configurations different from the pixel 10 shown in FIG. 1 are shown in FIGS. 3A, 3B, and 4.

[0126] As shown in FIG. 3A, the transistor 101, the transistor 102, the transistor 103, and the transistor 104 may each have a configuration with a back gate. In particular, the transistor 101 that functions as a driving transistor preferably has a back gate. FIG. 3A shows a configuration in which the back gate of the transistor 101 is electrically connected to one of the source or the drain, and has an effect of enhancing the saturation of transistor characteristics. Also, FIG. 3A shows a configuration in which the back gates of the transistor 102, the transistor 103, and the transistor 104 are each electrically connected to the gate (which may be referred to as the front gate), and has an effect of increasing the on-current.

[0127] As shown in FIG. 3B, the back gate of the transistor 101 may be electrically connected to the front gate. By adopting such a configuration, it has an effect of increasing the on-current of the transistor 101.

[0128] As shown in FIG. 4, it is also possible to adopt a configuration in which the back gate is electrically connected to a wiring capable of supplying a fixed potential to control the threshold voltage of the transistor. In FIGS. 3A, 3B, and 4, although a configuration in which all transistors are provided with back gates is illustrated, it may also have transistors without back gates.

[0129] <Example configuration 3 of pixel> A configuration different from the pixel 10 shown in FIG. 3A is shown in FIG. 5.

[0130] The pixel 10 shown in FIG. 5 is different from the pixel 10 shown in FIG. 3A in that it has a transistor 105. One of the source or the drain of the transistor 105 is electrically connected to one electrode of the light-emitting device 114. The other of the source or the drain of the transistor 105 is electrically connected to the wiring 143. The gate of the transistor 105 is electrically connected to the wiring 141. The wiring 141 functions as a scanning line for controlling the operation of the transistor 105.

[0131] The transistor 105 can have a function of resetting the potential of one electrode of the light-emitting device 114 to the potential of the wiring 143. By resetting the potential of one electrode of the light-emitting device 114, it has a function of suppressing problems such as an unintended current flowing through the light-emitting device 114.

[0132] The transistor 105 can be configured to be electrically connected to a circuit (not shown) that has a function of monitoring current via the wiring 141. Thus, when a predetermined potential is applied to the gate of the transistor 101, the current flowing at that time can be made to flow through the transistor 105 and the wiring 141 into the circuit, making it possible to monitor the electrical characteristics of the transistor 101. By calculating variations in the threshold voltage and mobility of the transistor 101 from the current flowing through the circuit and applying data for correcting the threshold voltage to the transistor 101, a display device with less display unevenness can be obtained.

[0133] The transistor 105 may have a configuration with a back gate. FIG. 5 shows a configuration in which the back gate of the transistor 105 is electrically connected to the gate (front gate). Note that the back gate of the transistor 105 may be configured to be electrically connected to one of the source or drain. Also, the transistor 105 may have a configuration without a back gate.

[0134] <Configuration example 4 of pixel> A configuration different from the pixel 10 shown in FIG. 1 is shown in FIG. 6.

[0135] In the pixel 10A shown in FIG. 6, p-channel type transistors are applied to the transistors 101, 102, 103, and 104. Since the connection relationships of the light-emitting device 114, each transistor, each capacitive element, and each wiring can be referred to the description of the pixel 10 shown in FIG. 1, detailed description is omitted.

[0136] <Operation example 2 of pixel> Using the timing chart shown in FIG. 7, an example of the boosting operation of the pixel 10A shown in FIG. 6 will be described. "Vref" can be set to a high potential. As "Vref", for example, the same potential as the potential "Vano" of the wiring 128 can be used.

[0137] First, the operation of writing the image data "Vdata" as the first data to the node ND1 will be described. Here, in terms of potential distribution, coupling, or loss, detailed changes due to circuit configuration, operation timing, etc. are not considered.

[0138] At time T11, when the potential of the wiring 121 is "Low", the potential of the wiring 122 is "High", the potential of the wiring 131 is "Vdata", and the potential of the wiring 127 is "Vref", the transistors 102 and 104 become conductive, and the potential "Vdata" of the wiring 131 is written to the node ND1, and the potential "Vref" of the wiring 127 is written to the node ND2.

[0139] At this time, the potential difference V1 across both ends of the capacitor element 111 can be expressed by Equation (11). The potential difference V2 across both ends of the capacitor element 112 can be expressed by Equation (12).

[0140] V1 = Vref - Vdata (11)

[0141] V2 = Vref - Vano (12)

[0142] At time T12, when the potential of the wiring 121 is "High" and the potential of the wiring 122 is "High", the transistors 102 and 104 become non-conductive.

[0143] At this time, the potential V of the node ND1 ND1 can be expressed by Equation (13). The potential V of the node ND2 ND2 can be expressed by Equation (14).

[0144] V ND1 = Vdata + a (13)

[0145] V ND2 = Vref + b (14)

[0146] At this time, the potential difference V1 across both ends of the capacitor element 111 can be expressed by Equation (15). The potential difference V2 across both ends of the capacitor element 112 can be expressed by Equation (16).

[0147] V1 = (Vref + b) - (Vdata + a) (15)

[0148] V2 = (Vref + b) - Vano (16)

[0149] Next, the operation of writing the image data “Vdata” as the second data to the node ND2 and boosting the potential of the node ND1 will be described.

[0150] At time T13, when the potential of the wiring 121 is set to “High” and the potential of the wiring 122 is set to “Low”, the transistor 103 becomes conductive, and the potential “Vdata” of the wiring 131 is written to the node ND2.

[0151] At this time, since the potential difference across both ends of the capacitor element 111 is the potential difference V1 shown in Equation (15), the potential V ND1 of the node ND1 can be expressed by Equation (17). The potential V ND2 of the node ND2 can be expressed by Equation (18).

[0152] V ND1 = 2Vdata - Vref + a - b (17)

[0153] V ND2 = Vdata (18)

[0154] At time T14, when the potential of the wiring 121 is set to “High” and the potential of the wiring 122 is set to “High”, the transistor 103 becomes non - conductive, and the gate - source voltage Vgs of the transistor 101 becomes the sum of the voltages held in the capacitor element 111 and the capacitor element 112 respectively, and a current corresponding to Vgs flows through the light - emitting device 114.

[0155] At this time, the potential V of the node ND1 ND1 can be expressed by Equation (19). The potential V of the node ND2 ND2 can be expressed by Equation (20).

[0156] V ND1 = 2Vdata - Vref + a - b + c (19)

[0157] V ND2 = Vdata + c (20)

[0158] As described above, the pixel 10A can boost the voltage to a voltage higher than the voltage (Vdata) corresponding to the supplied image data and supply the voltage to the transistor 101 that functions as a driving transistor. Therefore, the current flowing through the light-emitting device 114 can be increased, and a display device with high luminance can be obtained.

[0159] <Pixel layout example> Hereinafter, a layout example of the pixel 10 will be described.

[0160] An example of the layout of the pixel 10 shown in FIG. 3A is shown in FIG. 8A.

[0161] FIG. 8A shows the transistor 101, the transistor 102, the transistor 103, the transistor 104, the capacitor element 111, the capacitor element 112, the wiring 121, the wiring 122, the wiring 131, the wiring 127, and the wiring 128. FIG. 8B shows a circuit diagram corresponding to the layout shown in FIG. 8A. In FIGS. 8A and 8B, the light-emitting device 114 and the wiring 129 are omitted for clarity of the drawing.

[0162] FIG. 9 shows a configuration in the case where a pixel electrode 53 is provided in addition to the configuration of FIG. 8A. The pixel electrode 53 is electrically connected to the light-emitting device 114. Further, the light-emitting device 114 can be provided on the pixel electrode 53.

[0163] In FIG. 9, the pixel electrode 53 is provided so as to overlap with elements such as the transistor 101 and the capacitor element 111 that constitute the pixel 10, and wirings and the like. Such a configuration is effective particularly when using a top-emission type light-emitting device. By arranging the transistor 101 and the like below the pixel electrode 53 in this way, even if the occupied area of the pixel 10 is reduced, a large aperture ratio can be realized.

[0164] As shown in FIG. 9, it is preferable that the pixel electrode 53 does not overlap with the wiring 131 that functions as a signal line. By preventing the pixel electrode 53 from overlapping with the wiring 131, it is possible to suppress the change in the potential of the wiring 131 from affecting the potential of the pixel electrode 53. When it is necessary to arrange the pixel electrode 53 so as to overlap with the wiring 131, the ratio of the overlapping area to the area of the pixel electrode 53 may be 10% or less, preferably 5% or less.

[0165] <Configuration example of sub-pixel> Configuration examples of sub-pixels applicable to the display device according to one aspect of the present invention are shown in FIGS. 10, 11A, and 11B.

[0166] The pixel 10 shown in FIG. 10 has a sub-pixel 10R that exhibits red light, a sub-pixel 10G that exhibits green light, and a sub-pixel 10B that exhibits blue light, and shows an example in which these three sub-pixels constitute one pixel 10. In FIG. 10, together with the sub-pixels (two pixels 10) arranged in a 2-row and 3-column matrix, the wirings 121, 122, and 131 are also shown. The wirings 121 and 122 may each have an area that overlaps with the pixel electrode 53.

[0167] The sub-pixel 10R has a pixel electrode 53a, and the display area 51a of the sub-pixel 10R is located inside the pixel electrode 53a. The sub-pixel 10G has a pixel electrode 53b, and the display area 51b of the sub-pixel 10G is located inside the pixel electrode 53b. The sub-pixel 10B has a pixel electrode 53c, and the display area 51c of the sub-pixel 10B is located inside the pixel electrode 53c. In FIG. 10, an example is shown where the pixel electrodes 53a, 53b, and 53c have the same area, but they may have different areas. Also, the display areas 51a, 51b, and 51c may have different areas respectively.

[0168] The pixel 10 shown in FIG. 10 shows an example where the positions of sub-pixels of the same color are shifted in the extending directions of the wirings 121 and 122. In other words, in the pixel 10, sub-pixels of the same color are arranged in a zigzag pattern in the extending directions of the wirings 121 and 122.

[0169] In FIG. 10, an example is shown where the combination of colors of light emitted by the sub-pixels is three colors: red (R), green (G), and blue (B), but the combination of colors and the number of colors are not limited to this. The combination of colors of light emitted by the sub-pixels may be four colors: red (R), green (G), blue (B), and white (W), or four colors: red (R), green (G), blue (B), and yellow (Y). The color elements applied to the sub-pixels are not limited to the above, and cyan (C) and magenta (M) etc. may be combined.

[0170] The pixel 10 shown in FIG. 11A has a strip-like shape with a long length of the sub-pixel in the extending direction of the wiring 131, and is arranged in a stripe pattern in the extending directions of the wirings 121 and 122. Also, an example is shown where the sub-pixels 10R, 10G, and 10B are aligned in the extending directions of the wirings 121 and 122.

[0171] The pixel 10 shown in FIG. 11B shows an example where the sub-pixels are arranged in a stripe pattern and the positions of sub-pixels of the same color are shifted in the extending directions of the wirings 121 and 122. In other words, in the pixel 10, sub-pixels of the same color are arranged in a zigzag pattern in the extending directions of the wirings 121 and 122.

[0172] In the present specification and the like, the blue wavelength region is 400 nm or more and less than 490 nm, and blue light emission has at least one emission spectrum peak in the wavelength region. Further, the green wavelength region is 490 nm or more and less than 580 nm, and green light emission has at least one emission spectrum peak in the wavelength region. Further, the red wavelength region is 580 nm or more and 680 nm or less, and red light emission has at least one emission spectrum peak in the wavelength region.

[0173] <Configuration Example 1 of Display Device> Hereinafter, a display device according to one aspect of the present invention will be described in detail.

[0174] A block diagram showing a configuration example of the display device 100 is shown in FIG. 12. The display device 100 includes a pixel portion 150 having a plurality of pixels 10, a drive circuit portion 130, a drive circuit portion 140a, a drive circuit portion 140b, a wiring 121, a wiring 122, and a wiring 131.

[0175] The pixel section 150 has a plurality of pixels 10, and each pixel 10 can be arranged in a matrix. The drive circuit section 130 is electrically connected to the pixel 10 via the wiring 121. Also, the drive circuit section 130 is electrically connected to the pixel 10 via the wiring 122. The drive circuit section 130 functions as a gate line drive circuit (also referred to as a gate driver). Each of the plurality of pixels 10 is supplied with a signal from the drive circuit section 130 via the wiring 121 and the wiring 122, and its driving is controlled. The drive circuit section 140a is electrically connected to the pixel 10 via the wiring 131. The drive circuit section 140b is electrically connected to a pixel 10 different from the pixel 10 that is electrically connected to the drive circuit section 140a via the wiring 131. Each of the drive circuit section 140a and the drive circuit section 140b functions as a source line drive circuit (also referred to as a source driver). Each of the plurality of pixels 10 is supplied with a signal from the drive circuit section 140a or the drive circuit section 140b via the wiring 131, and its driving is controlled. FIG. 12 shows an example in which the pixels 10 in odd-numbered columns are electrically connected to the drive circuit section 140a and the pixels 10 in even-numbered columns are electrically connected to the drive circuit section 140b.

[0176] A display device according to one aspect of the present invention can operate at high speed even in a display device with a large number of pixels by having a plurality of drive circuit sections that function as source drivers. A display device according to one aspect of the present invention can be suitably used, for example, in a high-definition display device with 1000 ppi or more, 2000 ppi or more, or 5000 ppi or more.

[0177] Note that in FIG. 12, an example in which two drive circuit sections 140a and 140b are provided as drive circuit sections that function as source drivers is shown, but one aspect of the present invention is not limited to this. Three or more drive circuit sections that function as source drivers may be provided. Also, one drive circuit section that functions as a source driver may be provided.

[0178] A schematic diagram showing a configuration example of the display device 100 is shown in FIG. 13A. The display device 100 has a stacked structure including a first layer 20 and a second layer 30 on the first layer 20. In FIG. 13A, a configuration in which the second layer 30 is provided on the first layer 20 is shown, but one aspect of the present invention is not limited to this. The first layer 20 may be provided on the second layer 30. One or more of an interlayer insulating layer and a wiring layer may be provided between the first layer 20 and the second layer 30. Also, the interlayer insulating layer and the wiring layer provided between the first layer 20 and the second layer 30 may each be plural.

[0179] The first layer 20 has a drive circuit section 140a and a drive circuit section 140b. The second layer 30 has a drive circuit section 130 and a pixel section 150.

[0180] Configuration examples of the first layer 20 and the second layer 30 shown in FIG. 13A are shown in FIG. 13B. In FIG. 13B, the positional relationship between the first layer 20 and the second layer 30 is indicated by white circles and a one-dot chain line. In a plan view, the white circles of the first layer 20 and the white circles of the second layer 30 connected by the one-dot chain line overlap. Note that the same notation is used in other figures. Note that, for clarity of the figure, FIG. 13B omits wirings other than the wiring 121, the wiring 122, and the wiring 131.

[0181] It is preferable that each of the drive circuit section 140a and the drive circuit section 140b provided in the first layer 20 of the display device 100 has a region overlapping with the pixel section 150. By laminating and providing the pixel section 150 and the regions where the drive circuit section 140a and the drive circuit section 140b overlap, the area of the frame, which is the region where the pixel section 150 is not provided, can be reduced. Therefore, the frame of the display device 100 can be made narrower. Also, by making the frame of the display device 100 narrower, the display device 100 can be made smaller.

[0182] In FIG. 13B, an example is shown in which the sizes of the first layer 20 and the second layer 30 are substantially the same. However, the gist of the present invention is not limited to this. The sizes of the first layer 20 and the second layer 30 may be different. For example, the first layer 20 may be larger than the second layer 30. Also, the first layer 20 may be smaller than the second layer 30.

[0183] After forming the first layer 20, the second layer 30 can be formed on the first layer 20 to fabricate the display device 100. By forming the second layer 30 on the first layer 20, the alignment accuracy between the first layer 20 and the second layer 30 can be improved. Therefore, the productivity of the display device 100 can be enhanced.

[0184] After forming the first layer 20 and the second layer 30 respectively, the first layer 20 and the second layer 30 may be bonded together to fabricate the display device 100. When fabricating the display device 100 by bonding the first layer 20 and the second layer 30 together, the sizes of the first layer 20 and the second layer 30 may be different. Therefore, the first layer 20 and the second layer 30 can be formed without being affected by each other's sizes. For example, a plurality of first layers 20 can be formed on the substrate to be formed with the first layer 20, and after dividing each of the first layers 20, the display device 100 can be fabricated by bonding it to the second layer 30. Similarly, for the second layer 30, a plurality of second layers 30 can be formed on the substrate to be formed with the second layer 30, and after dividing each of the second layers 30, the display device 100 can be fabricated by bonding it to the first layer 20. That is, the productivity of the first layer 20 and the second layer 30 can be enhanced, and at the same time, the productivity of the display device 100 can be enhanced.

[0185] <Configuration Example 2 of Display Device> A configuration example different from the display device 100 shown in FIGS. 13A and 13B is shown in FIGS. 14A and 14B. The display device 100 shown in FIGS. 14A and 14B is mainly different from the display device 100 shown in FIGS. 13A and 13B in that the first layer 20 has a drive circuit portion 130. By providing the drive circuit portion 130 in the same first layer 20 as the drive circuit portions 140a and 140b, the manufacturing processes of the drive circuit portion 130 and the drive circuit portions 140a and 140b can be made common, and productivity can be improved.

[0186] In FIG. 14B, an example in which the pixel portion 150 does not have an area overlapping with the drive circuit portion 130 is shown, but one aspect of the present invention is not limited to this. The pixel portion 150 may have an area overlapping with the drive circuit portion 130. Further, the pixel portion 150 may have an area overlapping with any of the drive circuit portion 130, the drive circuit portion 140a, and the drive circuit portion 140b. With such a configuration, the frame of the display device 100 can be narrowed. Further, by narrowing the frame of the display device 100, the display device 100 can be made smaller.

[0187] <Cross-sectional configuration example 1 of display device> A cross-sectional view showing a configuration example of the display device 100 is shown in FIG. 15. The display device 100 has a substrate 701 and a substrate 705, and the substrate 701 and the substrate 705 are bonded together by a sealing material 712.

[0188] As the substrate 701, a single crystal semiconductor substrate such as a single crystal silicon substrate can be used. Note that a semiconductor substrate other than the single crystal semiconductor substrate may be used as the substrate 701.

[0189] Transistors 441 and 601 are provided on a substrate 701. Transistors 441 and 601 can be transistors provided in a first layer 20. For example, in the display device 100 shown in FIGS. 13A and 13B, transistors 441 and 601 can be transistors provided in a driving circuit section 140a or a driving circuit section 140b. For example, in the display device 100 shown in FIGS. 14A and 14B, transistors 441 and 601 can be transistors provided in a driving circuit section 130, a driving circuit section 140a, or a driving circuit section 140b.

[0190] Transistor 441 includes a conductor 443 having a function as a gate electrode, an insulator 445 having a function as a gate insulator, and a part of the substrate 701, and has a semiconductor region 447 including a channel formation region, a low resistance region 449a having a function as one of a source region or a drain region, and a low resistance region 449b having a function as the other of the source region or the drain region. Transistor 441 can be either a p-channel type or an n-channel type.

[0191] Transistor 441 is electrically separated from other transistors by an element isolation layer 403. FIG. 15 shows a case where transistor 441 and transistor 601 are electrically separated by element isolation layer 403. Element isolation layer 403 can be formed using a method such as LOCOS (LOCal Oxidation of Silicon) method or STI (Shallow Trench Isolation) method.

[0192] Here, in the transistor 441 shown in FIG. 15, the semiconductor region 447 has a convex shape. Also, the side surface and the upper surface of the semiconductor region 447 are provided so as to be covered by the conductor 443 via the insulator 445. Note that in FIG. 15, the state where the conductor 443 covers the side surface of the semiconductor region 447 is not illustrated. Also, a material for adjusting the work function can be used for the conductor 443.

[0193] A transistor in which a semiconductor region such as transistor 441 has a convex shape can be called a fin-type transistor because it utilizes the convex portion of the semiconductor substrate. Note that an insulator having a function as a mask for forming the convex portion may be provided in contact with the upper portion of the convex portion. Also, although FIG. 15 shows a configuration in which a part of the substrate 701 is processed to form a convex portion, an SOI substrate may be processed to form a semiconductor having a convex shape.

[0194] Note that the configuration of the transistor 441 shown in FIG. 15 is an example and is not limited to that configuration, and an appropriate configuration may be adopted according to the circuit configuration or the operation method of the circuit. For example, the transistor 441 may be a planar-type transistor.

[0195] The transistor 601 can have the same configuration as the transistor 441.

[0196] On the substrate 701, an element isolation layer 403, and in addition to the transistors 441 and 601, insulators 405, 407, 409, and 411 are provided. Conductors 451 are embedded in the insulator 405, the insulator 407, the insulator 409, and the insulator 411. Here, the height of the upper surface of the conductor 451 and the height of the upper surface of the insulator 411 can be made approximately the same.

[0197] Insulators 413 and 415 are provided on the conductor 451 and on the insulator 411. Also, conductors 457 are embedded in the insulator 413 and in the insulator 415. Here, the height of the upper surface of the conductor 457 and the height of the upper surface of the insulator 415 can be made approximately the same.

[0198] Insulators 417 and 419 are provided on the conductor 457 and on the insulator 415. Also, conductors 459 are embedded in the insulator 417 and in the insulator 419. Here, the height of the upper surface of the conductor 459 and the height of the upper surface of the insulator 419 can be made approximately the same.

[0199] An insulator 421 and an insulator 214 are provided on a conductor 459 and on an insulator 419. A conductor 453 is embedded in the insulator 421 and in the insulator 214. Here, the height of the upper surface of the conductor 453 and the height of the upper surface of the insulator 214 can be made approximately the same.

[0200] An insulator 216 is provided on a conductor 453 and on an insulator 214. A conductor 455 is embedded in the insulator 216. Here, the height of the upper surface of the conductor 455 and the height of the upper surface of the insulator 216 can be made approximately the same.

[0201] An insulator 222, an insulator 224, an insulator 254, an insulator 244, an insulator 280, an insulator 274, and an insulator 281 are provided on a conductor 455 and on an insulator 216. A conductor 305 is embedded in the insulator 222, in the insulator 224, in the insulator 254, in the insulator 244, in the insulator 280, in the insulator 274, and in the insulator 281. Here, the height of the upper surface of the conductor 305 and the height of the upper surface of the insulator 281 can be made approximately the same.

[0202] An insulator 361 is provided on a conductor 305 and on an insulator 281. A conductor 317 and a conductor 337 are embedded in the insulator 361. Here, the height of the upper surface of the conductor 337 and the height of the upper surface of the insulator 361 can be made approximately the same.

[0203] An insulator 363 is provided on a conductor 337 and on an insulator 361. A conductor 347, a conductor 353, a conductor 355, and a conductor 357 are embedded in the insulator 363. Here, the height of the upper surface of the conductor 353, the height of the upper surface of the conductor 355, and the height of the upper surface of the conductor 357 and the height of the upper surface of the insulator 363 can be made approximately the same.

[0204] A connection electrode 760 is provided on the conductor 353, on the conductor 355, on the conductor 357, and on the insulator 363. An anisotropic conductor 780 is provided so as to be electrically connected to the connection electrode 760, and an FPC (Flexible Printed Circuit) 716 is provided so as to be electrically connected to the anisotropic conductor 780. Various signals and the like are supplied to the display device 100 from the outside of the display device 100 by the FPC 716.

[0205] As shown in FIG. 15, the low-resistance region 449b having a function as the other of the source region or the drain region of the transistor 441 is electrically connected to the FPC 716 via the conductors 451, 457, 459, 453, 455, 305, 317, 337, 347, 353, 355, 357, the connection electrode 760, and the anisotropic conductor 780. Here, in FIG. 15, three conductors 353, 355, and 357 are shown as the conductors having a function of electrically connecting the connection electrode 760 and the conductor 347, but one aspect of the present invention is not limited to this. The number of conductors having a function of electrically connecting the connection electrode 760 and the conductor 347 may be one, two, or four or more. By providing a plurality of conductors having a function of electrically connecting the connection electrode 760 and the conductor 347, the contact resistance can be reduced.

[0206] A transistor 750 is provided on the insulator 214. The transistor 750 can be a transistor provided in the second layer 30. For example, in the display device 100 shown in FIGS. 13A, 13B, 14A, and 14B, the transistor 750 can be a transistor provided in the pixel portion 150. As the transistor 750, an OS transistor can be preferably used. The OS transistor has a feature that the off-current is extremely small. Therefore, since the holding time of an image signal or the like can be lengthened, the frequency of the refresh operation can be reduced. Therefore, the power consumption of the display device 100 can be reduced.

[0207] In insulator 254, in insulator 244, in insulator 280, in insulator 274, and in insulator 281, conductor 301a and conductor 301b are embedded. Conductor 301a is electrically connected to one of the source or drain of transistor 750, and conductor 301b is electrically connected to the other of the source or drain of transistor 750. Here, the height of the upper surfaces of conductor 301a and conductor 301b can be made approximately the same as the height of the upper surface of insulator 281.

[0208] In insulator 361, conductor 311, conductor 313, conductor 331, capacitor element 790, conductor 333, and conductor 335 are embedded. Conductor 311 and conductor 313 are electrically connected to transistor 750 and have the function of wiring. Conductor 333 and conductor 335 are electrically connected to capacitor element 790. Here, the height of the upper surfaces of conductor 331, conductor 333, and conductor 335 can be made approximately the same as the height of the upper surface of insulator 361.

[0209] In insulator 363, conductor 341, conductor 343, and conductor 351 are embedded. Here, the height of the upper surface of conductor 351 can be made approximately the same as the height of the upper surface of insulator 363.

[0210] Insulators 405, 407, 409, 411, 413, 415, 417, 419, 421, 214, 280, 274, 281, 361, and 363 have the function of an interlayer film and may also have the function of a planarization film that covers the uneven shape below each of them. For example, the upper surface of insulator 363 may be planarized by a planarization process using a chemical mechanical polishing (CMP) method or the like to enhance flatness.

[0211] For example, in the display device 100 shown in FIGS. 13 and 14, capacitor element 790 can be capacitor element 111 or capacitor element 112 provided in pixel portion 150.

[0212] As shown in FIG. 15, the capacitive element 790 has a lower electrode 321 and an upper electrode 325. An insulator 323 is provided between the lower electrode 321 and the upper electrode 325. That is, the capacitive element 790 has a stacked structure in which an insulator 323 that functions as a dielectric is sandwiched between a pair of electrodes. Note that FIG. 15 shows an example in which the capacitive element 790 is provided on the insulator 281, but the capacitive element 790 may be provided on an insulator different from the insulator 281.

[0213] In FIG. 15, an example in which the conductors 301a, 301b, and 305 are formed in the same layer is shown. An example in which the conductors 311, 313, 317, and the lower electrode 321 are formed in the same layer is shown. An example in which the conductors 331, 333, 335, and 337 are formed in the same layer is shown. An example in which the conductors 341, 343, and 347 are formed in the same layer is shown. Further, an example in which the conductors 351, 353, 355, and 357 are formed in the same layer is shown. By forming a plurality of conductors in the same layer, the manufacturing process of the display device 100 can be simplified, so that the manufacturing cost of the display device 100 can be reduced. Note that these may be formed in different layers and may have different types of materials.

[0214] The display device 100 shown in FIG. 15 includes a light-emitting device 782. The light-emitting device 782 includes a conductor 772, an EL layer 786, and a conductor 788. The EL layer 786 includes an organic compound or an inorganic compound such as quantum dots.

[0215] Examples of materials that can be used for the organic compound include a fluorescent material and a phosphorescent material. Examples of materials that can be used for the quantum dots include a colloidal quantum dot material, an alloy-type quantum dot material, a core-shell-type quantum dot material, and a core-type quantum dot material.

[0216] The conductor 772 is electrically connected to the other of the source or drain of the transistor 750 via the conductors 351, 341, 331, 313, and 301b. The conductor 772 is formed on the insulator 363 and has the function of a pixel electrode.

[0217] For the conductor 772, a material that is transparent to visible light or a reflective material can be used. As the transparent material, for example, an oxide material containing indium, zinc, tin, etc. may be used. As the reflective material, for example, a material containing aluminum, silver, etc. may be used.

[0218] Although not shown in FIG. 15, the display device 100 can be provided with optical members (optical substrates) such as a polarizing member, a retardation member, and an antireflection member.

[0219] On the substrate 705 side, a light-shielding layer 738 and an insulator 734 in contact therewith are provided. The light-shielding layer 738 has a function of blocking light emitted from adjacent regions. Or, the light-shielding layer 738 has a function of blocking external light from reaching the transistor 750 or the like.

[0220] In the display device 100 shown in FIG. 15, an insulator 730 is provided on the insulator 363. Here, the insulator 730 can be configured to cover a part of the conductor 772. Also, the light-emitting device 782 has a transparent conductor 788 and can be a top-emission type light-emitting device. Note that the light-emitting device 782 may have a bottom-emission structure that emits light toward the conductor 772 side, or a dual-emission structure that emits light toward both the conductor 772 and the conductor 788.

[0221] Note that the light-shielding layer 738 is provided so as to have a region overlapping with the insulator 730. Also, the light-shielding layer 738 is covered with the insulator 734. Also, the space between the light-emitting device 782 and the insulator 734 is filled with a sealing layer 732.

[0222] Furthermore, the structure 778 is provided between the insulator 730 and the EL layer 786. Also, the structure 778 is provided between the insulator 730 and the insulator 734.

[0223] A modified example of the display device 100 shown in FIG. 15 is shown in FIG. 16. The display device 100 shown in FIG. 16 is different from the display device 100 shown in FIG. 15 in that it is provided with a coloring layer 736. Note that the coloring layer 736 is provided so as to have a region overlapping with the light-emitting device 782. By providing the coloring layer 736, the color purity of the light extracted from the light-emitting device 782 can be enhanced. Thereby, a high-quality image can be displayed on the display device 100. Also, since, for example, all the light-emitting devices 782 of the display device 100 can be light-emitting devices that emit white light, it is not necessary to form the EL layer 786 by painting, and the display device 100 can be made high-definition.

[0224] The light-emitting device 782 can have a microcavity structure. Thereby, light of a predetermined color (for example, RGB) can be extracted without providing a coloring layer, and the display device 100 can perform color display. By adopting a configuration without a coloring layer, absorption of light by the coloring layer can be suppressed. Thereby, the display device 100 can display a high-brightness image, and the power consumption of the display device 100 can be reduced. Note that even when the EL layer 786 is formed in an island shape for each pixel or in a stripe shape for each pixel column, that is, by painting, a configuration without a coloring layer can be adopted.

[0225] In FIGS. 15 and 16, the transistors 441 and 601 are provided such that a channel formation region is formed inside the substrate 701, and the OS transistors are provided by laminating them on the transistors 441 and 601. However, one aspect of the present invention is not limited to this. A modified example of FIG. 16 is shown in FIG. 17. The display device 100 shown in FIG. 17 mainly differs from the display device 100 shown in FIG. 16 in that it has transistors 602 and 603, which are OS transistors, instead of the transistors 441 and 601. Also, the transistor 750 can use an OS transistor. That is, in the display device 100 shown in FIG. 17, the OS transistors are laminated and provided.

[0226] An insulator 613 and an insulator 614 are provided on the substrate 701, and the transistors 602 and 603 are provided on the insulator 614. Note that transistors or the like may be provided between the substrate 701 and the insulator 613. For example, transistors having the same configuration as the transistors 441 and 601 shown in FIG. 16 may be provided between the substrate 701 and the insulator 613.

[0227] The transistors 602 and 603 can be transistors provided in the first layer 20. For example, in the display device 100 shown in FIGS. 13A and 13B, the transistors 602 and 603 can be transistors provided in the drive circuit section 140a or the drive circuit section 140b. For example, in the display device 100 shown in FIGS. 14A and 14B, the transistors 602 and 603 can be transistors provided in the drive circuit section 130, the drive circuit section 140a, or the drive circuit section 140b.

[0228] The transistors 602 and 603 can be transistors having the same configuration as the transistor 750. Note that the transistors 602 and 603 may be OS transistors having a configuration different from that of the transistor 750.

[0229] On the insulator 614, in addition to the transistors 602 and 603, insulators 616, 622, 624, 654, 644, 680, 674, and insulator 681 are provided. In the insulators 654, 644, 680, 674, and 681, the conductor 461 is embedded. Here, the height of the upper surface of the conductor 461 and the height of the upper surface of the insulator 681 can be made approximately the same.

[0230] An insulator 501 is provided on the conductor 461 and on the insulator 681. A conductor 463 is embedded in the insulator 501. Here, the height of the upper surface of the conductor 463 and the height of the upper surface of the insulator 501 can be made approximately the same.

[0231] An insulator 503 is provided on the conductor 463 and on the insulator 501. A conductor 465 is embedded in the insulator 503. Here, the height of the upper surface of the conductor 465 and the height of the upper surface of the insulator 503 can be made approximately the same.

[0232] An insulator 505 is provided on the conductor 465 and on the insulator 503. Also, a conductor 467 is embedded in the insulator 505. Here, the height of the upper surface of the conductor 467 and the height of the upper surface of the insulator 505 can be made approximately the same.

[0233] An insulator 507 is provided on the conductor 467 and on the insulator 505. A conductor 469 is embedded in the insulator 507. Here, the height of the upper surface of the conductor 469 and the height of the upper surface of the insulator 507 can be made approximately the same.

[0234] An insulator 509 is provided on the conductor 469 and on the insulator 507. Also, a conductor 471 is embedded in the insulator 509. Here, the height of the upper surface of the conductor 471 and the height of the upper surface of the insulator 509 can be made approximately the same.

[0235] An insulator 421 and an insulator 214 are provided on a conductor 471 and on an insulator 509. A conductor 453 is embedded in the insulator 421 and in the insulator 214. Here, the height of the upper surface of the conductor 453 and the height of the upper surface of the insulator 214 can be made approximately the same.

[0236] As shown in FIG. 17, one of the source or drain of the transistor 602 is electrically connected to the FPC 716 via a conductor 461, a conductor 463, a conductor 465, a conductor 467, a conductor 469, a conductor 471, a conductor 453, a conductor 455, a conductor 305, a conductor 317, a conductor 337, a conductor 347, a conductor 353, a conductor 355, a conductor 357, a connection electrode 760, and an anisotropic conductor 780.

[0237] The insulators 613, 614, 680, 674, 681, 501, 503, 505, 507, and 509 may have a function as an interlayer film and may also have a function as a planarization film that covers the uneven shapes below them.

[0238] By configuring the display device 100 as shown in FIG. 17, while making the display device 100 have a narrow bezel and be miniaturized, all the transistors included in the display device 100 can be made OS transistors. As a result, for example, the transistors provided in the first layer 20 and the transistors provided in the second layer 30 can be manufactured using the same device. Therefore, the manufacturing cost of the display device 100 can be reduced, and the display device 100 can be made inexpensive.

[0239] <Example of cross-sectional configuration of display device 2> FIG. 18 is a cross-sectional view showing a configuration example of the display device 100. It is mainly different from the display device 100 shown in FIG. 16 in that a layer having a transistor 800 is provided between the layer having the transistor 750 and the layer having the transistors 601 and 441.

[0240] The first layer 20 shown in FIG. 13A etc. can be formed into a stacked structure of a first circuit layer and a second circuit layer on the first circuit layer. For example, the transistor 601 and the transistor 441 can be transistors provided in the first circuit layer. The transistor 800 can be a transistor provided in the second circuit layer. The transistor 750 can be a transistor provided in the second layer 30.

[0241] An insulator 821 and an insulator 814 are provided on the conductor 459 and on the insulator 419. A conductor 853 is embedded in the insulator 821 and in the insulator 814. Here, the height of the upper surface of the conductor 853 and the height of the upper surface of the insulator 814 can be made about the same.

[0242] An insulator 816 is provided on the conductor 853 and on the insulator 814. A conductor 855 is embedded in the insulator 816. Here, the height of the upper surface of the conductor 855 and the height of the upper surface of the insulator 816 can be made about the same.

[0243] An insulator 822, an insulator 824, an insulator 854, an insulator 844, an insulator 880, an insulator 874, and an insulator 881 are provided on the conductor 855 and on the insulator 816. A conductor 805 is embedded in the insulator 822, in the insulator 824, in the insulator 854, in the insulator 844, in the insulator 880, in the insulator 874, and in the insulator 881. Here, the height of the upper surface of the conductor 805 and the height of the upper surface of the insulator 881 can be made about the same.

[0244] An insulator 421 and an insulator 214 are provided on the conductor 817 and on the insulator 881.

[0245] As shown in FIG. 18, a low-resistance region 449b having a function as the other of the source region or the drain region of the transistor 441 is electrically connected to the FPC 716 via a conductor 451, a conductor 457, a conductor 459, a conductor 853, a conductor 855, a conductor 805, a conductor 817, a conductor 453, a conductor 455, a conductor 305, a conductor 317, a conductor 337, a conductor 347, a conductor 353, a conductor 355, a conductor 357, a connection electrode 760, and an anisotropic conductor 780.

[0246] A transistor 800 is provided on the insulator 814. The transistor 800 can be a transistor provided in the second layer 30. For example, in the display device 100 shown in FIGS. 13A and 13B, the transistor 800 can be a transistor provided in the drive circuit unit 140a or the drive circuit unit 140b. For example, in the display device 100 shown in FIGS. 14A and 14B, the transistor 800 can be a transistor provided in the drive circuit unit 130, the drive circuit unit 140a, or the drive circuit unit 140b. The transistor 800 is preferably an OS transistor.

[0247] Conductors 801a and 801b are embedded in the insulator 854, the insulator 844, the insulator 880, the insulator 874, and the insulator 881. The conductor 801a is electrically connected to one of the source or the drain of the transistor 800, and the conductor 801b is electrically connected to the other of the source or the drain of the transistor 800. Here, the height of the upper surfaces of the conductor 801a and the conductor 801b can be made approximately the same as the height of the upper surface of the insulator 881.

[0248] The transistor 750 can be a transistor provided in the second layer 30. For example, in the display device 100 shown in FIGS. 13A, 13B, 14A, and 14B, the transistor 750 can be a transistor provided in the pixel portion 150. The transistor 750 is preferably an OS transistor.

[0249] Note that an OS transistor or the like may be provided between the layer in which the transistors 441 and 601 and the like are provided and the layer in which the transistor 800 and the like are provided. Further, an OS transistor or the like may be provided between the layer in which the transistor 800 and the like are provided and the layer in which the transistor 750 and the like are provided. Furthermore, an OS transistor or the like may be provided in a layer above the layer in which the transistor 750 and the like are provided.

[0250] The insulators 405, 407, 409, 411, 413, 415, 417, 419, 821, 814, 880, 874, 881, 421, 214, 280, 274, 281, 361, and 363 may have a function as an interlayer film and may also have a function as a planarization film that covers the uneven shape below each of them.

[0251] FIG. 18 shows an example in which the conductors 801a, 801b, and 805 are formed in the same layer. Further, an example in which the conductors 811, 813, and 817 are formed in the same layer is shown.

[0252] In FIG. 18, a configuration is shown in which the transistors 441 and 601 are provided such that a channel formation region is formed inside the substrate 701, and an OS transistor is provided by laminating on the transistors 441 and 601. However, one aspect of the present invention is not limited to this. A modified example of FIG. 18 is shown in FIG. 19. The display device 100 shown in FIG. 19 is different from the display device 100 shown in FIG. 18 in that it has transistors 602 and 603, which are OS transistors, instead of the transistors 441 and 601. That is, in the display device 100 shown in FIG. 19, the OS transistors are provided in three layers.

[0253] An OS transistor or the like may be provided between the layer in which transistors 602 and 603 are provided and the layer in which transistor 800 and the like are provided. Further, an OS transistor or the like may be provided between the layer in which transistor 800 and the like are provided and the layer in which transistor 750 or transistors 750 and the like are provided. Furthermore, an OS transistor or the like may be provided in a layer above the layer in which transistors 750 and the like are provided.

[0254] For example, transistors 602 and 603 can be transistors provided in the first circuit layer. Transistor 800 can be a transistor provided in the second circuit layer. Transistor 750 can be a transistor provided in the second layer 30.

[0255] Insulators 821 and 814 are provided on conductor 471 and on insulator 509. Conductor 853 is embedded in insulator 821 and in insulator 814. Here, the height of the upper surface of conductor 853 and the height of the upper surface of insulator 814 can be made about the same.

[0256] As shown in FIG. 19, one of the source or drain of transistor 602 is electrically connected to FPC 716 via conductors 461, 463, 465, 467, 469, 471, 853, 855, 805, 817, 453, 455, 305, 317, 337, 347, 353, 355, 357, connection electrode 760, and anisotropic conductor 780.

[0257] By configuring display device 100 as shown in FIG. 19, while making display device 100 have a narrow bezel and be miniaturized, all the transistors included in display device 100 can be OS transistors. As a result, it is not necessary to fabricate different types of transistors, so the manufacturing cost of display device 100 can be reduced, and display device 100 can be made inexpensive.

[0258] <Configuration Example of Light-Emitting Device> As the light-emitting device 572, for example, an EL element that utilizes electroluminescence can be applied. The EL element has a layer containing a light-emitting compound (hereinafter also referred to as the EL layer) between a pair of electrodes. When a potential difference larger than the threshold voltage of the EL element is generated between the pair of electrodes, holes are injected into the EL layer from the anode side, and electrons are injected from the cathode side. The injected electrons and holes recombine in the EL layer, and the light-emitting substance contained in the EL layer emits light.

[0259] EL elements are distinguished by whether the light-emitting material is an organic compound or an inorganic compound. Generally, the former is called an organic EL element, and the latter is called an inorganic EL element.

[0260] In an organic EL element, by applying a voltage, electrons are injected into the EL layer from one electrode, and holes are injected into the EL layer from the other electrode. Then, when these carriers (electrons and holes) recombine, a light-emitting organic compound forms an excited state and emits light when the excited state returns to the ground state. Due to such a mechanism, such a light-emitting device is called a current-excited type light-emitting device.

[0261] In this specification and the like, the voltage supplied to a display element such as a light-emitting device or a liquid crystal element indicates the difference between the potential applied to one electrode of the display element and the potential applied to the other electrode of the display element.

[0262] Note that, in addition to the light-emitting compound, the EL layer may have a substance with high hole injection property, a substance with high hole transport property, a hole blocking material, a substance with high electron transport property, a substance with high electron injection property, or a bipolar substance (a substance with high electron transport property and high hole transport property), etc.

[0263] The EL layer can be formed by methods such as a vapor deposition method (including a vacuum vapor deposition method), a transfer method, a printing method, an inkjet method, a coating method, etc.

[0264] Inorganic EL elements are classified into distributed inorganic EL elements and thin-film inorganic EL elements according to their device structures. A distributed inorganic EL element has a light-emitting layer in which particles of a light-emitting material are dispersed in a binder, and its light-emitting mechanism is donor-acceptor recombination light emission that utilizes a donor level and an acceptor level. A thin-film inorganic EL element has a structure in which a light-emitting layer is sandwiched between dielectric layers and further sandwiched between electrodes, and its light-emitting mechanism is localized light emission that utilizes inner-shell electron transitions of metal ions.

[0265] For a light-emitting device to extract light emission, at least one of a pair of electrodes may be transparent. Then, a transistor and a light-emitting device are formed on a substrate, and there are top emission structures that extract light emission from the surface opposite to the substrate, bottom emission structures that extract light emission from the surface on the substrate side, and dual emission structures that extract light emission from both surfaces. Any light-emitting device with any emission structure can be applied.

[0266] Figures 20A to 20E are diagrams showing a configuration example of a light-emitting device 572. Figure 20A shows a structure (single structure) in which an EL layer 786 is sandwiched between a conductor 772 and a conductor 788. As described above, the EL layer 786 contains a light-emitting material, for example, a light-emitting material that is an organic compound.

[0267] Figure 20B is a diagram showing a stacked structure of the EL layer 786. Here, in the light-emitting device 572 having the structure shown in Figure 20B, the conductor 772 functions as an anode, and the conductor 788 functions as a cathode.

[0268] The EL layer 786 has a structure in which a hole injection layer 721, a hole transport layer 722, a light-emitting layer 723, an electron transport layer 724, and an electron injection layer 725 are sequentially stacked on the conductor 772. When the conductor 772 functions as a cathode and the conductor 788 functions as an anode, the stacking order is reversed.

[0269] The light-emitting layer 723 has a combination of a light-emitting material and a plurality of materials as appropriate, and can be configured to obtain fluorescence or phosphorescence that exhibits a desired emission color. Further, the light-emitting layer 723 may have a laminated structure with different emission colors. In this case, different materials may be used for the light-emitting substances and other substances used in each of the laminated light-emitting layers.

[0270] In the light-emitting device 572, for example, by using the conductor 772 shown in FIG. 20B as a reflective electrode, the conductor 788 as a semi-transmissive / semi-reflective electrode, and forming a microcavity structure, the light emitted from the light-emitting layer 723 included in the EL layer 786 can be resonated between the two electrodes, and the light transmitted through the conductor 788 and emitted can be enhanced.

[0271] When the conductor 772 of the light-emitting device 572 is a reflective electrode having a laminated structure of a conductive material having reflectivity and a conductive material having translucency (transparent conductive film), optical adjustment can be performed by controlling the film thickness of the transparent conductive film. Specifically, it is preferable to adjust so that the electrode distance between the conductor 772 and the conductor 788 is in the vicinity of mλ / 2 (where m is a natural number) with respect to the wavelength λ of the light obtained from the light-emitting layer 723.

[0272] In order to amplify the desired light (wavelength: λ) obtained from the light-emitting layer 723, the optical distance from the conductor 772 to the region (light-emitting region) where the desired light of the light-emitting layer can be obtained, and the optical distance from the conductor 788 to the region (light-emitting region) where the desired light of the light-emitting layer 723 can be obtained are each preferably adjusted to be in the vicinity of (2m'+1)λ / 4 (where m' is a natural number). Here, the light-emitting region refers to the recombination region of holes and electrons in the light-emitting layer 723.

[0273] By performing such optical adjustment, the spectrum of a specific monochromatic light obtained from the light-emitting layer 723 can be narrowed, and light emission with good color purity can be obtained.

[0274] However, in the above case, the optical distance between the conductor 772 and the conductor 788 can strictly speaking be the total thickness from the reflection region in the conductor 772 to the reflection region in the conductor 788. However, since it is difficult to strictly determine the reflection regions in the conductor 772 and the conductor 788, it is assumed that the above effects can be sufficiently obtained by assuming arbitrary positions of the conductor 772 and the conductor 788 as the reflection regions. Also, the optical distance between the conductor 772 and the light-emitting layer from which desired light is obtained can strictly speaking be the optical distance between the reflection region in the conductor 772 and the light-emitting region in the light-emitting layer from which desired light is obtained. However, since it is difficult to strictly determine the reflection region in the conductor 772 and the light-emitting region in the light-emitting layer from which desired light is obtained, it is assumed that the above effects can be sufficiently obtained by assuming an arbitrary position of the conductor 772 as the reflection region and an arbitrary position of the light-emitting layer from which desired light is obtained as the light-emitting region.

[0275] Since the light-emitting device 572 shown in FIG. 20B has a microcavity structure, it is possible to extract light (monochromatic light) of different wavelengths even if it has the same EL layer. Therefore, painting (for example, RGB) for obtaining different emission colors becomes unnecessary. Therefore, it is easy to achieve high definition. Also, combination with a coloring layer is possible. Furthermore, since it is possible to enhance the emission intensity in the front direction of a specific wavelength, power consumption can be reduced.

[0276] Note that the light-emitting device 572 shown in FIG. 20B does not necessarily have a microcavity structure. In this case, the light-emitting layer 723 is structured to emit white light, and by providing a coloring layer, light of a predetermined color (for example, RGB) can be extracted. Also, when forming the EL layer 786, if painting for obtaining different emission colors is performed, light of a predetermined color can be extracted without providing a coloring layer.

[0277] At least one of the conductor 772 and the conductor 788 can be an electrode having translucency (such as a transparent electrode, a semi-transmissive / semi-reflective electrode, etc.). When the electrode having translucency is a transparent electrode, the transmittance of visible light of the transparent electrode shall be 40% or more. Also, in the case of a semi-transmissive / semi-reflective electrode, the reflectance of visible light of the semi-transmissive / semi-reflective electrode shall be 20% or more and 80% or less, preferably 40% or more and 70% or less. Also, the resistivity of these electrodes is preferably 1×10 -2 Ωcm or less.

[0278] When the conductor 772 or the conductor 788 is an electrode having reflectivity (reflective electrode), the reflectance of visible light of the electrode having reflectivity shall be 40% or more and 100% or less, preferably 70% or more and 100% or less. Also, the resistivity of this electrode is preferably 1×10 -2 Ωcm or less.

[0279] The configuration of the light-emitting device 572 may be the configuration shown in FIG. 20C. FIG. 20C shows a light-emitting device 572 having a laminated structure (tandem structure) in which two EL layers (EL layer 786a and EL layer 786b) are provided between the conductor 772 and the conductor 788, and a charge generation layer 792 is provided between the EL layer 786a and the EL layer 786b. By forming the light-emitting device 572 into a tandem structure, the current efficiency and external quantum efficiency of the light-emitting device 572 can be increased. Therefore, a high-brightness image can be displayed on the display device 100. Also, the power consumption of the display device 100 can be reduced. Here, the EL layer 786a and the EL layer 786b can have the same configuration as the EL layer 786 shown in FIG. 20B.

[0280] The charge generation layer 792 has a function of injecting electrons into one of the EL layer 786a and the EL layer 786b and injecting holes into the other when a voltage is supplied between the conductor 772 and the conductor 788. Therefore, when a voltage is supplied so that the potential of the conductor 772 becomes higher than the potential of the conductor 788, electrons are injected from the charge generation layer 792 into the EL layer 786a, and holes are injected from the charge generation layer 792 into the EL layer 786b.

[0281] Note that, from the viewpoint of light extraction efficiency, the charge generation layer 792 preferably transmits visible light (specifically, the transmittance of visible light of the charge generation layer 792 is 40% or more). Further, the conductivity of the charge generation layer 792 may be lower than the conductivity of the conductor 772 or the conductivity of the conductor 788.

[0282] The configuration of the light-emitting device 572 may be the configuration shown in FIG. 20D. In FIG. 20D, three EL layers (EL layer 786a, EL layer 786b, and EL layer 786c) are provided between the conductor 772 and the conductor 788, and a tandem-structured light-emitting device 572 having a charge generation layer 792 is shown between the EL layer 786a and the EL layer 786b and between the EL layer 786b and the EL layer 786c. Here, the EL layer 786a, the EL layer 786b, and the EL layer 786c can have the same configuration as the EL layer 786 shown in FIG. 20B. By configuring the light-emitting device 572 as shown in FIG. 20D, the current efficiency and the external quantum efficiency of the light-emitting device 572 can be further increased. Therefore, a higher-brightness image can be displayed on the display device 100. Further, the power consumption of the display device 100 can be further reduced.

[0283] The configuration of the light-emitting device 572 may be the configuration shown in FIG. 20E. In FIG. 20E, n EL layers (EL layer 786(1) to EL layer 786(n)) are provided between the conductor 772 and the conductor 788, and a tandem-structured light-emitting device 572 having a charge generation layer 792 is shown between each of the EL layers 786. Here, the EL layer 786(1) to the EL layer 786(n) can have the same configuration as the EL layer 786 shown in FIG. 20B. Note that FIG. 20E shows the EL layer 786(1), the EL layer 786(m), and the EL layer 786(n) among the EL layers 786. Here, m is an integer of 2 or more and less than n, and n is an integer of m or more. The larger the value of n, the higher the current efficiency and the external quantum efficiency of the light-emitting device 572 can be. Therefore, a high-brightness image can be displayed on the display device 100. Further, the power consumption of the display device 100 can be reduced.

[0284] The constituent materials that can be used for the light-emitting device 572 will be described.

[0285] 〔Conductors 772 and 788〕 For the conductors 772 and 788, as long as the functions of the anode and cathode can be satisfied, the materials shown below can be appropriately combined and used. For example, metals, alloys, electrically conductive compounds, and mixtures thereof can be appropriately used. Specifically, indium-tin oxide (also referred to as ITO), indium-silicon-tin oxide (also referred to as ITSO), indium-zinc oxide, indium-tungsten-zinc oxide can be mentioned. In addition, metals such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), neodymium (Nd), etc., and alloys containing these appropriately combined can also be used. In addition, elements belonging to Group 1 or Group 2 of the periodic table not exemplified above (for example, lithium (Li), cesium (Cs), calcium (Ca), strontium (Sr)), rare earth metals such as europium (Eu), ytterbium (Yb), and alloys containing these appropriately combined, and other graphene, etc. can be used.

[0286] 〔Hole injection layer 721 and hole transport layer 722〕 The hole injection layer 721 is a layer that injects holes from the conductor 772 which is the anode or the charge generation layer 792 into the EL layer 786, and is a layer containing a material with high hole injection properties. Here, the EL layer 786 is assumed to include the EL layer 786a, the EL layer 786b, the EL layer 786c, and the EL layers 786(1) to 786(n).

[0287] Examples of materials with high hole injection properties include transition metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. In addition, phthalocyanine-based compounds, aromatic amine compounds, or polymers can be used.

[0288] As a material with high hole injection property, a composite material containing a hole transporting material and an acceptor material (electron accepting material) can also be used. In this case, electrons are drawn from the hole transporting material by the acceptor material, and holes are generated in the hole injection layer 721. Then, the holes are injected into the light emitting layer 723 through the hole transporting layer 722. Note that the hole injection layer 721 may be formed as a single layer made of a composite material containing a hole transporting material and an acceptor material (electron accepting material), or may be formed by laminating the hole transporting material and the acceptor material (electron accepting material) as separate layers.

[0289] The hole transporting layer 722 is a layer that transports the holes injected from the conductor 772 to the light emitting layer 723 by the hole injection layer 721. Note that the hole transporting layer 722 is a layer containing a hole transporting material. It is preferable to use a hole transporting material for the hole transporting layer 722 that has a HOMO level that is the same as or close to the HOMO level of the hole injection layer 721.

[0290] As the acceptor material used for the hole injection layer 721, metal oxides belonging to Groups 4 to 8 in the periodic table can be used. Specifically, molybdenum oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, tungsten oxide, manganese oxide, and rhenium oxide can be mentioned. Among them, molybdenum oxide is particularly preferable because it is stable in the air, has low hygroscopicity, and is easy to handle. In addition, organic acceptors such as quinodimethane derivatives, chloranil derivatives, and hexaazatriphenylene derivatives can be used.

[0291] The hole transporting material used for the hole injection layer 721 and the hole transporting layer 722 preferably has a hole mobility of 10 -6 cm 2 / Vs or more. Note that as long as the material has higher hole transportability than electrons, materials other than these can be used.

[0292] As the hole transporting material, π-electron excessive heteroaromatic compounds (such as carbazole derivatives and indole derivatives) and aromatic amine compounds are preferred.

[0293] However, the hole transporting material is not limited to the above, and various known materials can be used alone or in combination of one or more kinds as the hole transporting material for the hole injection layer 721 and the hole transport layer 722. Note that the hole transport layer 722 may be formed of a plurality of layers respectively. That is, for example, a first hole transport layer and a second hole transport layer may be laminated.

[0294] 〔Light-emitting layer 723〕 The light-emitting layer 723 is a layer containing a light-emitting substance. As the light-emitting substance, substances exhibiting light-emitting colors such as blue, purple, blue-violet, green, yellow-green, yellow, orange, and red are appropriately used. Here, as shown in FIGS. 20C, 20D, and 20E, when the light-emitting device 572 has a plurality of EL layers, by using different light-emitting substances for the light-emitting layers 723 provided in each EL layer, a configuration exhibiting different light-emitting colors (for example, white light emission obtained by combining light-emitting colors in a complementary color relationship) can be achieved. For example, when the light-emitting device 572 has the configuration shown in FIG. 20C, by making the light-emitting substance used in the light-emitting layer 723 provided in the EL layer 786a different from the light-emitting substance used in the light-emitting layer 723 provided in the EL layer 786b, the light-emitting color exhibited by the EL layer 786a and the light-emitting color exhibited by the EL layer 786b can be made different. Note that one light-emitting layer may have a laminated structure having different light-emitting substances.

[0295] In addition to the light-emitting substance (guest material), the light-emitting layer 723 may have one or more organic compounds (host material, assist material). Further, as the one or more organic compounds, one or both of a hole transporting material and an electron transporting material can be used.

[0296] The luminescent material that can be used in the light-emitting layer 723 is not particularly limited, and a luminescent material that converts singlet excitation energy into light emission in the visible light region or a luminescent material that converts triplet excitation energy into light emission in the visible light region can be used. Examples of the above luminescent materials include the following.

[0297] Examples of the luminescent material that converts singlet excitation energy into light emission include substances that emit fluorescence (fluorescent materials), such as pyrene derivatives, anthracene derivatives, triphenylene derivatives, fluorene derivatives, carbazole derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, dibenzoquinoxaline derivatives, quinoxaline derivatives, pyridine derivatives, pyrimidine derivatives, phenanthrene derivatives, naphthalene derivatives, etc. In particular, pyrene derivatives are preferred because of their high luminescence quantum yield.

[0298] Examples of the luminescent material that converts triplet excitation energy into light emission include substances that emit phosphorescence (phosphorescent materials) and thermally activated delayed fluorescence (TADF: Thermally activated delayed fluorescence) materials that exhibit thermally activated delayed fluorescence.

[0299] Examples of the phosphorescent materials include organometallic complexes, metal complexes (platinum complexes), rare earth metal complexes, etc. Since these exhibit different emission colors (emission peaks) for each substance, they are appropriately selected and used as needed.

[0300] For the blue luminescent material, a substance with a photoluminescence peak wavelength of 430 nm or more and 470 nm or less, more preferably 430 nm or more and 460 nm or less, can be used. For the green luminescent material, a substance with a photoluminescence peak wavelength of 500 nm or more and 540 nm or less, more preferably 500 nm or more and 530 nm or less, can be used. For the red luminescent material, a substance with a photoluminescence peak wavelength of 610 nm or more and 680 nm or less, more preferably 620 nm or more and 680 nm or less, can be used. Note that the photoluminescence measurement can be performed on either a solution or a thin film.

[0301] By using such a compound in combination with the microcavity effect, the above-described chromaticity can be achieved more easily. At this time, the film thickness of the semi-transmissive / semi-reflective electrode (metal thin film portion) required to obtain the microcavity effect is preferably 20 nm or more and 40 nm or less. More preferably, it is greater than 25 nm and 40 nm or less. Note that if it exceeds 40 nm, the efficiency may decrease.

[0302] As the organic compound (host material, assist material) used in the light-emitting layer 723, a substance having an energy gap larger than the energy gap of the light-emitting substance (guest material) may be selected and used singly or in combination of two or more. Note that the above-described hole-transporting material and the electron-transporting material described later can also be used as the host material or the assist material, respectively.

[0303] When the light-emitting substance is a fluorescent material, it is preferable to use an organic compound having a large energy level of the singlet excited state and a small energy level of the triplet excited state as the host material. For example, it is preferable to use an anthracene derivative or a tetracene derivative.

[0304] When the light-emitting substance is a phosphorescent material, an organic compound having a triplet excitation energy larger than the triplet excitation energy (energy difference between the ground state and the triplet excited state) of the light-emitting substance may be selected as the host material. In this case, in addition to zinc or aluminum-based metal complexes, oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, pyrimidine derivatives, triazine derivatives, pyridine derivatives, bipyridine derivatives, phenanthroline derivatives, etc., aromatic amines, carbazole derivatives, etc. can also be used.

[0305] When a plurality of organic compounds are used in the light-emitting layer 723, it is preferable to use a compound that forms an exciplex by mixing it with a light-emitting substance. In this case, various organic compounds can be used in appropriate combinations. However, in order to efficiently form an exciplex, it is particularly preferable to combine a compound that easily accepts holes (hole-transporting material) and a compound that easily accepts electrons (electron-transporting material). Specific examples of the hole-transporting material and the electron-transporting material can be the materials shown in this embodiment mode.

[0306] A TADF material is a material in which an up-conversion (reverse intersystem crossing) from a triplet excited state to a singlet excited state is possible by slight thermal energy and which efficiently exhibits light emission (fluorescence) from the singlet excited state. Further, as conditions for efficiently obtaining thermally activated delayed fluorescence, the energy difference between the triplet excitation level and the singlet excitation level is 0 eV or more and 0.2 eV or less, preferably 0 eV or more and 0.1 eV or less. Further, the delayed fluorescence in a TADF material refers to light emission having a spectrum similar to that of normal fluorescence but having a significantly long lifetime. The lifetime is -6 seconds or more, preferably -3 seconds or more.

[0307] Examples of the TADF material include fullerenes and their derivatives, acridine derivatives such as proflavine, and eosin. Further, metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) etc. can be mentioned.

[0308] In addition, heterocyclic compounds having a π-electron-excessive heteroaromatic ring and a π-electron-deficient heteroaromatic ring can be used. Note that a substance in which a π-electron-excessive heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded is particularly preferable because both the donor property of the π-electron-excessive heteroaromatic ring and the acceptor property of the π-electron-deficient heteroaromatic ring become strong and the energy difference between the singlet excited state and the triplet excited state becomes small.

[0309] In addition, when using a TADF material, it can also be used in combination with other organic compounds.

[0310] 〔Electron transport layer 724〕 The electron transport layer 724 is a layer that transports electrons injected from the conductor 788 to the light-emitting layer 723 by the electron injection layer 725. Note that the electron transport layer 724 is a layer containing an electron-transporting material. The electron-transporting material used for the electron transport layer 724 is preferably a substance having an electron mobility of 1×10 -6 cm 2 / Vs or more. Note that, as long as it is a substance with higher electron transportability than holes, other substances can be used.

[0311] Examples of the electron-transporting material include metal complexes having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, pyridine derivatives, bipyridine derivatives, etc. In addition, π-electron-deficient heteroaromatic compounds such as nitrogen-containing heteroaromatic compounds can also be used.

[0312] The electron transport layer 724 may not only be a single layer, but may also have a structure in which two or more layers composed of the above substances are laminated.

[0313] 〔Electron injection layer 725〕 The electron injection layer 725 is a layer containing a substance with high electron injection properties. For the electron injection layer 725, alkali metals, alkaline earth metals, or their compounds such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), lithium oxide (LiO x ) etc. can be used. In addition, rare earth metal compounds such as erbium fluoride (ErF3) can be used. Also, electride may be used for the electron injection layer 725. Examples of electride include substances obtained by adding electrons at a high concentration to a mixed oxide of calcium and aluminum. Note that the substances constituting the above-described electron transport layer 724 can also be used.

[0314] A composite material formed by mixing an organic compound and an electron donor may be used for the electron injection layer 725. Since electrons are generated in the organic compound by the electron donor in such a composite material, it has excellent electron injection properties and electron transport properties. In this case, as the organic compound, it is preferably a material excellent in transporting the generated electrons. Specifically, for example, an electron transport material (such as a metal complex or a heteroaromatic compound) used for the above-described electron transport layer 724 can be used. As the electron donor, any substance that exhibits electron-donating properties to the organic compound may be used. Specifically, an alkali metal, an alkaline earth metal, or a rare earth metal is preferable, and examples include lithium, cesium, magnesium, calcium, erbium, ytterbium, etc. Also, an alkali metal oxide or an alkaline earth metal oxide is preferable, and examples include lithium oxide, calcium oxide, barium oxide, etc. Also, a Lewis base such as magnesium oxide can be used. Also, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can be used.

[0315] [Charge generation layer 792] When a voltage is applied between the conductor 772 and the conductor 788, the charge generation layer 792 has a function of injecting electrons into the EL layer 786 on the side closer to the conductor 772 and injecting holes into the EL layer 786 on the side opposite to the conductor 788 among the two EL layers 786 in contact with the charge generation layer 792. For example, in the light-emitting device 572 having the configuration shown in FIG. 20C, the charge generation layer 792 has a function of injecting electrons into the EL layer 786a and injecting holes into the EL layer 786b. Note that the charge generation layer 792 may have a configuration in which an electron acceptor is added to a hole transport material, or a configuration in which an electron donor is added to an electron transport material. Also, both of these configurations may be laminated. By forming the charge generation layer 792 using the above-described materials, an increase in the driving voltage of the display device 100 when the EL layers are laminated can be suppressed.

[0316] In the charge generation layer 792, when the configuration is such that an electron acceptor is added to the hole transporting material, examples of the electron acceptor include 7,7,8,8 - tetracyano - 2,3,5,6 - tetrafluoroquinodimethane (abbreviation: F4 - TCNQ), chloranil, etc. Also, metal oxides belonging to Groups 4 to 8 in the periodic table of elements can be mentioned. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, etc. can be given.

[0317] In the charge generation layer 792, when the configuration is such that an electron donor is added to the electron transporting material, as the electron donor, an alkali metal, an alkaline earth metal, a rare earth metal, a metal belonging to Groups 2 and 13 in the periodic table of elements, and their oxides and carbonates can be used. Specifically, it is preferable to use lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesium carbonate, etc. Also, an organic compound such as tetrathianaphthacene may be used as the electron donor.

[0318] Note that for the fabrication of the light - emitting device 572, a vacuum process such as a vapor deposition method or a solution process such as a spin - coating method or an ink - jet method can be used. When using the vapor deposition method, a physical vapor deposition method (PVD method) such as a sputtering method, an ion plating method, an ion beam vapor deposition method, a molecular beam vapor deposition method, a vacuum vapor deposition method, etc., or a chemical vapor deposition method (CVD method) etc. can be used. In particular, for the functional layers (hole injection layer, hole transport layer, light - emitting layer, electron transport layer, electron injection layer) and the charge generation layer included in the EL layer of the light - emitting device, they can be formed by methods such as a vapor deposition method (vacuum vapor deposition method etc.), a coating method (dip - coating method, die - coating method, bar - coating method, spin - coating method, spray - coating method etc.), a printing method (ink - jet method, screen (stencil printing) method, offset (lithographic printing) method, flexo (letterpress printing) method, gravure method, micro - contact method etc.).

[0319] Note that each functional layer (hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer) and charge generation layer that make up the EL layer of the light-emitting device shown in this embodiment are not limited to the materials described above, and other materials can be used in combination as long as they can satisfy the functions of each layer. As an example, polymer compounds (oligomers, dendrimers, polymers, etc.), medium molecular compounds (compounds in the intermediate region between low molecules and polymers: molecular weight 400 to 4000), inorganic compounds (quantum dot materials, etc.) can be used. Note that as the quantum dot material, colloidal quantum dot materials, alloy-type quantum dot materials, core-shell type quantum dot materials, core-type quantum dot materials, etc. can be used.

[0320] The configuration examples illustrated in this embodiment, and the corresponding drawings, etc. can be implemented by appropriately combining at least a part of them with other configuration examples, drawings, etc.

[0321] This embodiment can be implemented by appropriately combining at least a part of it with other embodiments described in this specification.

[0322] (Embodiment 2) In this embodiment, a transistor that can be used for a display device which is one aspect of the present invention will be described.

[0323] <Configuration Example 1 of Transistor> FIGS. 21A, 21B, and 21C are top views and cross-sectional views of a transistor 200A that can be used for a display device which is one aspect of the present invention, and the periphery of the transistor 200A. The transistor 200A can be applied to a display device of one aspect of the present invention.

[0324] FIG. 21A is a top view of transistor 200A. FIGS. 21B and 21C are cross-sectional views of transistor 200A. Here, FIG. 21B is a cross-sectional view of the portion indicated by the dashed line A1 - A2 in FIG. 21A, and is also a cross-sectional view in the channel length direction of transistor 200A. Further, FIG. 21C is a cross-sectional view of the portion indicated by the dashed line A3 - A4 in FIG. 21A, and is also a cross-sectional view in the channel width direction of transistor 200A. Note that in the top view of FIG. 21A, some elements are omitted for clarity of the drawing.

[0325] As shown in FIG. 21, transistor 200A includes a metal oxide 230a disposed on a substrate (not shown), a metal oxide 230b disposed on the metal oxide 230a, conductors 242a and 242b disposed spaced apart from each other on the metal oxide 230b, an insulator 280 disposed on the conductors 242a and 242b with an opening formed between the conductors 242a and 242b, a conductor 260 disposed in the opening, an insulator 250 disposed between the metal oxide 230b, the conductors 242a, 242b, and the insulator 280 and the conductor 260, and a metal oxide 230c disposed between the metal oxide 230b, the conductors 242a, 242b, and the insulator 280 and the insulator 250. Here, as shown in FIGS. 21B and 21C, it is preferable that the upper surface of the conductor 260 substantially coincides with the upper surfaces of the insulator 250, the insulator 254, the metal oxide 230c, and the insulator 280. In the following, the metal oxides 230a, 230b, and 230c may be collectively referred to as the metal oxide 230. Also, the conductors 242a and 242b may be collectively referred to as the conductor 242.

[0326] In the transistor 200A shown in FIG. 21, the side surfaces of the conductor 242a and the conductor 242b on the side of the conductor 260 have a substantially perpendicular shape. Note that the transistor 200A shown in FIG. 21 is not limited to this, and the angle formed by the side surface and the bottom surface of the conductor 242a and the conductor 242b may be 10° or more and 80° or less, preferably 30° or more and 60° or less. Further, the opposing side surfaces of the conductor 242a and the conductor 242b may have a plurality of surfaces.

[0327] As shown in FIG. 21, it is preferable that the insulator 254 is disposed between the insulator 224, the metal oxides 230a, 230b, the conductors 242a, 242b, and the metal oxide 230c, and the insulator 280. Here, as shown in FIGS. 21B and 21C, the insulator 254 preferably contacts the side surface of the metal oxide 230c, the upper surface and the side surface of the conductor 242a, the upper surface and the side surface of the conductor 242b, the side surfaces of the metal oxides 230a and 230b, and the upper surface of the insulator 224.

[0328] Note that in the transistor 200A, a configuration in which three layers of the metal oxides 230a, 230b, and 230c are stacked in a region where a channel is formed (hereinafter also referred to as a channel formation region) and in the vicinity thereof is shown, but the present invention is not limited to this. For example, a two-layer structure of the metal oxides 230b and 230c or a stacked structure of four or more layers may be provided. Further, in the transistor 200A, the conductor 260 is shown as a two-layer stacked structure, but the present invention is not limited to this. For example, the conductor 260 may have a single-layer structure or a stacked structure of three or more layers. Further, each of the metal oxides 230a, 230b, and 230c may have a stacked structure of two or more layers.

[0329] For example, when the metal oxide 230c has a stacked structure including a first metal oxide and a second metal oxide on the first metal oxide, the first metal oxide preferably has the same composition as the metal oxide 230b, and the second metal oxide preferably has the same composition as the metal oxide 230a.

[0330] Here, the conductor 260 functions as the gate electrode of the transistor, and the conductors 242a and 242b function as the source electrode or the drain electrode, respectively. As described above, the conductor 260 is formed so as to be embedded in the opening of the insulator 280 and the region sandwiched between the conductors 242a and 242b. Here, the arrangement of the conductor 260, the conductor 242a, and the conductor 242b is self-alignedly selected with respect to the opening of the insulator 280. That is, in the transistor 200A, the gate electrode can be self-alignedly arranged between the source electrode and the drain electrode. Therefore, since the conductor 260 can be formed without providing an alignment margin, the occupied area of the transistor 200A can be reduced. As a result, the display device can be made high-definition. In addition, the display device can have a narrow bezel.

[0331] As shown in FIG. 21, the conductor 260 preferably has a conductor 260a provided inside the insulator 250 and a conductor 260b provided so as to be embedded inside the conductor 260a.

[0332] The transistor 200A preferably has an insulator 214 disposed on a substrate (not shown), an insulator 216 disposed on the insulator 214, a conductor 205 disposed so as to be embedded in the insulator 216, an insulator 222 disposed on the insulator 216 and the conductor 205, and an insulator 224 disposed on the insulator 222. Preferably, a metal oxide 230a is disposed on the insulator 224.

[0333] Preferably, an insulator 274 functioning as an interlayer film and an insulator 281 are disposed on the transistor 200A. Here, the insulator 274 is preferably disposed in contact with the upper surfaces of the conductor 260, the insulator 250, the insulator 254, the metal oxide 230c, and the insulator 280.

[0334] The insulator 222, the insulator 254, and the insulator 274 preferably have a function of suppressing the diffusion of at least one of hydrogen (e.g., hydrogen atoms, hydrogen molecules, etc.). For example, the insulator 222, the insulator 254, and the insulator 274 preferably have lower hydrogen permeability than the insulator 224, the insulator 250, and the insulator 280. Further, the insulator 222 and the insulator 254 preferably have a function of suppressing the diffusion of at least one of oxygen (e.g., oxygen atoms, oxygen molecules, etc.). For example, the insulator 222 and the insulator 254 preferably have lower oxygen permeability than the insulator 224, the insulator 250, and the insulator 280.

[0335] Here, the insulator 224, the metal oxide 230, and the insulator 250 are separated from the insulator 280 and the insulator 281 by the insulator 254 and the insulator 274. Therefore, it is possible to suppress impurities such as hydrogen contained in the insulator 280 and the insulator 281 and excessive oxygen from mixing into the insulator 224, the metal oxide 230a, the metal oxide 230b, and the insulator 250.

[0336] A conductor 240 (conductor 240a and conductor 240b) that is electrically connected to the transistor 200A and functions as a plug is preferably provided. An insulator 241 (insulator 241a and insulator 241b) is provided in contact with the side surface of the conductor 240 that functions as a plug. That is, the insulator 241 is provided in contact with the inner walls of the openings of the insulator 254, the insulator 280, the insulator 274, and the insulator 281. Further, a first conductor of the conductor 240 may be provided in contact with the side surface of the insulator 241, and a second conductor of the conductor 240 may be provided further inside. Here, the height of the upper surface of the conductor 240 and the height of the upper surface of the insulator 281 can be made approximately the same. In the transistor 200A, a configuration in which the first conductor of the conductor 240 and the second conductor of the conductor 240 are laminated is shown, but the present invention is not limited to this. For example, the conductor 240 may be provided as a single layer or a laminated structure of three or more layers. When the structure has a laminated structure, ordinal numbers may be assigned in the order of formation for distinction.

[0337] For the transistor 200A, it is preferable to use, as the metal oxide 230 (metal oxides 230a, 230b, and 230c) including a channel formation region, a metal oxide that functions as an oxide semiconductor (hereinafter, also referred to as an oxide semiconductor). For example, as the metal oxide that becomes the channel formation region of the metal oxide 230, it is preferable to use one having a bandgap of 2 eV or more, preferably 2.5 eV or more.

[0338] The above metal oxide preferably contains at least indium (In) or zinc (Zn). In particular, it preferably contains indium (In) and zinc (Zn). In addition to these, it is preferable that the element M is contained. As the element M, one or more of aluminum (Al), gallium (Ga), yttrium (Y), tin (Sn), boron (B), titanium (Ti), iron (Fe), nickel (Ni), germanium (Ge), zirconium (Zr), molybdenum (Mo), lanthanum (La), cerium (Ce), neodymium (Nd), hafnium (Hf), tantalum (Ta), tungsten (W), magnesium (Mg), or cobalt (Co) can be used. In particular, the element M is preferably one or more of aluminum (Al), gallium (Ga), yttrium (Y), or tin (Sn). Further, it is more preferable that the element M has either or both of Ga and Sn.

[0339] Also, as shown in FIG. 21B, the film thickness of the region where the metal oxide 230b does not overlap with the conductor 242 may be thinner than the film thickness of the region where the metal oxide 230b overlaps with the conductor 242. This is formed by removing a part of the upper surface of the metal oxide 230b when forming the conductors 242a and 242b. When a conductive film that becomes the conductor 242 is formed on the upper surface of the metal oxide 230b, a region with low resistance may be formed in the vicinity of the interface with the conductive film. In this way, by removing the region with low resistance located between the conductors 242a and 242b on the upper surface of the metal oxide 230b, it is possible to prevent a channel from being formed in the region.

[0340] According to one aspect of the present invention, a display device having small-sized transistors and high definition can be provided. Alternatively, a display device having transistors with large on-currents and high brightness can be provided. Alternatively, a display device having fast-operating transistors and fast operation can be provided. Alternatively, a display device having transistors with stable electrical characteristics and high reliability can be provided. Alternatively, a display device having transistors with small off-currents and low power consumption can be provided.

[0341] A detailed configuration of the transistor 200A that can be used in the display device according to one aspect of the present invention will be described.

[0342] The conductor 205 is arranged so as to have an overlapping region with the metal oxide 230 and the conductor 260. Further, the conductor 205 is preferably provided by being embedded in the insulator 216. Here, it is preferable to improve the flatness of the upper surface of the conductor 205. For example, the average surface roughness (Ra) of the upper surface of the conductor 205 may be 1 nm or less, preferably 0.5 nm or less, more preferably 0.3 nm or less. Thereby, the flatness of the insulator 224 formed on the conductor 205 can be improved, and the crystallinity of the metal oxides 230b and 230c can be improved.

[0343] Here, the conductor 260 may function as a first gate (also referred to as a top gate) electrode. Further, the conductor 205 may function as a second gate (also referred to as a bottom gate) electrode. In that case, by changing the potential applied to the conductor 205 independently without linking it to the potential applied to the conductor 260, the V of the transistor 200A th can be controlled. In particular, by applying a negative potential to the conductor 205, the V of the transistor 200A th can be made larger than 0 V, and the off-current can be made smaller. Therefore, applying a negative potential to the conductor 205 can make the drain current smaller when the potential applied to the conductor 260 is 0 V than when no potential is applied.

[0344] The conductor 205 may be provided to be larger than the channel formation region in the metal oxide 230. In particular, as shown in FIG. 21C, the conductor 205 preferably extends also in a region outside the end portion intersecting the channel width direction of the metal oxide 230. That is, outside the side surface in the channel width direction of the metal oxide 230, it is preferable that the conductor 205 and the conductor 260 overlap with each other via an insulator.

[0345] By having the above configuration, the channel formation region of the metal oxide 230 can be electrically surrounded by the electric field of the conductor 260 having the function as the first gate electrode and the electric field of the conductor 205 having the function as the second gate electrode.

[0346] As shown in FIG. 21C, the conductor 205 is extended to also function as a wiring. However, the present invention is not limited to this, and a configuration may be adopted in which a conductor functioning as a wiring is provided under the conductor 205.

[0347] It is preferable to use a conductive material mainly composed of tungsten, copper, or aluminum for the conductor 205. Although the conductor 205 is illustrated as a single layer, it may have a laminated structure. For example, it may be a laminate of titanium or titanium nitride and the above conductive material.

[0348] A conductor having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N2O, NO, NO2, etc.), and copper atoms (the above impurities are difficult to permeate) may be used under the conductor 205. Alternatively, it is preferable to use a conductor having a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) (the above oxygen is difficult to permeate). In the present specification, the function of suppressing the diffusion of impurities or oxygen means the function of suppressing the diffusion of any one or all of the above impurities or the above oxygen.

[0349] By using a conductor having a function of suppressing the diffusion of oxygen under the conductor 205, it is possible to suppress the oxidation of the conductor 205 and the decrease in conductivity. As the conductor having a function of suppressing the diffusion of oxygen, for example, it is preferable to use tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like. Therefore, as the first conductor of the conductor 205, the above conductive material may be used as a single layer or a laminate.

[0350] The insulator 214 preferably functions as a barrier insulating film that suppresses impurities such as water or hydrogen from mixing into the transistor 200A from the substrate side. Therefore, it is preferable to use an insulating material for the insulator 214 that has a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N2O, NO, NO2, etc.), and copper atoms (the above impurities are difficult to permeate). Or, it is preferable to use an insulating material that has a function of suppressing the diffusion of at least one of oxygen (for example, oxygen atoms, oxygen molecules, etc.) (the above oxygen is difficult to permeate).

[0351] For example, it is preferable to use aluminum oxide, silicon nitride, or the like as the insulator 214. Thereby, it is possible to suppress the diffusion of impurities such as water or hydrogen from the substrate side to the transistor 200A side rather than the insulator 214. Or, it is possible to suppress the diffusion of oxygen contained in the insulator 224 or the like to the substrate side rather than the insulator 214.

[0352] The insulators 216, 280, and 281 that function as interlayer films preferably have a lower dielectric constant than the insulator 214. By using a material with a low dielectric constant as the interlayer film, the parasitic capacitance generated between the wirings can be reduced. For example, as the insulators 216, 280, and 281, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide with fluorine added, silicon oxide with carbon added, silicon oxide with carbon and nitrogen added, or silicon oxide having pores may be appropriately used.

[0353] The insulators 222 and 224 have the function as a gate insulator.

[0354] Here, the insulator 224 in contact with the metal oxide 230 preferably desorbs oxygen by heating. In this specification, oxygen desorbed by heating may be referred to as excess oxygen. For example, the insulator 224 may be appropriately silicon oxide, silicon oxynitride, or the like. By providing an oxygen-containing insulator in contact with the metal oxide 230, oxygen vacancies in the metal oxide 230 can be reduced, and the reliability of the transistor 200A can be improved.

[0355] Specifically, as the insulator 224, it is preferable to use an oxide material in which some oxygen desorbs by heating. An oxide that desorbs oxygen by heating means that, in TDS (Thermal Desorption Spectroscopy) analysis, the desorption amount of oxygen in terms of oxygen atoms is 1.0×10 18 atoms / cm 3 or more, preferably 1.0×10 19 atoms / cm 3 or more, more preferably 2.0×10 19 atoms / cm 3 or more, or 3.0×10 20 atoms / cm 3 or more, and it is an oxide film. The surface temperature of the film during the above TDS analysis is preferably in the range of 100°C or more and 700°C or less, or 100°C or more and 400°C or less.

[0356] As shown in FIG. 21C, in the insulator 224, the film thickness of the region that does not overlap with the insulator 254 and does not overlap with the metal oxide 230b may be thinner than the film thickness of the other regions. In the insulator 224, the film thickness of the region that does not overlap with the insulator 254 and does not overlap with the metal oxide 230b is preferably a film thickness that allows sufficient diffusion of the above oxygen.

[0357] The insulator 222 preferably functions as a barrier insulating film that suppresses impurities such as water or hydrogen from mixing into the transistor 200A from the substrate side, similar to the insulator 214 and the like. For example, it is preferable that the insulator 222 has lower hydrogen permeability than the insulator 224. By surrounding the insulator 224, the metal oxide 230, the insulator 250, etc. with the insulator 222, the insulator 254, and the insulator 274, it is possible to suppress impurities such as water or hydrogen from entering the transistor 200A from the outside.

[0358] Furthermore, the insulator 222 preferably has a function of suppressing the diffusion of at least one of oxygen (for example, oxygen atoms, oxygen molecules, etc.) (the above oxygen is difficult to permeate). For example, it is preferable that the insulator 222 has lower oxygen permeability than the insulator 224. Since the insulator 222 has a function of suppressing the diffusion of oxygen and impurities, it is possible to reduce the diffusion of the oxygen contained in the metal oxide 230 to the substrate side, which is preferable. In addition, it is possible to suppress the reaction of the conductor 205 with the oxygen contained in the insulator 224 and the metal oxide 230.

[0359] As the insulator 222, an insulator containing one or both of oxides of aluminum and hafnium, which are insulating materials, may be used. As the insulator containing one or both of oxides of aluminum and hafnium, aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), etc. are preferably used. When the insulator 222 is formed using such a material, the insulator 222 functions as a layer that suppresses the release of oxygen from the metal oxide 230 and the mixing of impurities such as hydrogen from the peripheral portion of the transistor 200A into the metal oxide 230.

[0360] Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, zirconium oxide may be added to these insulators. Alternatively, these insulators may be nitrided. Silicon oxide, silicon oxynitride, or silicon nitride may be laminated on the above insulator and used.

[0361] The insulator 222 may be a single layer or a laminate of an insulator containing a so-called high-k material such as aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST). As the miniaturization and high integration of transistors progress, problems such as leakage current may occur due to the thinning of the gate insulator. By using a high-k material for the insulator that functions as the gate insulator, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness.

[0362] Note that the insulator 222 and the insulator 224 may have a laminated structure of two or more layers. In that case, it is not limited to a laminated structure made of the same material, and a laminated structure made of different materials may also be used. For example, a configuration may be adopted in which an insulator similar to the insulator 224 is provided under the insulator 222.

[0363] The metal oxide 230 has a metal oxide 230a, a metal oxide 230b on the metal oxide 230a, and a metal oxide 230c on the metal oxide 230b. By having the metal oxide 230a under the metal oxide 230b, diffusion of impurities from a structure formed below the metal oxide 230a to the metal oxide 230b can be suppressed. Also, by having the metal oxide 230c on the metal oxide 230b, diffusion of impurities from a structure formed above the metal oxide 230c to the metal oxide 230b can be suppressed.

[0364] Note that the metal oxide 230 preferably has a laminated structure of a plurality of oxide layers with different atomic number ratios of each metal atom. For example, when the metal oxide 230 contains at least indium (In) and element M, the ratio of the number of atoms of element M contained in the metal oxide 230a to the total number of atoms of all elements constituting the metal oxide 230a is preferably higher than the ratio of the number of atoms of element M contained in the metal oxide 230b to the total number of atoms of all elements constituting the metal oxide 230b. Further, the atomic number ratio of element M contained in the metal oxide 230a to In is preferably larger than the atomic number ratio of element M contained in the metal oxide 230b to In. Here, the metal oxide 230c can be a metal oxide that can be used for the metal oxide 230a or the metal oxide 230b.

[0365] It is preferable that the energy of the lower end of the conduction band of the metal oxides 230a and 230c is higher than the energy of the lower end of the conduction band of the metal oxide 230b. In other words, it is preferable that the electron affinity of the metal oxides 230a and 230c is smaller than the electron affinity of the metal oxide 230b. In this case, it is preferable to use the metal oxide 230c as the metal oxide that can be used for the metal oxide 230a. Specifically, the ratio of the number of atoms of element M contained in the metal oxide 230c to the total number of atoms of all elements constituting the metal oxide 230c is preferably higher than the ratio of the number of atoms of element M contained in the metal oxide 230b to the total number of atoms of all elements constituting the metal oxide 230b. Further, the atomic number ratio of element M contained in the metal oxide 230c to In is preferably larger than the atomic number ratio of element M contained in the metal oxide 230b to In.

[0366] Here, at the junction of the metal oxide 230a, the metal oxide 230b, and the metal oxide 230c, the energy level of the conduction band minimum changes gradually. In other words, it can be said that the energy level of the conduction band minimum at the junction of the metal oxide 230a, the metal oxide 230b, and the metal oxide 230c changes continuously or is continuously junctioned. To achieve this, it is preferable to reduce the defect level density of the mixed layer formed at the interface between the metal oxide 230a and the metal oxide 230b and the interface between the metal oxide 230b and the metal oxide 230c.

[0367] Specifically, the metal oxide 230a and the metal oxide 230b, and the metal oxide 230b and the metal oxide 230c have a common element other than oxygen (as a main component), so that a mixed layer with a low defect level density can be formed. For example, when the metal oxide 230b is an In-Ga-Zn oxide, the metal oxide 230a and the metal oxide 230c may be made of In-Ga-Zn oxide, Ga-Zn oxide, gallium oxide, or the like. The metal oxide 230c may also have a laminated structure. For example, a laminated structure of In-Ga-Zn oxide and Ga-Zn oxide on the In-Ga-Zn oxide, or a laminated structure of In-Ga-Zn oxide and gallium oxide on the In-Ga-Zn oxide can be used. In other words, a laminated structure of In-Ga-Zn oxide and an oxide not containing In may be used as the metal oxide 230c.

[0368] Specifically, as the metal oxide 230a, a metal oxide with an atomic ratio of In:Ga:Zn = 1:3:4 or 1:1:0.5 may be used. As the metal oxide 230b, a metal oxide with an atomic ratio of In:Ga:Zn = 4:2:3 or 3:1:2 may be used. As the metal oxide 230c, a metal oxide with an atomic ratio of In:Ga:Zn = 1:3:4, In:Ga:Zn = 4:2:3, Ga:Zn = 2:1, or Ga:Zn = 2:5 may be used. Further, as a specific example when the metal oxide 230c has a stacked structure, examples include a stacked structure of In:Ga:Zn = 4:2:3 and Ga:Zn = 2:1, a stacked structure of In:Ga:Zn = 4:2:3 and Ga:Zn = 2:5, a stacked structure of In:Ga:Zn = 4:2:3 and gallium oxide, etc.

[0369] At this time, the main path of the carriers becomes the metal oxide 230b. By configuring the metal oxide 230a and the metal oxide 230c as described above, the density of defect energy levels at the interface between the metal oxide 230a and the metal oxide 230b and at the interface between the metal oxide 230b and the metal oxide 230c can be reduced. Therefore, the influence of interface scattering on carrier conduction is reduced, and the transistor 200A can obtain a high on-current and high frequency characteristics. When the metal oxide 230c has a stacked structure, in addition to the effect of reducing the density of defect energy levels at the interface between the metal oxide 230b and the metal oxide 230c described above, it is expected to suppress the diffusion of the constituent elements of the metal oxide 230c toward the insulator 250 side. More specifically, since the metal oxide 230c has a stacked structure and an oxide containing no In is positioned above the stacked structure, the diffusion of In that can diffuse toward the insulator 250 side can be suppressed. Since the insulator 250 functions as a gate insulator, if In diffuses, the characteristics of the transistor deteriorate. Therefore, by forming the metal oxide 230c into a stacked structure, it becomes possible to provide a highly reliable display device.

[0370] On the metal oxide 230b, conductors 242 (conductor 242a and conductor 242b) that function as a source electrode and a drain electrode are provided. As the conductor 242, it is preferable to use 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, lanthanum, an alloy containing the above-described metal element as a component, or an alloy combining the above-described metal elements. For example, it is preferable to use tantalum nitride, titanium nitride, tungsten, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel, and the like. Further, tantalum nitride, titanium nitride, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel are preferable because they are conductive materials that are difficult to oxidize or materials that maintain conductivity even when absorbing oxygen.

[0371] By providing the conductor 242 so as to be in contact with the metal oxide 230, the oxygen concentration may be reduced in the vicinity of the conductor 242 of the metal oxide 230. Further, in the vicinity of the conductor 242 of the metal oxide 230, a metal compound layer containing the metal contained in the conductor 242 and the component of the metal oxide 230 may be formed. In such a case, in the region near the conductor 242 of the metal oxide 230, the carrier density increases, and the region becomes a low-resistance region.

[0372] Here, the region between the conductor 242a and the conductor 242b is formed to overlap the opening of the insulator 280. Thereby, the conductor 260 can be self-alignedly arranged between the conductor 242a and the conductor 242b.

[0373] The insulator 250 functions as a gate insulator. The insulator 250 is preferably disposed in contact with the upper surface of the metal oxide 230c. As the insulator 250, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide with fluorine added, silicon oxide with carbon added, silicon oxide with carbon and nitrogen added, and silicon oxide having pores can be used. In particular, silicon oxide and silicon oxynitride are preferable because they are stable against heat.

[0374] Similar to the insulator 224, it is preferable that the concentration of impurities such as water or hydrogen in the insulator 250 is reduced. The film thickness of the insulator 250 is preferably 1 nm or more and 20 nm or less.

[0375] A metal oxide may be provided between the insulator 250 and the conductor 260. The metal oxide preferably suppresses oxygen diffusion from the insulator 250 to the conductor 260. Thereby, oxidation of the conductor 260 by oxygen in the insulator 250 can be suppressed.

[0376] The metal oxide may function as part of the gate insulator. Therefore, when silicon oxide, silicon oxynitride, etc. are used for the insulator 250, it is preferable to use a metal oxide which is a high-k material having a high relative permittivity as the metal oxide. By forming the gate insulator into a laminated structure of the insulator 250 and the metal oxide, a laminated structure which is stable against heat and has a high relative permittivity can be obtained. Therefore, it is possible to reduce the gate potential applied during transistor operation while maintaining the physical film thickness of the gate insulator. Also, it is possible to thin the equivalent oxide thickness (EOT) of the insulator functioning as the gate insulator.

[0377] Specifically, a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, etc. can be used. In particular, it is preferable to use an insulator containing one or both of aluminum and hafnium oxides, such as aluminum oxide, hafnium oxide, and an oxide containing aluminum and hafnium (hafnium aluminate).

[0378] Although the conductor 260 is shown as a two-layer structure in FIG. 21, it may have a single-layer structure or a laminated structure of three or more layers.

[0379] For the conductor 260a, it is preferable to use a conductor having a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N2O, NO, NO2, etc.), and copper atoms as described above. Alternatively, it is preferable to use a conductive material having a function of suppressing the diffusion of at least one of oxygen (for example, oxygen atoms, oxygen molecules, etc.).

[0380] Since the conductor 260a has a function of suppressing the diffusion of oxygen, it is possible to suppress the oxidation of the conductor 260b by oxygen contained in the insulator 250 and the decrease in conductivity. As the conductive material having a function of suppressing the diffusion of oxygen, for example, tantalum, tantalum nitride, ruthenium, or ruthenium oxide is preferably used.

[0381] For the conductor 260b, it is preferable to use a conductive material mainly composed of tungsten, copper, or aluminum. In addition, since the conductor 260 also functions as a wiring, it is preferable to use a conductor having high conductivity. For example, a conductive material mainly composed of tungsten, copper, or aluminum can be used. Also, the conductor 260b may have a laminated structure, for example, a laminated structure of titanium or titanium nitride and the above conductive material.

[0382] As shown in FIGS. 21A and 21C, in a region that does not overlap with the conductor 242 of the metal oxide 230b, in other words, in the channel formation region of the metal oxide 230, the side surfaces of the metal oxide 230 are arranged to be covered by the conductor 260. Thereby, the electric field of the conductor 260 that functions as the first gate electrode is likely to act on the side surfaces of the metal oxide 230. Therefore, the on-current of the transistor 200A can be increased and the frequency characteristics can be improved.

[0383] Similar to the insulator 214 and the like, the insulator 254 preferably functions as a barrier insulating film that suppresses impurities such as water or hydrogen from entering the transistor 200A from the insulator 280 side. For example, the insulator 254 preferably has lower hydrogen permeability than the insulator 224. Further, as shown in FIGS. 21B and 21C, the insulator 254 preferably contacts the side surfaces of the metal oxide 230c, the upper and side surfaces of the conductor 242a, the upper and side surfaces of the conductor 242b, the side surfaces of the metal oxide 230a and the metal oxide 230b, and the upper surface of the insulator 224. With such a configuration, it is possible to suppress hydrogen contained in the insulator 280 from entering the metal oxide 230 from the upper or side surfaces of the conductor 242a, the conductor 242b, the metal oxide 230a, the metal oxide 230b, and the insulator 224.

[0384] Furthermore, the insulator 254 preferably has a function of suppressing the diffusion of at least one of oxygen (for example, oxygen atoms, oxygen molecules, etc.) (the above oxygen is difficult to permeate). For example, the insulator 254 preferably has lower oxygen permeability than the insulator 280 or the insulator 224.

[0385] The insulator 254 is preferably formed by a sputtering method. By forming the insulator 254 by a sputtering method in an atmosphere containing oxygen, oxygen can be added in the vicinity of the region where the insulator 254 of the insulator 224 is in contact. Thereby, oxygen can be supplied from the said area | region into the metal oxide 230 through the insulator 224. Here, since the insulator 254 has a function of suppressing the upward diffusion of oxygen, it is possible to prevent oxygen from diffusing from the metal oxide 230 to the insulator 280. In addition, since the insulator 222 has a function of suppressing the downward diffusion of oxygen, it is possible to prevent oxygen from diffusing from the metal oxide 230 to the substrate side. In this way, oxygen is supplied to the channel formation region of the metal oxide 230. Thereby, the oxygen deficiency of the metal oxide 230 can be reduced, and the normal ionization of the transistor can be suppressed.

[0386] As the insulator 254, for example, an insulator containing one or both of oxides of aluminum and hafnium may be formed. In addition, as the insulator containing one or both of oxides of aluminum and hafnium, it is preferable to use aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like.

[0387] By covering the insulator 224, the insulator 250, and the metal oxide 230 with the insulator 254 having a barrier property against hydrogen, the insulator 280 is separated from the insulator 224, the metal oxide 230, and the insulator 250 by the insulator 254. Thereby, since the intrusion of impurities, such as hydrogen, from the outside of the transistor 200A can be suppressed, favorable electrical characteristics and reliability can be given to the transistor 200A.

[0388] The insulator 280 is provided on the insulator 224, the metal oxide 230, and the conductor 242 via the insulator 254. For example, as the insulator 280, it is preferable to have silicon oxide, silicon oxynitride, silicon nitride oxide, silicon oxide added with fluorine, silicon oxide added with carbon, silicon oxide added with carbon and nitrogen, or silicon oxide having pores. In particular, silicon oxide and silicon oxynitride are preferable because they are thermally stable. In particular, materials such as silicon oxide, silicon oxynitride, and silicon oxide having pores are preferable because they can easily form a region containing oxygen that desorbs upon heating.

[0389] It is preferable that the concentration of impurities such as water or hydrogen in the insulator 280 is reduced. Also, the upper surface of the insulator 280 may be planarized.

[0390] Similar to the insulator 214 and the like, the insulator 274 preferably functions as a barrier insulating film that suppresses impurities such as water or hydrogen from mixing into the insulator 280 from above. As the insulator 274, for example, an insulator that can be used for the insulator 214, the insulator 254, etc. may be used.

[0391] It is preferable to provide an insulator 281 that functions as an interlayer film on the insulator 274. Similar to the insulator 224 and the like, it is preferable that the concentration of impurities such as water or hydrogen in the film of the insulator 281 is reduced.

[0392] The conductors 240a and 240b are disposed in the openings formed in the insulator 281, the insulator 274, the insulator 280, and the insulator 254. The conductors 240a and 240b are provided to face each other with the conductor 260 interposed therebetween. Note that the height of the upper surfaces of the conductors 240a and 240b may be on the same plane as the upper surface of the insulator 281.

[0393] In addition, an insulator 241a is provided in contact with the inner walls of the openings of the insulator 281, the insulator 274, the insulator 280, and the insulator 254, and a first conductor of the conductor 240a is formed in contact with the side surface thereof. The conductor 242a is located at least in part at the bottom of the opening, and the conductor 240a is in contact with the conductor 242a. Similarly, an insulator 241b is provided in contact with the inner walls of the openings of the insulator 281, the insulator 274, the insulator 280, and the insulator 254, and a first conductor of the conductor 240b is formed in contact with the side surface thereof. The conductor 242b is located at least in part at the bottom of the opening, and the conductor 240b is in contact with the conductor 242b.

[0394] It is preferable to use a conductive material mainly composed of tungsten, copper, or aluminum for the conductor 240a and the conductor 240b. Also, the conductor 240a and the conductor 240b may have a laminated structure.

[0395] When the conductor 240 has a laminated structure, for the conductors in contact with the metal oxide 230a, the metal oxide 230b, the conductor 242, the insulator 254, the insulator 280, the insulator 274, and the insulator 281, it is preferable to use a conductor having the function of suppressing the diffusion of impurities such as water or hydrogen as described above. For example, it is preferable to use tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, or ruthenium oxide. Also, the conductive material having the function of suppressing the diffusion of impurities such as water or hydrogen may be used in a single layer or in a laminated form. By using the conductive material, it is possible to prevent oxygen added to the insulator 280 from being absorbed by the conductor 240a and the conductor 240b. Also, it is possible to suppress impurities such as water or hydrogen from the upper layer of the insulator 281 from mixing into the metal oxide 230 through the conductor 240a and the conductor 240b.

[0396] As the insulators 241a and 241b, for example, insulators that can be used for the insulator 254 or the like may be used. Since the insulators 241a and 241b are provided in contact with the insulator 254, it is possible to suppress impurities such as water or hydrogen from the insulator 280 or the like from mixing into the metal oxide 230 through the conductors 240a and 240b. In addition, it is possible to prevent oxygen contained in the insulator 280 from being absorbed by the conductors 240a and 240b.

[0397] Although not shown, conductors that function as wiring may be arranged in contact with the upper surfaces of the conductor 240a and the conductor 240b. As the conductor that functions as wiring, it is preferable to use a conductive material mainly composed of tungsten, copper, or aluminum. Further, the conductor may have a laminated structure, for example, a laminate of titanium or titanium nitride and the above conductive material. The conductor may be formed so as to be embedded in an opening provided in the insulator.

[0398] <Example Configuration 2 of Transistor> FIGS. 22A, 22B, and 22C are top views and cross-sectional views of the transistor 200B that can be used in a display device according to an aspect of the present invention and the periphery of the transistor 200B. The transistor 200B is a modified example of the transistor 200A.

[0399] FIG. 22A is a top view of the transistor 200B. FIGS. 22B and 22C are cross-sectional views of the transistor 200B. Here, FIG. 22B is a cross-sectional view of the portion indicated by the one-dot chain line B1 - B2 in FIG. 22A, and is also a cross-sectional view in the channel length direction of the transistor 200B. FIG. 22C is a cross-sectional view of the portion indicated by the one-dot chain line B3 - B4 in FIG. 22A, and is also a cross-sectional view in the channel width direction of the transistor 200B. In the top view of FIG. 22A, some elements are omitted for clarity of the drawing.

[0400] In the transistor 200B, the conductor 242a and the conductor 242b have a region overlapping with the metal oxide 230c, the insulator 250, and the conductor 260. Thereby, the transistor 200B can be a transistor with a high on-current. Also, the transistor 200B can be a transistor that is easy to control.

[0401] The conductor 260 that functions as a gate electrode has the conductor 260a and the conductor 260b on the conductor 260a. It is preferable to use a conductive material for the conductor 260a that has a function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms. Alternatively, it is preferable to use a conductive material that has a function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.).

[0402] Since the conductor 260a has a function of suppressing the diffusion of oxygen, the material selectivity of the conductor 260b can be improved. That is, by having the conductor 260a, oxidation of the conductor 260b can be suppressed, and a decrease in conductivity can be prevented.

[0403] It is preferable to provide the insulator 254 so as to cover the upper surface and the side surface of the conductor 260, the side surface of the insulator 250, and the side surface of the metal oxide 230c. Note that the insulator 254 may be made of an insulating material that has a function of suppressing the diffusion of impurities such as water or hydrogen and oxygen.

[0404] By providing the insulator 254, oxidation of the conductor 260 can be suppressed. Also, by having the insulator 254, diffusion of impurities such as water and hydrogen that the insulator 280 has into the transistor 200B can be suppressed.

[0405] <Example Configuration 3 of Transistor> FIGS. 23A, 23B, and 23C are top views and cross-sectional views of the transistor 200C that can be used in a display device according to one aspect of the present invention, and the periphery of the transistor 200C. The transistor 200C is a modified example of the transistor 200A.

[0406] FIG. 23A is a top view of the transistor 200C. FIGS. 23B and 23C are cross-sectional views of the transistor 200C. Here, FIG. 23B is a cross-sectional view of the portion indicated by the dashed line C1-C2 in FIG. 23A, and is also a cross-sectional view in the channel length direction of the transistor 200C. FIG. 23C is a cross-sectional view of the portion indicated by the dashed line C3-C4 in FIG. 23A, and is also a cross-sectional view in the channel width direction of the transistor 200C. In the top view of FIG. 23A, some elements are omitted for clarity of the drawing.

[0407] In the transistor 200C, an insulator 250 is provided on the metal oxide 230c, and a metal oxide 252 is provided on the insulator 250. A conductor 260 is provided on the metal oxide 252, and an insulator 270 is provided on the conductor 260. An insulator 271 is provided on the insulator 270.

[0408] The metal oxide 252 preferably has a function of suppressing oxygen diffusion. By providing the metal oxide 252 that suppresses oxygen diffusion between the insulator 250 and the conductor 260, the diffusion of oxygen into the conductor 260 is suppressed. That is, it is possible to suppress a decrease in the amount of oxygen supplied to the metal oxide 230. In addition, oxidation of the conductor 260 by oxygen can be suppressed.

[0409] Note that the metal oxide 252 may have a function as part of the gate electrode. For example, an oxide semiconductor that can be used as the metal oxide 230 can be used as the metal oxide 252. In that case, by forming the conductor 260 by a sputtering method, the electrical resistance value of the metal oxide 252 can be reduced to make it a conductor. This can be called an OC (Oxide Conductor) electrode.

[0410] The metal oxide 252 may function as part of the gate insulator. Therefore, when using silicon oxide, silicon oxynitride, etc. for the insulator 250, it is preferable to use a metal oxide which is a high-k material with a high relative permittivity for the metal oxide 252. By adopting such a stacked structure, a stacked structure that is stable against heat and has a high relative permittivity can be obtained. Therefore, it becomes possible to reduce the gate potential applied during transistor operation while maintaining the physical film thickness. Also, it becomes possible to reduce the equivalent oxide thickness (EOT) of the insulating layer functioning as the gate insulator.

[0411] In the transistor 200C, the metal oxide 252 is shown as a single layer, but it may have a stacked structure of two or more layers. For example, a metal oxide functioning as part of the gate electrode and a metal oxide functioning as part of the gate insulator may be stacked and provided.

[0412] By having the metal oxide 252, when it functions as a gate electrode, it is possible to improve the on-current of the transistor 200C without weakening the influence of the electric field from the conductor 260. Or, when it functions as a gate insulator, by maintaining the distance between the conductor 260 and the metal oxide 230 due to the physical thickness of the insulator 250 and the metal oxide 252, the leakage current between the conductor 260 and the metal oxide 230 can be suppressed. Therefore, by providing a stacked structure of the insulator 250 and the metal oxide 252, the physical distance between the conductor 260 and the metal oxide 230 and the electric field strength applied from the conductor 260 to the metal oxide 230 can be easily adjusted.

[0413] Specifically, as the metal oxide 252, an oxide semiconductor with reduced resistance that can be used for the metal oxide 230 can be used. Or, a metal oxide containing one or two or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, or magnesium, etc. can be used.

[0414] In particular, it is preferable to use aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), etc., which are insulating layers containing one or both of aluminum and hafnium oxides. In particular, hafnium aluminate has higher heat resistance than a hafnium oxide film. Therefore, it is preferable because it is less likely to crystallize during the heat treatment in a later process. Note that the metal oxide 252 is not an essential component. It may be appropriately designed according to the required transistor characteristics.

[0415] The insulator 270 may be made of an insulating material having a function of suppressing the permeation of impurities such as water or hydrogen and oxygen. For example, it is preferable to use aluminum oxide or hafnium oxide or the like. Thereby, it is possible to suppress the oxidation of the conductor 260 by oxygen from above the insulator 270. Further, it is possible to suppress the mixing of impurities such as water or hydrogen from above the insulator 270 into the metal oxide 230 through the conductor 260 and the insulator 250.

[0416] The insulator 271 functions as a hard mask. By providing the insulator 271, when processing the conductor 260, the side surface of the conductor 260 can be made substantially vertical. Specifically, the angle formed by the side surface of the conductor 260 and the substrate surface can be 75 degrees or more and 100 degrees or less, preferably 80 degrees or more and 95 degrees or less.

[0417] Note that the insulator 271 may also function as a barrier layer by using an insulating material having a function of suppressing the permeation of impurities such as water or hydrogen and oxygen. In that case, the insulator 270 may not be provided.

[0418] By selectively removing a part of the insulator 270, the conductor 260, the metal oxide 252, the insulator 250, and the metal oxide 230c using the insulator 271 as a hard mask, these side surfaces can be made substantially coincident, and a part of the surface of the metal oxide 230b can be exposed.

[0419] Transistor 200C has regions 243a and 243b on a part of the exposed surface of metal oxide 230b. One of regions 243a or 243b functions as a source region, and the other of regions 243a or 243b functions as a drain region.

[0420] The formation of regions 243a and 243b can be realized, for example, by introducing impurity elements such as phosphorus or boron into the exposed surface of metal oxide 230b using an ion implantation method, an ion doping method, a plasma immersion ion implantation method, or a plasma treatment or the like. Note that in the present embodiment and the like, the "impurity element" refers to an element other than the main component element.

[0421] After exposing a part of the surface of metal oxide 230b, a metal film is formed, and then by performing a heat treatment, the elements contained in the metal film are diffused into metal oxide 230b to form regions 243a and 243b.

[0422] In the region where the impurity element of metal oxide 230b is introduced, the electrical resistivity decreases. Therefore, regions 243a and 243b may be referred to as "impurity regions" or "low resistance regions".

[0423] By using insulator 271 and / or conductor 260 as a mask, regions 243a and 243b can be formed in a self-aligned manner. Thus, regions 243a and / or 243b do not overlap with conductor 260, and the parasitic capacitance can be reduced. Also, no offset region is formed between the channel formation region and the source-drain region (regions 243a or 243b). By forming regions 243a and 243b in a self-aligned manner, an increase in the on-current, a reduction in the threshold voltage, an improvement in the operating frequency, etc. can be realized.

[0424] Transistor 200C has an insulator 272 on the side surfaces of an insulator 271, an insulator 270, a conductor 260, a metal oxide 252, an insulator 250, and a metal oxide 230c. The insulator 272 is preferably an insulator having a low relative permittivity. For example, it is preferably silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide with fluorine added, silicon oxide with carbon added, silicon oxide with carbon and nitrogen added, silicon oxide having pores, or a resin or the like. In particular, when silicon oxide, silicon oxynitride, silicon nitride oxide, or silicon oxide having pores is used for the insulator 272, it is preferable because an excess oxygen region can be easily formed in the insulator 272 in a later process. Further, silicon oxide and silicon oxynitride are preferable because they are thermally stable. Also, the insulator 272 preferably has a function of diffusing oxygen.

[0425] Note that in order to further reduce the off-current, an offset region may be provided between the channel formation region and the source / drain regions. The offset region is a region having a high electrical resistivity and is a region where the introduction of the above-described impurity elements is not performed. The formation of the offset region can be realized by introducing the above-described impurity elements after the formation of the insulator 272. In this case, the insulator 272 also functions as a mask similar to the insulator 271 and the like. Therefore, impurity elements are not introduced into the region overlapping the insulator 272 of the metal oxide 230b, and the electrical resistivity of the region can be kept high.

[0426] Transistor 200C has an insulator 254 on the insulator 272 and the metal oxide 230. The insulator 254 is preferably formed by a sputtering method. By using the sputtering method, an insulator with few impurities such as water or hydrogen can be formed.

[0427] Note that an oxide film formed by the sputtering method may extract hydrogen from the film formation target structure. Therefore, by the insulator 254 absorbing hydrogen and water from the metal oxide 230 and the insulator 272, the hydrogen concentration of the metal oxide 230 and the insulator 272 can be reduced.

[0428] <Constituent Materials of Transistor> The constituent materials that can be used for transistors will be described.

[0429] 〔Substrate〕 As the substrate for forming the transistor 200A, transistor 200B, or transistor 200C, for example, an insulator substrate, a semiconductor substrate, or a conductor substrate may be used. Examples of the insulator substrate include a glass substrate, a quartz substrate, a sapphire substrate, a stabilized zirconia substrate (such as yttria-stabilized zirconia substrate), a resin substrate, etc. Examples of the semiconductor substrate include semiconductor substrates such as silicon and germanium, or compound semiconductor substrates made of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, and gallium oxide. Furthermore, there are semiconductor substrates having an insulator region inside the aforementioned semiconductor substrates, such as SOI (Silicon On Insulator) substrates. Examples of the conductor substrate include a graphite substrate, a metal substrate, an alloy substrate, a conductive resin substrate, etc. Or, there are substrates having a metal nitride, substrates having a metal oxide, etc. Furthermore, there are substrates in which a conductor or a semiconductor is provided on an insulator substrate, substrates in which a conductor or an insulator is provided on a semiconductor substrate, substrates in which a semiconductor or an insulator is provided on a conductor substrate, etc. Or, those with elements provided on these substrates may also be used. Examples of the elements provided on the substrate include a capacitor element, a resistor element, a switch element, a light-emitting device, a memory element, etc.

[0430] 〔Insulator〕 Examples of the insulator include oxides, nitrides, oxynitrides, nitride oxides, metal oxides, metal oxynitrides, metal nitride oxides, etc. having insulating properties.

[0431] For example, as the miniaturization and high integration of transistors progress, problems such as leakage current may occur due to the thinning of the gate insulator. By using a high-k material for the insulator that functions as the gate insulator, it becomes possible to lower the voltage during transistor operation while maintaining the physical film thickness. On the other hand, for the insulator that functions as the interlayer film, by using a material with a low relative permittivity, the parasitic capacitance generated between the wirings can be reduced. Therefore, it is advisable to select a material according to the function of the insulator.

[0432] Examples of insulators with a high relative permittivity include gallium oxide, hafnium oxide, zirconium oxide, an oxide having aluminum and hafnium, a nitrogen oxide having aluminum and hafnium, an oxide having silicon and hafnium, a nitrogen oxide having silicon and hafnium, or a nitride having silicon and hafnium.

[0433] Examples of insulators with a low relative permittivity include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide with fluorine added, silicon oxide with carbon added, silicon oxide with carbon and nitrogen added, silicon oxide with pores, or resin.

[0434] A transistor using an oxide semiconductor can have its electrical characteristics stabilized by surrounding it with insulators (such as insulator 214, insulator 222, insulator 254, and insulator 274, etc.) that have a function of suppressing the permeation of impurities such as hydrogen and oxygen. As an insulator having a function of suppressing the permeation of impurities such as hydrogen and oxygen, for example, an insulator containing boron, carbon, nitrogen, oxygen, fluorine, magnesium, aluminum, silicon, phosphorus, chlorine, argon, gallium, germanium, yttrium, zirconium, lanthanum, neodymium, hafnium, or tantalum may be used in a single layer or in a laminated form. Specifically, as an insulator having a function of suppressing the permeation of impurities such as hydrogen and oxygen, metal oxides such as aluminum oxide, magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, or tantalum oxide, and metal nitrides such as aluminum nitride, aluminum titanium nitride, titanium nitride, silicon oxynitride, or silicon nitride can be used.

[0435] The insulator functioning as a gate insulator is preferably an insulator having a region containing oxygen that desorbs upon heating. For example, by forming a structure in which silicon oxide or silicon oxynitride having a region containing oxygen that desorbs upon heating is in contact with the metal oxide 230, the oxygen deficiency of the metal oxide 230 can be compensated.

[0436] 〔Conductor〕 As the conductor, it is preferable to use 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, lanthanum, etc., or an alloy containing the above-mentioned metal element as a component, or an alloy combining the above-mentioned metal elements. For example, it is preferable to use tantalum nitride, titanium nitride, tungsten, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel, etc. Further, tantalum nitride, titanium nitride, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, an oxide containing lanthanum and nickel are preferable because they are conductive materials that are difficult to oxidize or materials that maintain conductivity even when absorbing oxygen. Also, a semiconductor with high electrical conductivity typified by polycrystalline silicon containing impurity elements such as phosphorus, or a silicide such as nickel silicide may be used.

[0437] A plurality of conductors formed of the above materials may be laminated and used. For example, a laminated structure combining a material containing the above-mentioned metal element and a conductive material containing oxygen may be used. Also, a laminated structure combining a material containing the above-mentioned metal element and a conductive material containing nitrogen may be used. Also, a laminated structure combining a material containing the above-mentioned metal element, a conductive material containing oxygen, and a conductive material containing nitrogen may be used.

[0438] In addition, when using a metal oxide in the channel formation region of the transistor, for the conductor functioning as the gate electrode, it is preferable to use a laminated structure combining a material containing the above-mentioned metal element and a conductive material containing oxygen. In this case, it is advisable to provide the conductive material containing oxygen on the channel formation region side. By providing the conductive material containing oxygen on the channel formation region side, oxygen detached from the conductive material is easily supplied to the channel formation region.

[0439] In particular, as the conductor functioning as the gate electrode, it is preferable to use a conductive material containing a metal element and oxygen contained in the metal oxide in which the channel is formed. Further, a conductive material containing the above-described metal element and nitrogen may be used. For example, a conductive material containing nitrogen such as titanium nitride or tantalum nitride may be used. Further, 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, indium tin oxide added with silicon may be used. Further, indium gallium zinc oxide containing nitrogen may be used. By using such a material, it may be possible to capture hydrogen contained in the metal oxide in which the channel is formed. Or, it may be possible to capture hydrogen mixed from an external insulator or the like.

[0440] The configuration examples illustrated in the present embodiment, and the corresponding drawings and the like can be implemented by appropriately combining at least a part thereof with other configuration examples, drawings, etc.

[0441] This embodiment can be implemented by appropriately combining at least a part thereof with other embodiments described in this specification.

[0442] (Embodiment 3) In this embodiment, a metal oxide (hereinafter also referred to as an oxide semiconductor) that can be used for the OS transistor described in the above embodiment will be described.

[0443] <Classification of crystal structure> First, the classification of the crystal structure in the oxide semiconductor will be described with reference to FIG. 24A. FIG. 24A is a diagram for explaining the classification of the crystal structure of an oxide semiconductor, typically IGZO (a metal oxide containing In, Ga, and Zn).

[0444] As shown in FIG. 24A, oxide semiconductors are roughly classified into "Amorphous", "Crystalline", and "Crystal". Further, "Amorphous" includes completely amorphous. Further, "Crystalline" includes CAAC (c-axis-aligned crystalline), nc (nanocrystalline), and CAC (cloud-aligned composite). Note that single crystal, poly crystal, and completely amorphous are excluded from the classification of "Crystalline". Further, "Crystal" includes single crystal and poly crystal.

[0445] Note that the structure within the thick frame shown in FIG. 24A is an intermediate state between "Amorphous" and "Crystal", and belongs to a new boundary region (New crystalline phase). That is, the structure can be rephrased as an energetically unstable "Amorphous" or a structure completely different from "Crystal".

[0446] Note that the crystal structure of a film or a substrate can be evaluated using an X-ray diffraction (XRD) spectrum. Here, the XRD spectrum obtained by grazing-incidence XRD (GIXD) measurement of a CAAC-IGZO film classified as "Crystalline" is shown in FIG. 24B. Note that the GIXD method is also called the thin film method or the Seemann-Bohlin method. Hereinafter, the XRD spectrum obtained by the GIXD measurement shown in FIG. 24B will be simply referred to as the XRD spectrum. Note that the composition of the CAAC-IGZO film shown in FIG. 24B is in the vicinity of In:Ga:Zn = 4:2:3 [atomic ratio]. Also, the thickness of the CAAC-IGZO film shown in FIG. 24B is 500 nm.

[0447] As shown in FIG. 24B, in the XRD spectrum of the CAAC-IGZO film, peaks indicating clear crystallinity are detected. Specifically, in the XRD spectrum of the CAAC-IGZO film, a peak indicating c-axis orientation is detected near 2θ = 31°. As shown in FIG. 24B, the peak near 2θ = 31° is asymmetric about the angle at which the peak intensity is detected.

[0448] The crystal structure of the film or substrate can be evaluated by the diffraction pattern (also referred to as the nano-beam electron diffraction pattern) observed by the nano-beam electron diffraction method (NBED). The diffraction pattern of the CAAC-IGZO film is shown in FIG. 24C. FIG. 24C is a diffraction pattern observed by NBED in which the electron beam is incident parallel to the substrate. The composition of the CAAC-IGZO film shown in FIG. 24C is near In:Ga:Zn = 4:2:3 [atomic ratio]. In the nano-beam electron diffraction method, electron diffraction is performed with a probe diameter of 1 nm.

[0449] As shown in FIG. 24C, in the diffraction pattern of the CAAC-IGZO film, a plurality of spots indicating c-axis orientation are observed.

[0450] [Structure of Oxide Semiconductor] Note that when focusing on the crystal structure, the oxide semiconductor may be classified differently from that in FIG. 24A. For example, the oxide semiconductor can be divided into a single-crystalline oxide semiconductor and other non-single-crystalline oxide semiconductors. Examples of the non-single-crystalline oxide semiconductor include the above-mentioned CAAC-OS and nc-OS. The non-single-crystalline oxide semiconductor includes a polycrystalline oxide semiconductor, a pseudo-amorphous oxide semiconductor (a-like OS: amorphous-like oxide semiconductor), an amorphous oxide semiconductor, and the like.

[0451] Here, the details of the above-mentioned CAAC-OS, nc-OS, and a-like OS will be described.

[0452] [CAAC-OS] CAAC-OS is an oxide semiconductor having a plurality of crystal regions, and the c-axes of the plurality of crystal regions are oriented in a specific direction. Here, the specific direction means the thickness direction of the CAAC-OS film, the normal direction of the surface on which the CAAC-OS film is formed, or the normal direction of the surface of the CAAC-OS film. Also, the crystal region is a region having periodicity in the atomic arrangement. When the atomic arrangement is regarded as a lattice arrangement, the crystal region is also a region where the lattice arrangements are aligned. Further, CAAC-OS has a region where a plurality of crystal regions are connected in the a-b plane direction, and this region may have strain. Here, the strain refers to a portion where the orientation of the lattice arrangement changes between a region where the lattice arrangements are aligned and another region where the lattice arrangements are aligned in a region where a plurality of crystal regions are connected. That is, CAAC-OS is an oxide semiconductor in which the c-axis is oriented and there is no clear orientation in the a-b plane direction.

[0453] Each of the plurality of crystal regions is composed of one or a plurality of minute crystals (crystals having a maximum diameter of less than 10 nm). When a crystal region is composed of one minute crystal, the maximum diameter of the crystal region is less than 10 nm. Also, when a crystal region is composed of a number of minute crystals, the size of the crystal region may be about several tens of nm.

[0454] In an In-M-Zn oxide (the element M is one or more selected from aluminum, gallium, yttrium, tin, titanium, etc.), CAAC-OS tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium (In) and oxygen (hereinafter referred to as the In layer) and a layer containing the element M, zinc (Zn), and oxygen (hereinafter referred to as the (M,Zn) layer) are laminated. Here, indium and the element M are mutually substitutable. Therefore, the (M,Zn) layer may contain indium. Also, the In layer may contain the element M. Note that the In layer may also contain Zn. The layered structure is observed as a lattice image, for example, in a high-resolution TEM image.

[0455] When performing structural analysis on a CAAC-OS film using, for example, an XRD apparatus, in the out-of-plane XRD measurement using θ / 2θ scan, a peak indicating c-axis orientation is detected at 2θ = 31° or in its vicinity. Note that the position (the value of 2θ) of the peak indicating c-axis orientation may vary depending on the type, composition, etc. of the metal elements constituting CAAC-OS.

[0456] For example, in the electron diffraction pattern of a CAAC-OS film, a plurality of bright spots (spots) are observed. Note that one spot and another spot are observed at point-symmetric positions with the spot of the incident electron beam transmitted through the sample (also referred to as the direct spot) as the center of symmetry.

[0457] When observing the crystal region from the above specific direction, the lattice arrangement within the crystal region is based on a hexagonal lattice, but the unit cell is not necessarily a regular hexagon and may be a non-regular hexagon. Also, in the above distortion, there may be lattice arrangements such as pentagons and heptagons. Note that in CAAC-OS, even in the vicinity of the distortion, a clear grain boundary cannot be confirmed. That is, it can be seen that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is presumably because CAAC-OS can tolerate distortion due to the fact that the arrangement of oxygen atoms is not dense in the a-b plane direction and the interatomic bond distance changes due to the substitution of metal atoms.

[0458] Note that a crystal structure in which a clear grain boundary is confirmed is called a so-called polycrystal. Grain boundaries can become recombination centers and are likely to cause a decrease in the on-current of a transistor and a decrease in the field-effect mobility due to the capture of carriers. Therefore, CAAC-OS in which no clear grain boundary is confirmed is one of the crystalline oxides having a crystal structure suitable for the semiconductor layer of a transistor. Note that for forming CAAC-OS, a configuration having Zn is preferable. For example, In-Zn oxide and In-Ga-Zn oxide are preferable because they can suppress the generation of grain boundaries more than In oxide.

[0459] CAAC-OS is an oxide semiconductor with high crystallinity and no distinct crystal grain boundaries. Therefore, it can be said that in CAAC-OS, a decrease in electron mobility due to crystal grain boundaries is less likely to occur. Also, since the crystallinity of an oxide semiconductor may decrease due to impurity incorporation, defect generation, etc., CAAC-OS can also be said to be an oxide semiconductor with few impurities and defects (such as oxygen deficiencies). Therefore, the physical properties of the oxide semiconductor having CAAC-OS are stable. For this reason, the oxide semiconductor having CAAC-OS is heat-resistant and highly reliable. Also, CAAC-OS is stable against high temperatures (so-called thermal budget) in the manufacturing process. Therefore, when CAAC-OS is used for an OS transistor, it becomes possible to expand the degree of freedom in the manufacturing process.

[0460] [nc-OS] nc-OS has periodicity in the atomic arrangement in a minute region (for example, a region of 1 nm or more and 10 nm or less, particularly a region of 1 nm or more and 3 nm or less). In other words, nc-OS has minute crystals. Note that since the size of the minute crystals is, for example, 1 nm or more and 10 nm or less, particularly 1 nm or more and 3 nm or less, the minute crystals are also referred to as nano crystals. Also, nc-OS has no regularity in crystal orientation between different nano crystals. Therefore, no orientation is observed in the entire film. Therefore, depending on the analysis method, nc-OS may not be distinguishable from a-like OS or an amorphous oxide semiconductor. For example, when structural analysis is performed on an nc-OS film using an XRD apparatus, no peak indicating crystallinity is detected in the out-of-plane XRD measurement using θ / 2θ scan. Also, when electron beam diffraction (also referred to as limited field of view electron beam diffraction) using an electron beam with a probe diameter larger than that of the nano crystals (for example, 50 nm or more) is performed on the nc-OS film, a diffraction pattern such as a halo pattern is observed. On the other hand, when electron beam diffraction (also referred to as nano beam electron beam diffraction) using an electron beam with a probe diameter close to or smaller than that of the nano crystals (for example, 1 nm or more and 30 nm or less) is performed on the nc-OS film, an electron beam diffraction pattern in which a plurality of spots are observed in a ring-shaped region centered on a direct spot may be obtained.

[0461] [a-like OS] The a-like OS is an oxide semiconductor having a structure between the nc-OS and the amorphous oxide semiconductor. The a-like OS has a loose or low-density region. That is, the a-like OS has lower crystallinity compared to the nc-OS and the CAAC-OS. Also, the a-like OS has a higher hydrogen concentration in the film compared to the nc-OS and the CAAC-OS.

[0462] [Constitution of Oxide Semiconductor] Next, the details of the above-mentioned CAC-OS will be described. Note that the CAC-OS relates to the material constitution.

[0463] [CAC-OS] The CAC-OS is, for example, a constituent of a material in which the elements constituting the metal oxide are unevenly distributed in a size of 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 3 nm or less, or in the vicinity thereof. In the following, in the metal oxide, a state in which one or more metal elements are unevenly distributed and the regions having the metal elements are mixed in a size of 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 3 nm or less, or in the vicinity thereof is also referred to as a mosaic state or a patch state.

[0464] Furthermore, the CAC-OS becomes mosaic-like by separating the material into a first region and a second region, and the first region has a configuration distributed in the film (hereinafter also referred to as a cloud state). That is, the CAC-OS is a composite metal oxide having a configuration in which the first region and the second region are mixed.

[0465] Here, the atomic number ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In-Ga-Zn oxide are denoted as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS of the In-Ga-Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. Also, the second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Or, for example, the first region is a region where [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. Also, the second region is a region where [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

[0466] Specifically, the above-mentioned first region is a region mainly composed of indium oxide, indium zinc oxide, etc. Also, the above-mentioned second region is a region mainly composed of gallium oxide, gallium zinc oxide, etc. That is, the above-mentioned first region can be rephrased as a region mainly composed of In. Also, the above-mentioned second region can be rephrased as a region mainly composed of Ga.

[0467] Note that there may be cases where no clear boundary can be observed between the above-mentioned first region and the above-mentioned second region.

[0468] For example, in the CAC-OS of the In-Ga-Zn oxide, it can be confirmed by EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX) that the region mainly composed of In (the first region) and the region mainly composed of Ga (the second region) are unevenly distributed and have a mixed structure.

[0469] When CAC-OS is used in a transistor, the conductivity caused by the first region and the insulating property caused by the second region act complementarily, enabling the function of switching (turning on / off) to be imparted to CAC-OS. That is, CAC-OS has a conductive function in part of the material and an insulating function in part of the material, and has a function as a semiconductor in the whole material. By separating the conductive function and the insulating function, both functions can be enhanced to the maximum extent. Therefore, by using CAC-OS in a transistor, a high on-current (I on ), a high field-effect mobility (μ), and a good switching operation can be realized.

[0470] Oxide semiconductors have various structures and each has different characteristics. The oxide semiconductor according to one aspect of the present invention may have two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS.

[0471] <Transistor having an oxide semiconductor> Subsequently, the case of using the above oxide semiconductor in a transistor will be described.

[0472] By using the above oxide semiconductor in a transistor, a transistor with a high field-effect mobility can be realized. Also, a highly reliable transistor can be realized.

[0473] It is preferable to use an oxide semiconductor with a low carrier concentration in a transistor. For example, the carrier concentration of the oxide semiconductor is 1×10 17 cm -3 or less, preferably 1×10 15 cm -3 or less, more preferably 1×10 13 cm -3 or less, even more preferably 1×10 11 cm -3 or less, still more preferably 1×10 10 cm -3 less than, and 1×10 -9 cm-3 The above is the case. When reducing the carrier concentration of the oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be reduced and the density of defect levels may be reduced. In this specification and the like, the fact that the impurity concentration is low and the density of defect levels is low is referred to as high-purity intrinsic or substantially high-purity intrinsic. Note that an oxide semiconductor with a low carrier concentration may be referred to as a high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor.

[0474] Since the oxide semiconductor film having high-purity intrinsic or substantially high-purity intrinsic has a low density of defect levels, the density of trap levels may also be low.

[0475] The charge trapped in the trap levels of the oxide semiconductor takes a long time to disappear and may behave like a fixed charge. Therefore, a transistor in which a channel formation region is formed in an oxide semiconductor having a high trap level density may have unstable electrical characteristics.

[0476] Therefore, in order to stabilize the electrical characteristics of the transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. Further, in order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in the adjacent film. Examples of impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, silicon, and the like.

[0477] <Impurity> Here, the influence of each impurity in the oxide semiconductor will be described.

[0478] In an oxide semiconductor, when silicon or carbon, which is one of the Group 14 elements, is contained, defect levels are formed in the oxide semiconductor. Therefore, the concentration of silicon or carbon in the oxide semiconductor and the concentration of silicon or carbon near the interface with the oxide semiconductor (the concentration obtained by SIMS) are set to 2×10 18 atoms / cm 3 or less, preferably 2×10 17 atoms / cm 3 or less.

[0479] When an alkali metal or an alkaline earth metal is contained in an oxide semiconductor, defect levels may be formed and carriers may be generated. Therefore, a transistor using an oxide semiconductor containing an alkali metal or an alkaline earth metal tends to have normally-on characteristics. For this reason, the concentration of the alkali metal or alkaline earth metal in the oxide semiconductor obtained by SIMS is 1×10 18 atoms / cm 3 or less, preferably 2×10 16 atoms / cm 3 or less.

[0480] In an oxide semiconductor, when nitrogen is contained, electrons as carriers are generated, the carrier concentration increases, and it tends to be n-type. As a result, a transistor using an oxide semiconductor containing nitrogen as a semiconductor tends to have normally-on characteristics. Or, in an oxide semiconductor, when nitrogen is contained, trap levels may be formed. As a result, the electrical characteristics of the transistor may become unstable. For this reason, the nitrogen concentration in the oxide semiconductor obtained by SIMS is 5×10 19 atoms / cm 3 less, preferably 5×10 18 atoms / cm 3 or less, more preferably 1×10 18 atoms / cm 3 or less, even more preferably 5×10 17 atoms / cm 3 or less.

[0481] Hydrogen contained in the oxide semiconductor may react with oxygen bonded to a metal atom to form water, and thus oxygen deficiency may be formed. When hydrogen enters the oxygen deficiency, electrons as carriers may be generated. Also, a part of hydrogen may bond to oxygen bonded to a metal atom to generate electrons as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen tends to have normally-on characteristics. For this reason, it is preferable that hydrogen in the oxide semiconductor is reduced as much as possible. Specifically, in the oxide semiconductor, the hydrogen concentration obtained by SIMS is 1×10 20atoms / cm 3 less than, preferably 1×10 19 atoms / cm 3 less than, more preferably 5×10 18 atoms / cm 3 less than, even more preferably 1×10 18 atoms / cm 3 to make it less than.

[0482] By using an oxide semiconductor with sufficiently reduced impurities in the channel formation region of a transistor, stable electrical characteristics can be imparted.

[0483] This embodiment can be implemented in appropriate combination with at least some of the other embodiments described herein.

[0484] (Embodiment 4) In this embodiment, an electronic device including a display device which is one aspect of the present invention will be described.

[0485] FIG. 25A is a view showing the appearance of a camera 8000 with a finder 8100 attached. An imaging device is provided in the camera 8000. The camera 8000 can be, for example, a digital camera. In FIG. 25A, the camera 8000 and the finder 8100 are regarded as separate electronic devices and are configured to be detachable from each other, but a finder including a display device may be built in the housing 8001 of the camera 8000.

[0486] The camera 8000 includes a housing 8001, a display unit 8002, operation buttons 8003, a shutter button 8004, and the like. A detachable lens 8006 is attached to the camera 8000.

[0487] Here, the camera 8000 is configured such that the lens 8006 can be removed from the housing 8001 and replaced, but the lens 8006 and the housing may be integrated.

[0488] The camera 8000 can capture images by pressing the shutter button 8004. Also, the display unit 8002 has a function as a touch panel, and it is also possible to capture images by touching the display unit 8002.

[0489] The housing 8001 of the camera 8000 has a mount with electrodes, and in addition to the viewfinder 8100, a strobe device or the like can be connected.

[0490] The viewfinder 8100 has a housing 8101, a display unit 8102, buttons 8103, etc. The viewfinder 8100 can be an electronic viewfinder.

[0491] The housing 8101 has a mount that engages with the mount of the camera 8000, and the viewfinder 8100 can be attached to the camera 8000. Also, the mount has electrodes, and images received from the camera 8000 via the electrodes can be displayed on the display unit 8102.

[0492] The button 8103 has a function as a power button. By operating the button 8103, the display on the display unit 8102 can be switched on and off.

[0493] The display device according to one aspect of the present invention can be applied to the display unit 8002 of the camera 8000 and the display unit 8102 of the viewfinder 8100. Since the display device according to one aspect of the present invention has extremely high definition, even when the distance between the display unit 8002 or the display unit 8102 and the user is close, the user cannot visually recognize the pixels, and a more immersive image can be displayed on the display unit 8002 or the display unit 8102. In particular, since the image displayed on the display unit 8102 provided in the viewfinder 8100 is visually recognized by bringing the user's eye close to the eyepiece of the viewfinder 8100, the distance between the user and the display unit 8102 becomes very close. Therefore, it is particularly preferable to apply the display device according to one aspect of the present invention to the display unit 8102. When applying the display device according to one aspect of the present invention to the display unit 8102, the resolution of the image that can be displayed on the display unit 8102 can be 4K, 5K, or higher.

[0494] In addition, it is preferable that the resolution of the image that can be captured by the imaging device provided in the camera 8000 is equal to or higher than the resolution of the image that can be displayed on the display unit 8002 or the display unit 8102. For example, when an image with a resolution of 4K can be displayed on the display unit 8102, it is preferable to provide the camera 8000 with an imaging device that can capture an image with a resolution of 4K or higher. Also, for example, when an image with a resolution of 5K can be displayed on the display unit 8102, it is preferable to provide the camera 8000 with an imaging device that can capture an image with a resolution of 5K or higher.

[0495] FIG. 25B is a diagram showing the appearance of the head-mounted display 8200.

[0496] The head-mounted display 8200 has a mounting portion 8201, a lens 8202, a main body 8203, a display unit 8204, a cable 8205, etc. A battery 8206 is built in the mounting portion 8201.

[0497] The cable 8205 supplies power from the battery 8206 to the main body 8203. The main body 8203 is equipped with a wireless receiver or the like, and can display an image corresponding to the received image data or the like on the display unit 8204. In addition, by capturing the movement of the user's eyeballs and eyelids with a camera provided in the main body 8203 and calculating the coordinates of the user's line of sight based on the information, the user's line of sight can be used as an input means.

[0498] A plurality of electrodes may be provided at positions where the wearing part 8201 touches the user. The main body 8203 may have a function of recognizing the user's line of sight by detecting the current flowing through the electrodes as the user's eyeballs move. In addition, by detecting the current flowing through the electrodes, it may have a function of monitoring the user's pulse. Further, the wearing part 8201 may have various sensors such as a temperature sensor, a pressure sensor, and an acceleration sensor, and may have a function of displaying the user's biological information on the display unit 8204. Also, the movement of the user's head or the like may be detected, and the image displayed on the display unit 8204 may be changed according to the movement.

[0499] The display device according to an aspect of the present invention can be applied to the display unit 8204. Thereby, the head-mounted display 8200 can be made to have a narrow bezel, and a high-quality image can be displayed on the display unit 8204, and an image with a high sense of presence can be displayed.

[0500] FIGS. 25C, 25D, and 25E are views showing the appearance of the head-mounted display 8300. The head-mounted display 8300 includes a housing 8301, a display unit 8302, a band-shaped fixture 8304, and a pair of lenses 8305.

[0501] The user can visually recognize the display on the display unit 8302 through the lens 8305. It is preferable to arrange the display unit 8302 in a curved shape. By arranging the display unit 8302 in a curved shape, the user can feel a high sense of immersion. In the present embodiment, a configuration in which one display unit 8302 is provided is exemplified, but the present invention is not limited thereto. For example, a configuration in which two display units 8302 are provided may be adopted. In this case, if one display unit is arranged in front of one eye of the user, it is possible to perform three-dimensional display using parallax and the like.

[0502] In addition, the display device according to an aspect of the present invention can be applied to the display unit 8302. Since the display device according to an aspect of the present invention has extremely high definition, even when enlarged using the lens 8305 as shown in FIG. 25E, an image with a higher sense of immersion can be displayed without the user visually recognizing the pixels.

[0503] Next, an example of an electronic device different from the electronic devices shown in FIGS. 25A to 25E is shown in FIGS. 26A to 26G.

[0504] The electronic devices shown in FIGS. 26A to 26G include a housing 9000, a display unit 9001, a speaker 9003, operation keys 9005 (including a power switch or an operation switch), connection terminals 9006, a sensor 9007 (having a function of measuring force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, inclination, vibration, odor, or infrared rays), a microphone 9008, and the like.

[0505] The electronic devices shown in FIGS. 26A to 26G have various functions. For example, functions such as displaying various types of information (still images, moving images, text images, etc.) on a display unit, a touch panel function, a function of displaying a calendar, date, or time, etc., a function of controlling processing by various software (programs), a wireless communication function, a function of connecting to various computer networks using the wireless communication function, a function of transmitting or receiving various data using the wireless communication function, a function of reading a program or data recorded on a recording medium and displaying it on the display unit, etc. can be provided. Note that the functions that the electronic devices shown in FIGS. 26A to 26G can have are not limited to these, and they can have various functions. Also, although not shown in FIGS. 26A to 26G, the electronic device may be configured to have a plurality of display units. Further, a camera or the like may be provided in the electronic device, and it may have functions such as a function of taking a still image, a function of taking a moving image, a function of storing the taken image in a recording medium (external or built-in to the camera), a function of displaying the taken image on the display unit, etc.

[0506] Details of the electronic devices shown in FIGS. 26A to 26G will be described below.

[0507] FIG. 26A is a perspective view showing a television device 9100. The television device 9100 can incorporate a display unit 9001 with a large screen, for example, 50 inches or more, or 100 inches or more.

[0508] The display device according to one aspect of the present invention can be applied to the display unit 9001 of the television device 9100. Thereby, the television device 9100 can be made to have a narrow bezel, and high-quality images can be displayed on the display unit 9001, and images with a high sense of presence can be displayed.

[0509] FIG. 26B is a perspective view showing a portable information terminal 9101. The portable information terminal 9101 has one or more functions selected from, for example, a telephone, a notebook, or an information browsing device, etc. Specifically, it can be used as a smartphone. Note that the portable information terminal 9101 may be provided with a speaker 9003, a connection terminal 9006, a sensor 9007, etc. Also, the portable information terminal 9101 can display characters and images on its multiple surfaces. For example, three operation buttons 9050 (also referred to as operation icons or simply icons) can be displayed on one surface of the display unit 9001. Also, information 9051 indicated by a dashed rectangle can be displayed on another surface of the display unit 9001. Note that, as an example of the information 9051, there are displays for notifying incoming calls such as e-mails, SNS (Social Networking Service), or telephone calls, titles of e-mails, SNS, etc., sender names of e-mails, SNS, etc., date and time, time, remaining battery level, antenna reception strength, etc. Or, instead of the information 9051, operation buttons 9050, etc. may be displayed at the position where the information 9051 is displayed.

[0510] The display device according to one aspect of the present invention can be applied to the display unit 9001 included in the portable information terminal 9101. Thereby, the portable information terminal 9101 can be miniaturized, and high-quality images can be displayed on the display unit 9001, and images with a high sense of presence can be displayed.

[0511] FIG. 26C is a perspective view showing a portable information terminal 9102. The portable information terminal 9102 has a function of displaying information on three or more surfaces of the display unit 9001. Here, an example is shown in which information 9052, information 9053, and information 9054 are displayed on different surfaces, respectively. For example, the user of the portable information terminal 9102 can confirm the display (here, information 9053) in a state where the portable information terminal 9102 is stored in the breast pocket of a jacket. Specifically, the telephone number or name, etc. of the caller of an incoming call is displayed at a position where it can be observed from above the portable information terminal 9102. The user can confirm the display and determine whether to answer the call without taking the portable information terminal 9102 out of the pocket.

[0512] The display device according to an aspect of the present invention can be applied to the display unit 9001 of the mobile information terminal 9102. As a result, the mobile information terminal 9101 can be miniaturized, and high-quality images can be displayed on the display unit 9001, and images with a high sense of presence can be displayed.

[0513] FIG. 26D is a perspective view showing a wristwatch-type mobile information terminal 9200. The mobile information terminal 9200 can execute various applications such as mobile phones, e-mails, text browsing and creation, music playback, Internet communication, and computer games. In addition, the display surface of the display unit 9001 is provided in a curved shape, and display can be performed along the curved display surface. Further, the mobile information terminal 9200 can execute short-range wireless communication conforming to a communication standard. For example, it can also make hands-free calls by communicating with a wirelessly communicable headset. In addition, the mobile information terminal 9200 has a connection terminal 9006 and can directly exchange data with other information terminals via a connector. Charging can also be performed via the connection terminal 9006. Note that the charging operation may be performed by wireless power supply without using the connection terminal 9006.

[0514] The display device according to an aspect of the present invention can be applied to the display unit 9001 of the mobile information terminal 9200. As a result, the mobile information terminal 9200 can be made to have a narrow bezel, and high-quality images can be displayed on the display unit 9001, and images with a high sense of presence can be displayed.

[0515] Figs. 26E, 26F and 26G are perspective views showing a foldable mobile information terminal 9201. Further, Fig. 26E is a perspective view of the mobile information terminal 9201 in an unfolded state, Fig. 26F is a perspective view of the mobile information terminal 9201 in a state midway through changing from one of the unfolded state or the folded state to the other, and Fig. 26G is a perspective view of the mobile information terminal 9201 in a folded state. The mobile information terminal 9201 is excellent in portability in the folded state and excellent in the listability of display due to a seamless wide display area in the unfolded state. The display unit 9001 included in the mobile information terminal 9201 is supported by three housings 9000 connected by a hinge 9055. By bending between the two housings 9000 via the hinge 9055, the mobile information terminal 9201 can be reversibly deformed from the unfolded state to the folded state. For example, the mobile information terminal 9201 can be bent with a radius of curvature of 1 mm or more and 150 mm or less.

[0516] The display device according to one aspect of the present invention can be applied to the display unit 9001 included in the mobile information terminal 9201. Thereby, the mobile information terminal 9201 can be made to have a narrow bezel, and a high-quality image can be displayed on the display unit 9001, and an image with a high sense of presence can be displayed.

[0517] The configuration examples illustrated in the present embodiment, and the corresponding drawings and the like can be implemented by appropriately combining at least a part thereof with other configuration examples, drawings, and the like.

[0518] The present embodiment can be implemented by appropriately combining at least a part thereof with other embodiments described in this specification.

Example

[0519] In this example, using circuit simulation, in the configuration of the pixel circuit shown in Fig. 1, the boosting operation was confirmed with the timing chart shown in Fig. 2.

[0520] In the simulation, transistor 101 and transistor 102 were each an OS transistor with a channel length of 200 μm and a channel width of 60 μm. Transistor 103 and transistor 104 were each an OS transistor with a channel length of 60 μm and a channel width of 60 μm. The capacitance values of capacitor element 111 and capacitor element 112 were each set to 7.26 fF. As the voltages applied to wiring 121 and wiring 122, High was 5 V and Low was 0 V. Wiring 131 was simulated at 0.5 V, 1.0 V, 1.5 V, 2.0 V, 2.5 V, 3.0 V, 3.5 V, and 4.0 V for “Vdata” respectively. SmartSpice from SILVACO was used as the circuit simulation software. Wiring 127 was set to “Vref” at 0.5 V, wiring 128 was set to “Vano” at 8.0 V, and wiring 129 was set to “Vcath” at -1.5 V.

[0521] The simulation results are shown in FIG. 27. In FIG. 27, the horizontal axis indicates the time (Time) according to the timing chart, and the vertical axis indicates the minimum value of the potential V of node ND1 after time T4. ND1 Also, the ideal value and the simulation result of the potential V of node ND1 are shown in Table 1. ND1

[0522] Note that the ideal value of the potential V shown in Table 1 indicates the value obtained by setting the constant a, the constant b, and the constant c to zero in the aforementioned formula (9). ND1

[0523]

Table 1

[0524] As shown in FIG. 27 and Table 1, the potential V of node ND1 obtained by the simulation ND1It was confirmed that it was equivalent to the ideal value. The difference from the ideal value is considered to be the influence of feed-through, charge injection, etc. when the transistors 102, 103, and 104, which are indicated by the constant a, the constant b, and the constant c, are each in a non-conductive state. It was found that the display device according to one aspect of the present invention can boost the voltage to a voltage higher than the voltage corresponding to the image data supplied to the pixel 10 and supply the voltage to the transistor 101 that functions as a driving transistor. Therefore, it was found that the current flowing through the light-emitting device 114 can be increased.

Example

[0525] In this example, the results of simulations performed under conditions different from those of Example 1 are shown. For the circuit configuration, refer to FIG. 1, and for the timing chart, refer to FIG. 2.

[0526] In the simulation, the transistor 101 and the transistor 102 were each an OS transistor with a channel length of 200 μm and a channel width of 60 μm. The transistor 103 and the transistor 104 were each an OS transistor with a channel length of 60 μm and a channel width of 60 μm. The capacitance values of the capacitor elements 111 and 112 were each set to 7.26 fF. As the voltages applied to the wirings 121 and 122, High was set to 5 V and Low was set to 0 V. The simulation was performed with the wiring 131 having “Vdata” at 4.3 V, the wiring 127 having “Vref” at 1.1 V, the wiring 128 having “Vano” at 8.0 V, and the wiring 129 having “Vcath” at -1.5 V. SPICE was used as the circuit simulation software.

[0527] The simulation results are shown in FIG. 28. In FIG. 28, the horizontal axis represents the time (Time) according to the timing chart, and the vertical axis represents the potentials V of the wirings 121, 122, 131, the node ND1, and the node ND2, respectively.

[0528] As shown in FIG. 28, it was confirmed that the potential V of the node ND1 obtained by simulation became 6.1 V, which was higher than the given potential (the potential of the wiring 131).

Explanation of Signs

[0529] 10: Pixel, 10A: Pixel, 10B: Sub-pixel, 10G: Sub-pixel, 10R: Sub-pixel, 20: First layer, 30: Second layer, 51a: Display area, 51b: Display area, 51c: Display area, 53: Pixel electrode, 53a: Pixel electrode, 53b: Pixel electrode, 53c: Pixel electrode, 100: Display device, 101: Transistor, 102: Transistor, 103: Transistor, 104: Transistor, 105: Transistor, 111: Capacitor element, 112: Capacitor element, 114: Light-emitting device, 121: Wiring, 122: Wiring, 127: Wiring, 128: Wiring, 129: Wiring, 130: Driving circuit section, 131: Wiring, 140a: Driving circuit section, 140b: Driving circuit section, 141: Wiring, 143: Wiring, 150: Pixel section, 200A: Transistor, 200B: Transistor, 200C: Transistor, 205: Conductor, 214: Insulator, 216: Insulator, 222: Insulator, 224: Insulator, 230a: Metal oxide, 230b: Metal oxide, 230c: Metal oxide, 230: Metal oxide, 240a: Conductor, 240b: Conductor, 240: Conductor, 241a: Insulator, 241b: Insulator, 241: Insulator, 242a: Conductor, 242b: Conductor, 242: Conductor, 243a: Region, 243b: Region, 244: Insulator, 250: Insulator, 252: Metal oxide, 254: Insulator, 260a: Conductor, 260b: Conductor, 260: Conductor, 270: Insulator, 271: Insulator, 272: Insulator, 274: Insulator, 280: Insulator, 281: Insulator, 301a: Conductor, 301b: Conductor, 305: Conductor, 311: Conductor, 313: Conductor, 317: Conductor, 321: Lower electrode, 323: Insulator, 325: Upper electrode, 331: Conductor, 333: Conductor, 335: Conductor, 337: Conductor, 341: Conductor, 343: Conductor, 347: Conductor, 351: Conductor, 353: Conductor, 355: Conductor, 357: Conductor, 361: Insulator, 363: Insulator, 403: Element isolation layer, 405: Insulator, 407: Insulator, 409: Insulator, 411: Insulator, 413: Insulator, 415: Insulator, 417: Insulator, 419: Insulator, 421: Insulator, 441: Transistor, 443: Conductor, 445: Insulator, 447: Semiconductor region, 449a: Low-resistance region, 449b: Low-resistance region, 451: Conductor, 453: Conductor, 455: Conductor, 457: Conductor, 459: Conductor, 461: Conductor,463: Conductor, 465: Conductor, 467: Conductor, 469: Conductor, 471: Conductor, 501: Insulator, 503: Insulator, 505: Insulator, 507: Insulator, 509: Insulator, 572: Light-emitting device, 601: Transistor, 602: Transistor, 603: Transistor, 613: Insulator, 614: Insulator, 616: Insulator, 622: Insulator, 624: Insulator, 644: Insulator, 654: Insulator, 674: Insulator, 680: Insulator, 681: Insulator, 701: Substrate, 705: Substrate, 712: Sealing material, 716: FPC, 721: Hole injection layer, 722: Hole transport layer, 723: Light-emitting layer, 724: Electron transport layer, 725: Electron injection layer, 730: Insulator, 732: Encapsulation layer, 734: Insulator, 736: Coloring layer, 738: Light-shielding layer, 750: Transistor, 760: Connection electrode, 772: Conductor, 778: Structure, 780: Anisotropic conductor, 782: Light-emitting device, 786a: EL layer, 786b: EL layer, 786c: EL layer, 786: EL layer, 788: Conductor, 790: Capacitor element, 792: Charge generation layer, 800: Transistor, 801a: Conductor, 801b: Conductor, 805: Conductor, 811: Conductor, 813: Conductor, 814: Insulator, 816: Insulator, 817: Conductor, 821: Insulator, 822: Insulator, 824: Insulator, 844: Insulator, 853: Conductor, 854: Insulator, 855: Conductor, 874: Insulator, 880: Insulator, 881: Insulator, 8000: Camera, 8001: Housing, 8002: Display unit, 8003: Operation button, 8004: Shutter button, 8006: Lens, 8100: Finder, 8101: Housing, 8102: Display unit, 8103: Button, 8200: Head-mounted display, 8201: Mounting part, 8202: Lens, 8203: Main body, 8204: Display unit, 8205: Cable, 8206: Battery, 8300: Head-mounted display, 8301: Housing, 8302: Display unit, 8304: Fixture, 8305: Lens, 9000: Housing, 9001: Display unit, 9003: Speaker, 9005: Operation key, 9006: Connection terminal, 9007: Sensor, 9008: Microphone, 9050: Operation button, 9051: Information, 9052: Information, 9053: Information, 9054: Information, 9055: Hinge, 9100: Television device, 9101: Portable information terminal, 9102: Portable information terminal, 9200: Portable information terminal,9201: Mobile information terminal,

Claims

[Claim 1] a first wiring, a second wiring, a third wiring, a fourth wiring, a light emitting device, a first transistor, a second transistor, a third transistor, a fourth transistor, a first capacitance element, and a second capacitance element; one electrode of the light emitting device is electrically connected to one of the source and drain of the first transistor; a gate of the first transistor is electrically connected to one electrode of the first capacitance element and one of a source and a drain of the second transistor; the other of the source and the drain of the first transistor is electrically connected to one electrode of the second capacitance element; one electrode of the second capacitor is electrically connected to the first wiring having a function of supplying a first potential; the other electrode of the second capacitance element is electrically connected to the other electrode of the first capacitance element, one of the source or the drain of the third transistor, and one of the source or the drain of the fourth transistor; a gate of the second transistor is electrically connected to the second wiring; a gate of the fourth transistor is electrically connected to the second wiring; a gate of the third transistor is electrically connected to the third wiring; the other of the source and the drain of the second transistor is electrically connected to the fourth wiring; the other of the source and the drain of the third transistor is electrically connected to the fourth wiring; the other of the source and the drain of the fourth transistor is electrically connected to a fifth wiring; A display device, wherein the first wiring, the second wiring, and the third wiring extend in a first direction when viewed from above.

Images