Semiconductor device

Abstract

Provided is a semiconductor having a small occupied area. This semiconductor device has a first conductive layer, a second conductive layer on the first conductive layer, a first insulating layer on the second conductive layer, a semiconductor layer and a third conductive layer on the first insulating layer, a second insulating layer on the semiconductor layer and the third conductive layer, and a fourth conductive layer on the second insulating layer. At least a portion of the second conductive layer is in contact with the upper surface of the first conductive layer; the semiconductor layer is in contact with the upper surface of the first conductive layer, the side surface of the second conductive layer, the third conductive layer, and the side surface of the first insulating layer; and the fourth conductive layer overlaps the semiconductor layer with the second insulating layer interposed therebetween.

Description

Semiconductor Devices

[0001] BACKGROUND OF THE INVENTION 1. Field of the Invention One embodiment of the present invention relates to a semiconductor device and a manufacturing method thereof. 2. Description of the Related Art One embodiment of the present invention relates to a transistor and a manufacturing method thereof.

[0002] One embodiment of the present invention is not limited to the above technical field, and examples of the technical field of one embodiment of the present invention include semiconductor devices, display devices, light-emitting devices, power storage devices, memory devices, electronic devices, lighting devices, input devices (e.g., touch sensors), input / output devices (e.g., touch panels), driving methods thereof, and manufacturing methods thereof.

[0003] In this specification and the like, a semiconductor device is a device that utilizes semiconductor characteristics, and refers to a circuit including a semiconductor element (transistor, diode, photodiode, etc.), a device having such a circuit, etc. Also, it refers to any device that can function by utilizing semiconductor characteristics. For example, an integrated circuit, a chip including an integrated circuit, and an electronic component in which a chip is housed in a package are examples of semiconductor devices. Furthermore, a memory device, a display device, a light-emitting device, a lighting device, and an electronic device may themselves be semiconductor devices and each may have a semiconductor device.

[0004] Semiconductor devices including transistors are widely used in electronic devices. For example, in display devices, pixel size can be reduced by reducing the area occupied by a transistor, and higher definition can be achieved. Therefore, miniaturization of transistors is desired.

[0005] As devices requiring high-definition display devices, devices for virtual reality (VR), augmented reality (AR), substitutional reality (SR), and mixed reality (MR) are being actively developed.

[0006] As display devices, for example, light-emitting devices having organic EL (Electro Luminescence) elements or light-emitting diodes (LEDs) have been developed.

[0007] Patent Document 1 discloses a high-definition display device using organic EL elements.

[0008] International Publication No. 2016 / 038508

[0009] An object of one embodiment of the present invention is to provide a transistor with a small size. Another object is to provide a transistor with a short channel length. Another object is to provide a transistor with high on-state current. Another object is to provide a transistor with favorable electrical characteristics. Another object is to provide a semiconductor device with a small occupation area. Another object is to provide a semiconductor device with low wiring resistance. Another object is to provide a semiconductor device or display device with low power consumption. Another object is to provide a highly reliable transistor, semiconductor device, or display device. Another object is to provide a display device that can easily be made high-definition. Another object is to provide a method for manufacturing a semiconductor device or display device with high productivity. Another object is to provide a novel transistor, semiconductor device, or display device, and a manufacturing method thereof.

[0010] Note that the description of these problems does not preclude the existence of other problems. One embodiment of the present invention does not necessarily have to solve all of these problems. Problems other than these can be extracted from the description in the specification, drawings, and claims.

[0011] One embodiment of the present invention is a semiconductor device including a semiconductor layer, a first conductive layer, a second conductive layer, a third conductive layer, a fourth conductive layer, a first insulating layer, and a second insulating layer, in which at least a part of the second conductive layer is in contact with a top surface of the first conductive layer, the first insulating layer is located on the second conductive layer, the third conductive layer is located on the first insulating layer, the semiconductor layer is in contact with a top surface of the first conductive layer, a side surface of the second conductive layer, and a side surface of the third conductive layer and the first insulating layer, the second insulating layer is located on the semiconductor layer, and the fourth conductive layer is located on the second insulating layer and overlaps with the semiconductor layer with the second insulating layer interposed therebetween.

[0012] Alternatively, one embodiment of the present invention includes a semiconductor layer, a first conductive layer, a second conductive layer, a third conductive layer, a fourth conductive layer, a first insulating layer, and a second insulating layer, in which the second conductive layer is in contact with a top surface of the first conductive layer and has a first opening reaching the first conductive layer, the first insulating layer is located over the second conductive layer and has a second opening overlapping with the first opening, and the third conductive layer is located over the first insulating layer and has a first opening and a third opening overlapping the second opening, the semiconductor layer being in contact with the top surface of the first conductive layer via the first to third openings, and also in contact with a side surface of the second conductive layer in the first opening, the third conductive layer, and a side surface of the first insulating layer in the second opening, the second insulating layer being located on the semiconductor layer, and the fourth conductive layer being located on the second insulating layer and overlapping with the semiconductor layer via the second insulating layer.

[0013] The shortest distance from the upper surface of the first conductive layer to the upper surface of the second conductive layer is preferably longer than the shortest distance from the upper surface of the first conductive layer to the lower surface of the fourth conductive layer.

[0014] The conductivity of the second conductive layer is preferably higher than the conductivity of the first conductive layer.

[0015] The semiconductor layer preferably contacts the top and side surfaces of the third conductive layer.

[0016] The semiconductor layer preferably comprises a metal oxide.

[0017] Furthermore, a metal oxide containing the metal contained in the second conductive layer may be provided between the semiconductor layer and the second conductive layer.

[0018] Alternatively, one embodiment of the present invention is a semiconductor device including a first metal oxide layer, a second metal oxide layer, a first conductive layer, a second conductive layer, a third conductive layer, a fourth conductive layer, a first insulating layer, and a second insulating layer, wherein at least a part of the second conductive layer is in contact with a top surface of the first conductive layer, the first insulating layer is located on the second conductive layer, the third conductive layer is located on the first insulating layer, the first metal oxide layer is in contact with a top surface of the first conductive layer, a side surface of the second metal oxide layer, and a side surface of the third conductive layer and the first insulating layer, the second metal oxide layer is in contact with a side surface of the second conductive layer, the second insulating layer is located on the first metal oxide layer, and the fourth conductive layer is located on the second insulating layer and overlaps with the first metal oxide layer with the second insulating layer interposed therebetween, and the second metal oxide layer and the second conductive layer contain the same metal element.

[0019] According to one embodiment of the present invention, a transistor with a small size can be provided. Alternatively, a transistor with a short channel length can be provided. Alternatively, a transistor with high on-state current can be provided. Alternatively, a transistor with favorable electrical characteristics can be provided. Alternatively, a semiconductor device with a small occupation area can be provided. Alternatively, a semiconductor device with low wiring resistance can be provided. Alternatively, a semiconductor device or display device with low power consumption can be provided. Alternatively, a highly reliable transistor, semiconductor device, or display device can be provided. Alternatively, a display device that can easily be made high-definition can be provided. Alternatively, a method for manufacturing a semiconductor device or display device with high productivity can be provided. Alternatively, a novel transistor, semiconductor device, or display device, and a manufacturing method thereof can be provided.

[0020] Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all of these effects. Effects other than these can be extracted from the description in the specification, drawings, and claims.

[0021] FIG. 1A is a top view showing an example of a semiconductor device. FIGS. 1B and 1C are cross-sectional views showing an example of a semiconductor device. FIG. 2A is a top view showing an example of a semiconductor device. FIG. 2B is a cross-sectional view showing an example of a semiconductor device. FIGS. 3A to 3C are cross-sectional views showing an example of a semiconductor device. FIG. 4A is a top view showing an example of a semiconductor device. FIGS. 4B and 4C are cross-sectional views showing an example of a semiconductor device. FIG. 5A is a top view showing an example of a semiconductor device. FIGS. 5B and 5C are cross-sectional views showing an example of a semiconductor device. FIG. 6A is a top view showing an example of a semiconductor device. FIGS. 6B and 6C are cross-sectional views showing an example of a semiconductor device. FIG. 7A is a top view showing an example of a semiconductor device. FIGS. 7B and 7C are cross-sectional views showing an example of a semiconductor device. FIG. 8A is a top view showing an example of a semiconductor device. FIGS. 8B and 8C are cross-sectional views showing an example of a semiconductor device. FIGS. 9A and 9B are cross-sectional views showing an example of a semiconductor device. FIGS. 10A to 10I are circuit diagrams showing an example of a semiconductor device. FIGS. 11A to 11C are cross-sectional views showing an example of a semiconductor device. FIG. 12A is a top view showing an example of a semiconductor device. FIG. 12B is a cross-sectional view showing an example of a semiconductor device. FIGS. 13A and 13B are cross-sectional views showing an example of a semiconductor device. FIG. 14A is a top view showing an example of a semiconductor device. FIGS. 14B and 14C are cross-sectional views showing an example of a semiconductor device. FIG. 15A is a top view showing an example of a semiconductor device. FIG. 15B is a cross-sectional view showing an example of a semiconductor device. FIG. 16A is a top view showing an example of a semiconductor device. FIG. 16B is a cross-sectional view showing an example of a semiconductor device. FIGS. 17A to 17D are cross-sectional views showing an example of a method for manufacturing a semiconductor device. FIGS. 18A to 18C are cross-sectional views showing an example of a method for manufacturing a semiconductor device. FIGS. 19A to 19C are cross-sectional views showing an example of a method for manufacturing a semiconductor device. FIG. 20 is a perspective view showing an example of a display device. FIGS. 21A and 21B are cross-sectional views showing an example of a display device. FIG. 22 is a cross-sectional view showing an example of a display device. FIGS. 23A to 23C are cross-sectional views showing an example of a display device. FIGS. 24A and 24B are cross-sectional views showing an example of a display device. FIG. 25 is a cross-sectional view showing an example of a display device.FIG. 26 is a cross-sectional view showing an example of a display device. FIG. 27 is a cross-sectional view showing an example of a display device. FIGS. 28A and 28B are cross-sectional views showing an example of a display device. FIGS. 29A to 29F are cross-sectional views showing an example of a manufacturing method of a display device. FIGS. 30A to 30D are views showing an example of an electronic device. FIGS. 31A to 31F are views showing an example of an electronic device. FIGS. 32A to 32G are views showing an example of an electronic device.

[0022] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various changes can be made in form and detail without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0023] In the configuration of the invention described below, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings, and repeated explanations thereof will be omitted. Furthermore, when referring to similar functions, the same hatching pattern may be used and no particular reference numeral may be assigned.

[0024] Furthermore, for ease of understanding, the position, size, range, etc. of each component shown in the drawings may not represent the actual position, size, range, etc. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings.

[0025] In this specification, the ordinal numbers "first" and "second" are used for convenience and do not limit the number of components or the order of the components (for example, the order of processes or the order of stacking). Furthermore, the ordinal numbers assigned to components in one part of this specification may not match the ordinal numbers assigned to the same components in other parts of this specification or in the claims.

[0026] The terms "film" and "layer" can be interchangeable depending on the circumstances. For example, the term "conductive layer" can be changed to the term "conductive film." Or, for example, the term "insulating film" can be changed to the term "insulating layer."

[0027] A transistor is a type of semiconductor element that can amplify current or voltage, and perform a switching operation to control conduction or non-conduction. The term "transistor" as used herein includes an insulated gate field effect transistor (IGFET) and a thin film transistor (TFT).

[0028] Furthermore, the functions of "source" and "drain" may be interchangeable when transistors of different polarities are used, or when the direction of current flow changes during circuit operation, etc. For this reason, the terms "source" and "drain" may be used interchangeably in this specification.

[0029] In this specification, "electrically connected" includes a connection via "something that has some kind of electrical action." Here, "something that has some kind of electrical action" is not particularly limited as long as it allows electrical signals to be transmitted and received between the connected objects. For example, "something that has some kind of electrical action" includes electrodes or wiring, as well as switching elements such as transistors, resistive elements, coils, capacitive elements, and other elements with various functions.

[0030] In this specification and the like, unless otherwise specified, the off-state current refers to the leakage current between the source and drain when the transistor is in an off state (also referred to as a non-conducting state or a cut-off state). Unless otherwise specified, the off-state current refers to the leakage current between the source and the gate when the voltage V ｇｓ is the threshold voltage V ｔｈ (For p-channel transistors, V ｔｈ This refers to a state of being (higher than)

[0031] In this specification, the phrase "top surface shapes are approximately the same" refers to at least a portion of the contours of stacked layers overlapping. For example, this includes cases where the upper and lower layers are processed using the same mask pattern or a portion of the same mask pattern. However, strictly speaking, the contours may not overlap, and the upper layer may be located inside the lower layer, or the upper layer may be located outside the lower layer. In these cases, the phrase "top surface shapes are approximately the same" may also be used. Furthermore, when the top surface shapes are the same or approximately the same, it can also be said that the edges are aligned or approximately aligned.

[0032] In this specification, a tapered shape refers to a shape in which at least a portion of the side surface of a structure is inclined relative to the substrate surface or the surface to be formed. For example, it is preferable to have a region in which the angle (also called the taper angle) between the inclined side surface and the substrate surface or the surface to be formed is greater than 0 degrees and less than 90 degrees. The side surface of the structure, the substrate surface, and the surface to be formed do not necessarily need to be completely flat, and may be approximately planar with a slight curvature or approximately planar with a slight unevenness.

[0033] In this specification and the like, an oxynitride refers to a material having a composition in which oxygen is contained in a larger amount than nitrogen, and a nitride oxide refers to a material having a composition in which nitrogen is contained in a larger amount than oxygen.

[0034] For example, secondary ion mass spectrometry (SIMS) or X-ray photoelectron spectroscopy (XPS) can be used to analyze the content of elements such as hydrogen, oxygen, and nitrogen. XPS is suitable when the content of the target element is high (e.g., 0.5 atomic % or more, or 1 atomic % or more). On the other hand, SIMS is suitable when the content of the target element is low (e.g., 0.5 atomic % or less, or 1 atomic % or less). When comparing the content of elements, it is more preferable to perform a combined analysis using both SIMS and XPS analytical techniques.

[0035] In this specification and the like, when it is stated that A is in contact with B, it means that at least a part of A is in contact with B. Therefore, for example, it can be rephrased as saying that A has a region in contact with B.

[0036] In this specification and the like, when it is stated that A is located on B, it means that at least a part of A is located on B. Therefore, for example, it can be rephrased as, A has a region located on B.

[0037] In this specification and the like, when it is stated that A overlaps with B, it means that at least a part of A overlaps with B. Therefore, for example, it can be rephrased as saying that A has an overlapping region with B.

[0038] In this specification, etc., a device fabricated using a metal mask or an FMM (fine metal mask, high-resolution metal mask) may be referred to as a device with an MM (metal mask) structure. Also, in this specification, etc., a device fabricated without using a metal mask or an FMM may be referred to as a device with an MML (metal maskless) structure.

[0039] In this specification and the like, a structure in which different light-emitting layers are formed for light-emitting elements (also referred to as light-emitting devices) with different emission wavelengths is sometimes referred to as an SBS (Side By Side) structure. The SBS structure allows the materials and configuration to be optimized for each light-emitting element, increasing the degree of freedom in selecting materials and configurations and making it easier to improve brightness and reliability.

[0040] In this specification and the like, holes or electrons may be referred to as "carriers." Specifically, a hole injection layer or an electron injection layer may be referred to as a "carrier injection layer," a hole transport layer or an electron transport layer may be referred to as a "carrier transport layer," and a hole block layer or an electron block layer may be referred to as a "carrier block layer." Note that the above-mentioned carrier injection layer, carrier transport layer, and carrier block layer may not be clearly distinguishable. Furthermore, one layer may have two or three functions among the carrier injection layer, carrier transport layer, and carrier block layer.

[0041] In this specification and the like, a light-emitting element has an EL layer between a pair of electrodes. The EL layer has at least a light-emitting layer. Here, examples of layers (also referred to as functional layers) included in the EL layer include a light-emitting layer, a carrier injection layer (a hole injection layer and an electron injection layer), a carrier transport layer (a hole transport layer and an electron transport layer), and a carrier block layer (a hole block layer and an electron block layer). In this specification and the like, a light-receiving element (also referred to as a light-receiving device) has at least an active layer that functions as a photoelectric conversion layer between a pair of electrodes. In this specification and the like, one of the pair of electrodes may be referred to as a pixel electrode, and the other as a common electrode.

[0042] In this specification and the like, the sacrificial layer (which may also be referred to as a mask layer) is located above at least the light-emitting layer (more specifically, a layer that is processed into an island shape among the layers that make up the EL layer), and has the function of protecting the light-emitting layer during the manufacturing process.

[0043] In this specification and the like, the term "step discontinuity" refers to a phenomenon in which a layer, film, or electrode is separated due to the shape of the surface on which it is formed (for example, a step or the like).

[0044] Embodiment 1 In this embodiment, a semiconductor device of one embodiment of the present invention will be described with reference to FIGS.

[0045] One embodiment of the present invention includes a semiconductor layer, a first conductive layer, a second conductive layer, a third conductive layer, a fourth conductive layer, a first insulating layer, and a second insulating layer.

[0046] The first conductive layer functions as one of a source electrode and a drain electrode of the transistor.

[0047] The second conductive layer is located on the first conductive layer. At least a portion of the second conductive layer is in contact with the upper surface of the first conductive layer. The conductivity of the second conductive layer is preferably higher than that of the first conductive layer. The second conductive layer preferably functions as an auxiliary wiring for the first conductive layer. The second conductive layer may have a first opening (which may also be referred to as a first opening) that reaches the first conductive layer. Note that in this specification and the like, the term "opening" can be replaced with "opening."

[0048] The first insulating layer is located on the second conductive layer and may have a second opening overlapping the first opening.

[0049] The third conductive layer is located on the first insulating layer. The third conductive layer functions as the other of the source electrode and the drain electrode of the transistor. For example, the third conductive layer has a third opening overlapping the first opening and the second opening.

[0050] The semiconductor layer is in contact with the top surface of the first conductive layer, the side surface of the first insulating layer, and the third conductive layer. The semiconductor layer is preferably in contact with the side surface of the second conductive layer. The semiconductor layer may be in contact with an oxide containing the same metal as the metal contained in the second conductive layer. The oxide may be formed between the semiconductor layer and the second conductive layer. When the first to third openings are provided, the semiconductor layer is in contact with the top surface of the first conductive layer through the first to third openings, and is in contact with the side surface of the second conductive layer in the first opening, the third conductive layer, and the side surface of the first insulating layer in the second opening. The semiconductor layer preferably contains a metal oxide.

[0051] The second insulating layer is located on the semiconductor layer and functions as a gate insulating layer.

[0052] The fourth conductive layer is located on the second insulating layer and overlaps with the semiconductor layer with the second insulating layer interposed therebetween. The fourth conductive layer functions as a gate electrode of the transistor. When the first to third openings described above are provided, the fourth conductive layer overlaps with the semiconductor layer with the second insulating layer interposed therebetween at positions overlapping with the first, second, and third openings.

[0053] The first insulating layer has a portion in contact with a channel formation region in the semiconductor layer. The channel formation region is a high-resistance region with a low carrier concentration. The channel formation region can be said to be i-type (intrinsic) or substantially i-type. If the first insulating layer has a layer with a high oxygen content, it becomes easy to form an i-type region in the region in contact with the first insulating layer in the semiconductor layer and in its vicinity.

[0054] The second conductive layer contacts a region of the semiconductor layer where the gate electric field is not easily applied (also referred to as an offset region). If the resistance of the offset region is high, the field-effect mobility of the transistor may decrease. By providing the second conductive layer in contact with the semiconductor layer, the resistance of the region of the semiconductor layer that contacts the second conductive layer and its vicinity can be reduced. This makes it possible to suppress a decrease in field-effect mobility due to the offset region.

[0055] Specifically, when the second conductive layer and the semiconductor layer are in contact with each other, the second conductive layer extracts oxygen contained in the semiconductor layer during heat treatment or the like, which easily forms oxygen vacancies in the semiconductor layer. Impurities such as hydrogen then enter the oxygen vacancies, causing the impurities to function as donors and increasing the carrier concentration. Therefore, the resistance of the region of the semiconductor layer in contact with the second conductive layer and its vicinity can be reduced.

[0056] It should be noted that grooves (slits) may be provided in place of the first opening, the second opening, and the third opening, respectively.

[0057] [Transistor 100] FIGS. 1A and 2A show top views of the transistor 100. FIG. 2A differs from FIG. 1A in that it shows the diameter D143 and the channel width W100 but does not show the dashed-dotted line B1-B2. Insulating layers are not shown in FIGS. 1A and 2A. Note that some components are also not shown in the other top views.

[0058] 1B and 2B are cross-sectional views taken along dashed lines A1-A2 in FIGS. 1A and 2A. FIG. 2B can also be considered an enlarged view of FIG. 1B. FIG. 1B shows openings 141, 143, and 148 and shortest distances T1 and T2, while FIG. 2B shows diameter D143, channel width W100, channel length L100, region 108n, thickness T110, and angle θ110. Other elements are shown in common in FIGS. 1B and 2B. FIG. 1C is a cross-sectional view taken along dashed lines B1-B2 in FIG. 1A.

[0059] The transistor 100 is provided over a substrate 102. The transistor 100 includes a conductive layer 112a, a conductive layer 103, an insulating layer 110 (insulating layers 110a, 110b, and 110c), a semiconductor layer 108, a conductive layer 112b, an insulating layer 106, and a conductive layer 104. Each layer included in the transistor 100 may have a single-layer structure or a stacked-layer structure. Note that the conductive layer 103 and the insulating layer 110 do not necessarily have to be included as components of the transistor 100. In other words, it can be said that a semiconductor device of one embodiment of the present invention includes the transistor 100, the conductive layer 103, and the insulating layer 110.

[0060] The conductive layer 112a is provided over the substrate 102. The conductive layer 112a functions as one of a source electrode and a drain electrode of the transistor 100.

[0061] 1C shows an example in which the side surfaces of the conductive layer 112a are not covered with the conductive layer 103, but the present invention is not limited to this. Part or all of the side surfaces of the conductive layer 112a may be covered with the conductive layer 103. For example, part of the conductive layer 112a may be in contact with the substrate 102.

[0062] The conductive layer 103 is located over the conductive layer 112a. At least a portion of the conductive layer 103 is in contact with the top surface of the conductive layer 112a. The conductive layer 103 can function as an auxiliary wiring for the conductive layer 112a. The conductive layer 103 can also function as a wiring. An opening 148 reaching the conductive layer 112a is provided in the conductive layer 103.

[0063] The insulating layer 110 is located on the substrate 102, the conductive layer 112a, and the conductive layer 103. The insulating layer 110 has an opening 141 that overlaps with the opening 148.

[0064] The insulating layer 110 has a laminated structure of an insulating layer 110a, an insulating layer 110b on the insulating layer 110a, and an insulating layer 110c on the insulating layer 110b.

[0065] The conductive layer 112b is located over the insulating layer 110. The conductive layer 112b has an opening 143 that overlaps with the openings 141 and 148. The conductive layer 112b functions as the other of the source and drain electrodes of the transistor.

[0066] The semiconductor layer 108 is in contact with the top surface of the conductive layer 112a, the side surface of the insulating layer 110, and the top surface and side surface of the conductive layer 112b. The semiconductor layer 108 is provided in contact with an end portion of the insulating layer 110 on the opening 141 side (which can also be referred to as a sidewall of the opening 141) and an end portion of the conductive layer 112b on the opening 143 side (which can also be referred to as a sidewall of the opening 143). The semiconductor layer 108 is preferably in contact with the side surface of the conductive layer 103. The semiconductor layer 108 is preferably provided in contact with an end portion of the conductive layer 103 on the opening 148 side (which can also be referred to as a sidewall of the opening 148). The semiconductor layer 108 is in contact with the conductive layer 112a through the openings 141, 143, and 148.

[0067] 3A , a metal oxide 103s may be formed between the conductive layer 103 and the semiconductor layer 108. For example, the metal oxide 103s is formed when a metal contained in the conductive layer 103 is oxidized by oxygen contained in the semiconductor layer 108. That is, it can be said that the metal oxide 103s contains the same metal as the metal contained in the conductive layer 103. Since the conductive layer 103 and the semiconductor layer 108 do not need to be electrically connected to each other, the metal oxide 103s may be formed on part or the entire sidewall of the opening 148. Furthermore, the conductive layer 103 and the semiconductor layer 108 do not need to be in contact with each other. The presence of the metal oxide 103s can be confirmed by, for example, energy dispersive X-ray spectrometry (EDX).

[0068] In the semiconductor layer 108, a region in contact with the conductive layer 112a functions as one of a source region and a drain region, and a region in contact with the conductive layer 112b functions as the other of the source region and the drain region. ＋ Type area, or n ＋The region in contact with the insulating layer 110a functions as a channel formation region, and the region in contact with the insulating layer 110b functions as a channel formation region. In the semiconductor layer 108, the region in contact with the insulating layer 110a preferably has higher resistance than the region in contact with the conductive layer 103 and lower resistance than the region in contact with the insulating layer 110b. − Type area, or n − It can be called an area.

[0069] FIG. 1B illustrates an example in which an edge of the semiconductor layer 108 is in contact with the top surface of the conductive layer 112b. That is, the transistor of one embodiment of the present invention is preferably a bottom-contact type. This allows the semiconductor layer 108 to be formed after the conductive layer 112b is formed (for example, after processing a film to be the conductive layer 112b or after forming the opening 143), thereby preventing damage to the semiconductor layer 108. Furthermore, this is preferable because the step of forming the opening 143 and the step of forming the opening 141 can be performed in succession (without an intervening film formation step). Note that the transistor of one embodiment of the present invention may be a top-contact type. Specifically, the conductive layer 112b may cover the edge of the semiconductor layer 108, and the edge of the semiconductor layer 108 may be in contact with the insulating layer 110 (see the transistor 100E ( FIG. 8B , etc.) described later).

[0070] The insulating layer 106 is located over the insulating layer 110, the semiconductor layer 108, and the conductive layer 112b. The insulating layer 106 is provided along the sidewalls of the openings 148, 141, and 143, with the semiconductor layer 108 interposed therebetween. The insulating layer 106 functions as a gate insulating layer.

[0071] The conductive layer 104 is located over the insulating layer 106. The conductive layer 104 overlaps with the semiconductor layer 108 with the insulating layer 106 interposed therebetween at a position overlapping with the opening 148, the opening 141, and the opening 143. The conductive layer 104 functions as a gate electrode of a transistor.

[0072] The semiconductor layer 108 has a region (offset region) that is farther from the gate than the channel formation region and to which the gate electric field is less likely to be applied. Specifically, inside the openings 141 and 148, a portion of the semiconductor layer 108 located below the bottom surface of the conductive layer 104 (toward the conductive layer 112a) is farther from the conductive layer 104 than the thickness of the insulating layer 106, and is therefore a region to which the gate electric field is less likely to be applied. The conductive layer 103 is preferably provided so as to be in contact with the offset region.

[0073] High resistance in the offset region may reduce the field-effect mobility of the transistor 100. By providing the conductive layer 103 in contact with the semiconductor layer 108, the resistance of the region of the semiconductor layer 108 that is in contact with the conductive layer 103 and its vicinity can be reduced (see two regions 108n in FIG. 2B ). This can suppress a reduction in field-effect mobility due to the offset region.

[0074] When the conductive layer 103 and the semiconductor layer 108 are in contact with each other, the conductive layer 103 extracts oxygen contained in the semiconductor layer 108 due to heat applied during the manufacturing process of the transistor 100, which makes it easy to form oxygen vacancies in the semiconductor layer 108. When impurities such as hydrogen enter the oxygen vacancies, the impurities function as donors and the carrier concentration is easily increased. Therefore, the region of the semiconductor layer 108 that is in contact with the conductive layer 103 and its vicinity can be made into a low-resistance region.

[0075] In the transistor 100, a low-resistance region in contact with the conductive layer 103 is provided in the semiconductor layer 108 between a region in contact with the conductive layer 112a and a region in contact with the insulating layer 110c, which is an i-type region. When the conductive layer 112a functions as a drain electrode and the conductive layer 112b functions as a source electrode, the semiconductor layer 108 can be said to have a low-resistance region between the region in contact with the drain electrode and the channel formation region. This makes it difficult for a high electric field to be generated near the drain region, thereby suppressing the generation of hot carriers and preventing deterioration of the transistor.

[0076] 1B , the shortest distance T1 from the top surface of the conductive layer 112a to the portion of the semiconductor layer 108 that contacts the insulating layer 110b is longer than the shortest distance T2 from the top surface of the conductive layer 112a to the bottom surface of the conductive layer 104. In other words, in a cross-sectional view, the bottom surface of the conductive layer 104 inside the opening is located lower (closer to the substrate 102) than the portion of the insulating layer 110b that contacts the semiconductor layer 108. This ensures that a gate electric field can be applied to the channel formation region of the semiconductor layer 108, thereby improving the electrical characteristics of the transistor.

[0077] It can be said that the shortest distance T1 is determined by the sum of the thickness of the conductive layer 103 and the thickness of the insulating layer 110a, and the shortest distance T2 is determined by the sum of the thickness of the semiconductor layer 108 and the thickness of the insulating layer 106. Therefore, it can be said that the sum of the thickness of the conductive layer 103 and the thickness of the insulating layer 110a is preferably greater than the sum of the thickness of the semiconductor layer 108 and the thickness of the insulating layer 106. The shortest distance T1 is preferably 0.5 times or more, more preferably 1.0 times or more, and even more preferably more than 1.0 times the shortest distance T2.

[0078] The transistor 100 includes a semiconductor layer 108 in contact with the conductive layer 103 and the insulating layer 110, and a channel formation region in the semiconductor layer 108 is located in a position where a gate electric field is sufficiently applied. In addition, the offset region in the semiconductor layer 108 has low resistance. Therefore, in the transistor 100, a decrease in field-effect mobility is suppressed, and favorable electrical characteristics can be obtained.

[0079] In the transistor of one embodiment of the present invention, the source electrode and the drain electrode are located at different heights, so that a current flows from top to bottom or from bottom to top through the semiconductor layer. In other words, it can be said that the channel length direction has a component in the height direction (vertical direction). Therefore, the transistor of one embodiment of the present invention can also be called a vertical transistor, a vertical-channel transistor, a vertical-channel transistor, or the like.

[0080] In the transistor of one embodiment of the present invention, a source electrode, a semiconductor layer, and a drain electrode can be provided so as to overlap with each other; therefore, the area occupied by the transistor can be significantly reduced compared to a so-called planar transistor in which a semiconductor layer is arranged in a planar shape.

[0081] The conductive layers 112a, 112b, 103, and 104 can each function as wirings, and the transistor 100 can be provided in a region where these wirings overlap. That is, in a circuit including the transistor 100 and the wirings, the area occupied by the transistor 100 and the wirings can be reduced. Therefore, the area occupied by the circuit can be reduced, and a small-sized semiconductor device can be provided.

[0082] For example, when the semiconductor device of one embodiment of the present invention is applied to a pixel circuit of a display device, the area occupied by the pixel circuit can be reduced, and a high-resolution display device can be obtained.Furthermore, when the semiconductor device of one embodiment of the present invention is applied to a driver circuit of a display device (for example, one or both of a gate line driver circuit and a source line driver circuit), the area occupied by the driver circuit can be reduced, and a display device with a narrow frame can be obtained.

[0083] The top surface shapes of openings 141, 143, and 148 are not limited and may be, for example, a circle, an ellipse, a triangle, a quadrangle (including a rectangle, a diamond, and a square), a pentagon, a star-shaped polygon, or any other polygon with rounded corners. The polygon may be either a concave polygon (a polygon with at least one interior angle exceeding 180 degrees) or a convex polygon (a polygon with all interior angles less than 180 degrees). As shown in FIG. 1A and other figures, the top surface shapes of openings 141, 143, and 148 are preferably circular. By making the top surface shapes of the openings circular, processing accuracy during opening formation can be improved, allowing for the formation of fine-sized openings. Note that, in this specification and the like, "circular" is not limited to a perfect circle. Note that, in this specification and the like, "top surface shape" refers to the shape in a planar view.

[0084] In this specification and the like, the top surface shape of opening 141 refers to the shape of the top surface end portion of insulating layer 110 on the opening 141 side. The top surface shape of opening 143 refers to the shape of the bottom surface end portion of conductive layer 112b on the opening 143 side. The top surface shape of opening 148 refers to the shape of the top end or bottom surface end portion of conductive layer 103 on the opening 148 side.

[0085] 1A and other figures, the top surface shapes of openings 141 and 143 can be made to match or approximately match each other. In this case, as shown in Figures 1B and 1C and other figures, it is preferable that the bottom surface edge of conductive layer 112b on the opening 143 side match or approximately match the top surface edge of insulating layer 110 on the opening 141 side. The bottom surface of conductive layer 112b refers to the surface on the insulating layer 110 side. The top surface of insulating layer 110 refers to the surface on the conductive layer 112b side.

[0086] The top shapes of the openings 141 and 143 do not have to be identical to each other (see the transistor 100C ( FIG. 6A , etc.) described later). When the top shapes of the openings 141 and 143 are circular, the openings 141 and 143 may or may not be concentric.

[0087] 1A and other figures, the top shapes of openings 141 and 148 can be made to match or approximately match each other. In this case, as shown in Figures 1B and 1C and other figures, it is preferable that the top edge of conductive layer 103 on the opening 148 side match or approximately match the bottom edge of insulating layer 110 on the opening 141 side. The top surface of conductive layer 103 refers to the surface on the insulating layer 110 side. The bottom surface of insulating layer 110 refers to the surface on the conductive layer 103 side.

[0088] The top surface shapes of the openings 141 and 148 do not have to match each other.

[0089] 3B shows an example in which opening 148 is wider than opening 141. For example, even when opening 141 and opening 148 are formed using the same resist mask, part of conductive layer 103 below the edge of insulating layer 110 may be lost due to side etching. Note that in order to form semiconductor layer 108 with good coverage along the sidewall of the opening, it is preferable to form semiconductor layer 108 by ALD.

[0090] 3C shows an example in which the opening 148 is narrower than the opening 141. For example, the opening 148 may be provided in the conductive layer 103 before a film that becomes the insulating layer 110a is formed. The opening 141 and the opening 148 may be formed using different resist masks.

[0091] In the configurations shown in FIGS. 3B and 3C, the region of the semiconductor layer 108 that is in contact with the conductive layer 103 is wider than in the configuration shown in FIG. 1B, and the low-resistance region can be wider.

[0092] The channel length, channel width, and the like of the transistor 100 will be described with reference to FIGS. 2A and 2B.

[0093] 2B, the channel length L100 of the transistor 100 is indicated by a dashed double-headed arrow. The channel length L100 can be considered to be the shortest distance between the portion of the semiconductor layer 108 that contacts the insulating layer 110a and the portion that contacts the insulating layer 110c in a cross-sectional view.

[0094] The channel length L100 of the transistor 100 corresponds to the length of the side surface of the insulating layer 110b on the opening 141 side in a cross-sectional view. That is, the channel length L100 is determined by the thickness T110 of the insulating layer 110b and the angle θ110 between the side surface of the insulating layer 110b on the opening 141 side and the surface on which the insulating layer 110b is to be formed (here, the upper surface of the insulating layer 110a). Therefore, for example, the channel length L100 can be set to a value smaller than the resolution limit of the exposure equipment, thereby enabling the realization of a fine-sized transistor. Specifically, it is possible to realize a transistor with an extremely small channel length that could not be realized using conventional exposure equipment for mass production of flat panel displays (e.g., minimum line widths of approximately 2 μm or 1.5 μm). Furthermore, it is also possible to realize a transistor with a channel length of less than 10 nm without using the extremely expensive exposure equipment used in cutting-edge LSI technology.

[0095] The channel length L100 may be, for example, 5 nm or more, 7 nm or more, or 10 nm or more, and may be less than 3 μm, 2.5 μm or less, 2 μm or less, 1.5 μm or less, 1.2 μm or less, 1 μm or less, 500 nm or less, 300 nm or less, 200 nm or less, 100 nm or less, 50 nm or less, 30 nm or less, or 20 nm or less. For example, the channel length L100 may be 100 nm or more and 1 μm or less.

[0096] By reducing the channel length L100, the on-state current of the transistor 100 can be increased. By using the transistor 100, a circuit capable of high-speed operation can be manufactured. Furthermore, the area occupied by the circuit can be reduced. Therefore, a small-sized semiconductor device can be obtained. For example, when the semiconductor device of one embodiment of the present invention is applied to a large display device or a high-resolution display device, even if the number of wirings is increased, signal delay in each wiring can be reduced, and display unevenness can be suppressed. Furthermore, since the area occupied by the circuit can be reduced, the frame of the display device can be narrowed.

[0097] The channel length L100 can be controlled by adjusting the thickness T110 and angle θ110 of the insulating layer 110b. In Fig. 2B, the thickness T110 of the insulating layer 110b is indicated by a dashed double-headed arrow.

[0098] The thickness T110 of the insulating layer 110b can be, for example, 10 nm or more, 50 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, or 500 nm or more, and can be less than 3.0 μm, 2.5 μm or less, 2.0 μm or less, 1.5 μm or less, 1.2 μm or less, or 1.0 μm or less.

[0099] The side surface of the insulating layer 110b on the opening 141 side is preferably tapered. The angle θ110 formed between the side surface of the insulating layer 110b on the opening 141 side and the surface on which the insulating layer 110b is to be formed (here, the top surface of the insulating layer 110a) is preferably 90 degrees or less. By reducing the angle θ110, the coverage of a layer (e.g., the semiconductor layer 108) provided on the insulating layer 110b can be improved. Furthermore, the smaller the angle θ110, the longer the channel length L100 can be, and the larger the angle θ110, the shorter the channel length L100 can be.

[0100] The angle θ110 may be, for example, 30 degrees or more, 35 degrees or more, 40 degrees or more, 45 degrees or more, 50 degrees or more, 55 degrees or more, 60 degrees or more, 65 degrees or more, or 70 degrees or more, and may be 90 degrees or less, 85 degrees or less, or 80 degrees or less. The angle θ110 may also be 75 degrees or less, 70 degrees or less, 65 degrees or less, or 60 degrees or less.

[0101] When the angle θ110 is 80 degrees or more and 90 degrees or less, it is preferable to form a film covering the insulating layer 110 using a film formation method with high coverage. For example, it is preferable to form the conductive layer 104 by a CVD method, and the insulating layer 106 and the semiconductor layer 108 by an ALD method. It is also preferable to form the conductive layer 104, the insulating layer 106, and the semiconductor layer 108 by an ALD method. When the angle θ110 is 60 degrees or more and 85 degrees or less, it is also possible to form a film covering the insulating layer 110 using a film formation method with higher productivity. For example, it is preferable to form the semiconductor layer 108 by a sputtering method.

[0102] Although the angle θ110 is set based on the insulating layer 110b here, it may also be set based on the entire insulating layer 110. In other words, the angle θ110 may be the angle formed between the side surface of the insulating layer 110 on the opening 141 side and the surface on which the insulating layer 110 is to be formed (here, the upper surface of the conductive layer 103).

[0103] Furthermore, when the channel formation region includes the region of the semiconductor layer 108 that is in contact with the insulating layer 110a and the region that is in contact with the insulating layer 110c, the channel length L100 can be said to be the shortest distance between the portion of the semiconductor layer 108 that is in contact with the conductive layer 103 and the portion that is in contact with the conductive layer 112b in a cross-sectional view. The channel length L100 corresponds to the length of the side surface of the entire insulating layer 110 on the opening 141 side in a cross-sectional view.

[0104] 2A and 2B, the diameter D143 of the opening 143 is indicated by a two-dot chain line with a double arrow. FIG. 2A shows an example in which the top surface shape of the openings 141, 143, and 148 is a circle with a diameter D143. In this case, the channel width W of the transistor 100 is equal to the circumferential length of the circle. In other words, the channel width W is π×D143. In this way, when the top surface shape of the openings 141, 143, and 148 is circular, a transistor with a smaller channel width W can be realized compared to other shapes.

[0105] The diameters of opening 141 and opening 143 may differ from each other, and the diameters of opening 141 and opening 148 may also differ from each other. Furthermore, the diameters of openings 148, 141, and 143 may each vary in the depth direction. When openings 141, 143, and 148 are collectively considered as a single opening, the diameter of the opening may be, for example, the average of three diameters: the diameter at the highest point, the diameter at the lowest point, and the diameter at the midpoint between these in a cross-sectional view of insulating layer 110 (or insulating layer 110b). Alternatively, the diameter of the opening may be, for example, any of the diameters at the highest point, the diameter at the lowest point, or the diameter at the midpoint between these in a cross-sectional view of insulating layer 110 (or insulating layer 110b).

[0106] When the opening 143 is formed using photolithography, the diameter D143 of the opening 143 is equal to or greater than the limit resolution of the exposure device. The diameter D143 can be, for example, 20 nm or more, 50 nm or more, 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, or 500 nm or more, and less than 5.0 μm, 4.5 μm or less, 4.0 μm or less, 3.5 μm or less, 3.0 μm or less, 2.5 μm or less, 2.0 μm or less, 1.5 μm or less, or 1.0 μm or less.

[0107] [Insulating Layer 110] Although the transistor 100 has an example in which the insulating layer 110 has a stacked structure of three layers, the insulating layer 110 may have a stacked structure of two layers or four or more layers.

[0108] It is preferable to use an inorganic insulating film for each layer constituting the insulating layer 110. Examples of inorganic insulating films include an oxide insulating film, a nitride insulating film, an oxynitride insulating film, and a nitride oxide insulating film. Examples of oxide insulating films include a silicon oxide film, an aluminum oxide film, a magnesium oxide film, a gallium oxide film, a germanium oxide film, a yttrium oxide film, a zirconium oxide film, a lanthanum oxide film, a neodymium oxide film, a hafnium oxide film, a tantalum oxide film, a cerium oxide film, a gallium zinc oxide film, and a hafnium aluminate film. Examples of nitride insulating films include a silicon nitride film and an aluminum nitride film. Examples of oxynitride insulating films include a silicon oxynitride film, an aluminum oxynitride film, a gallium oxynitride film, an yttrium oxynitride film, and a hafnium oxynitride film. Examples of nitride oxide insulating films include a silicon nitride oxide film and an aluminum nitride oxide film.

[0109] The insulating layer 110 has a portion in contact with the semiconductor layer 108. When an oxide semiconductor is used for the semiconductor layer 108, it is preferable to use an oxide for at least a part of the portion of the insulating layer 110 in contact with the semiconductor layer 108 in order to improve the interface characteristics between the semiconductor layer 108 and the insulating layer 110. Specifically, it is preferable to use an oxide for a portion of the insulating layer 110 in contact with a channel formation region of the semiconductor layer 108. The channel formation region is a high-resistance region with a low carrier concentration. It can be said that the channel formation region is i-type (intrinsic) or substantially i-type.

[0110] A layer containing oxygen is preferably used for the insulating layer 110b in contact with the channel formation region of the semiconductor layer 108. The insulating layer 110b preferably has a region with a higher oxygen content than the insulating layer 110a and the insulating layer 110c.

[0111] The insulating layer 110b is preferably formed using one or more of the above-described oxide insulating film and oxynitride insulating film. Specifically, the insulating layer 110b is preferably formed using one or both of a silicon oxide film and a silicon oxynitride film. When the insulating layer 110b contains a large amount of oxygen, it becomes easy to form an i-type region in the region of the semiconductor layer 108 that is in contact with the insulating layer 110b and in the vicinity thereof.

[0112] It is more preferable to use a film that releases oxygen when heated for the insulating layer 110b. The insulating layer 110b releases oxygen due to heat applied during the manufacturing process of the transistor 100, thereby supplying oxygen to the semiconductor layer 108. By supplying oxygen from the insulating layer 110b to the semiconductor layer 108, particularly to the channel formation region of the semiconductor layer 108, oxygen vacancies in the semiconductor layer 108 can be reduced, and a highly reliable transistor can be obtained that exhibits favorable electrical characteristics.

[0113] For example, oxygen can be supplied to the insulating layer 110b by heat treatment in an oxygen-containing atmosphere or plasma treatment in an oxygen-containing atmosphere. Alternatively, oxygen may be supplied to the insulating layer 110b by forming an oxide film on the top surface of the insulating layer 110b by a sputtering method in an oxygen atmosphere. Then, the oxide film may be removed.

[0114] The insulating layer 110b is preferably formed by a deposition method such as a sputtering method or a plasma-enhanced chemical vapor deposition (PECVD) method. In particular, the sputtering method does not require the use of hydrogen gas as a deposition gas, and therefore a film with an extremely low hydrogen content can be obtained. Therefore, supply of hydrogen to the semiconductor layer 108 can be suppressed, and the electrical characteristics of the transistor 100 can be stabilized.

[0115] It is preferable to use a film through which oxygen does not easily diffuse for each of the insulating layers 110a and 110c. This prevents oxygen contained in the insulating layer 110b from permeating to the substrate 102 side through the insulating layer 110a and from permeating to the conductive layer 112b side through the insulating layer 110c due to heating. In other words, by sandwiching the insulating layer 110b between the insulating layers 110a and 110c, through which oxygen does not easily diffuse, the oxygen contained in the insulating layer 110b can be confined. This allows oxygen to be effectively supplied to the semiconductor layer 108.

[0116] Furthermore, it is preferable to use a film through which hydrogen does not easily diffuse for each of the insulating layer 110a and the insulating layer 110c. This can prevent hydrogen from diffusing from the outside of the transistor to the semiconductor layer 108 through the insulating layer 110a or the insulating layer 110c. Similarly, it can prevent hydrogen from diffusing from the conductive layer 103 to the channel formation region of the semiconductor layer 108 through the insulating layer 110a.

[0117] For the insulating layer 110a and the insulating layer 110c, it is preferable to use one or more of the above-mentioned oxide insulating film, nitride insulating film, oxynitride insulating film, and nitride oxide insulating film, and it is preferable to use one or more of a silicon nitride film, a silicon nitride oxide film, a silicon oxynitride film, an aluminum oxide film, an aluminum oxynitride film, an aluminum nitride film, a hafnium oxide film, and a hafnium aluminate film.

[0118] The insulating layer 110a and the insulating layer 110c are preferably formed using one or more of the above-described nitride insulating film and nitride oxide insulating film. Specifically, the insulating layer 110a and the insulating layer 110c are preferably formed using one or both of a silicon nitride film and a silicon nitride oxide film.

[0119] The insulating layer 110a and the insulating layer 110c may be formed using, for example, a film containing aluminum. For example, an aluminum oxide film is preferably used for each of the insulating layer 110a and the insulating layer 110c. An aluminum oxide film is preferable because it can contain less hydrogen than a silicon nitride film.

[0120] Oxygen contained in the insulating layer 110b may oxidize the conductive layer 112a and the conductive layer 112b, resulting in an increase in resistance. By providing the insulating layer 110a between the insulating layer 110b and the conductive layer 112a, it is possible to prevent the conductive layer 112a from being oxidized and the resistance from increasing. Similarly, by providing the insulating layer 110c between the insulating layer 110b and the conductive layer 112b, it is possible to prevent the conductive layer 112b from being oxidized and the resistance from increasing. At the same time, the amount of oxygen supplied from the insulating layer 110b to the semiconductor layer 108 increases, thereby reducing oxygen vacancies in the semiconductor layer 108.

[0121] The thicknesses of the insulating layers 110a and 110c are preferably 5 nm or more, 10 nm or more, 20 nm or more, or 50 nm or more, and preferably 200 nm or less, 150 nm or less, or 100 nm or less. By setting the thicknesses of the insulating layers 110a and 110c within the above ranges, oxygen vacancies can be reduced in the semiconductor layer 108, particularly in the channel formation region. Note that the thicknesses of the insulating layers 110a and 110c may be equal to or different from each other.

[0122] For example, it is preferable that a silicon nitride film or an aluminum oxide film be used for the insulating layer 110a and the insulating layer 110c, and a silicon oxynitride film be used for the insulating layer 110b.

[0123] [Semiconductor Layer 108] The semiconductor material used for the semiconductor layer 108 is not particularly limited. For example, a semiconductor made of a single element or a compound semiconductor can be used. Examples of semiconductors made of a single element include silicon and germanium. Examples of compound semiconductors include gallium arsenide and silicon germanium. Other examples of compound semiconductors include organic semiconductors, nitride semiconductors, and oxide semiconductors. Note that these semiconductor materials may contain impurities as dopants.

[0124] The crystallinity of the semiconductor material used for the semiconductor layer 108 is not particularly limited, and any of an amorphous semiconductor, a single crystalline semiconductor, and a semiconductor having crystallinity other than single crystal (a microcrystalline semiconductor, a polycrystalline semiconductor, or a semiconductor having a crystalline region in part) may be used. Use of a single crystalline semiconductor or a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0125] The semiconductor layer 108 preferably includes a metal oxide (also referred to as an oxide semiconductor) that exhibits semiconductor characteristics.

[0126] The band gap of the metal oxide used for the semiconductor layer 108 is preferably 2.0 eV or more, more preferably 2.5 eV or more.

[0127] Examples of metal oxides that can be used for the semiconductor layer 108 include indium oxide, gallium oxide, and zinc oxide. The metal oxide preferably contains at least indium or zinc. The metal oxide preferably contains two or three elements selected from indium, element M, and zinc. The element M is a metal element or a metalloid element having a high bond energy with oxygen, such as a metal element or a metalloid element having a bond energy with oxygen higher than that of indium. Specific examples of the element M include aluminum, gallium, tin, yttrium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zirconium, molybdenum, hafnium, tantalum, tungsten, lanthanum, cerium, neodymium, magnesium, calcium, strontium, barium, boron, silicon, germanium, and antimony. The element M contained in the metal oxide is preferably one or more of the above elements, more preferably one or more selected from aluminum, gallium, tin, and yttrium, and even more preferably gallium. In this specification and the like, metal elements and metalloid elements may be collectively referred to as "metal elements," and the "metal elements" described in this specification and the like may include metalloid elements.

[0128] The semiconductor layer 108 may be formed of, for example, indium zinc oxide (In-Zn oxide, also referred to as IZO (registered trademark)), indium tin oxide (In-Sn oxide), indium titanium oxide (In-Ti oxide), indium gallium oxide (In-Ga oxide), indium gallium aluminum oxide (In-Ga-Al oxide), indium gallium tin oxide (In-Ga-Sn oxide), gallium zinc oxide (Ga-Zn oxide, also referred to as GZO), aluminum zinc oxide (Al-Zn oxide, also referred to as AZO), or indium aluminum zinc oxide. Examples of usable materials include In-Al-Zn oxide (also referred to as IAZO), indium tin zinc oxide (In-Sn-Zn oxide, also referred to as ITZO (registered trademark)), indium titanium zinc oxide (In-Ti-Zn oxide), indium gallium zinc oxide (In-Ga-Zn oxide, also referred to as IGZO), indium gallium tin zinc oxide (In-Ga-Sn-Zn oxide, also referred to as IGZTO), and indium gallium aluminum zinc oxide (In-Ga-Al-Zn oxide, also referred to as IGAZO, IGZAO, or IAGZO). Alternatively, examples of usable materials include indium tin oxide containing silicon, gallium tin oxide (Ga-Sn oxide), and aluminum tin oxide (Al-Sn oxide).

[0129] By increasing the ratio of the number of indium atoms to the total number of atoms of all metal elements contained in the metal oxide, the field-effect mobility of the transistor can be increased, and a transistor with a large on-state current can be realized.

[0130] Note that the metal oxide may contain one or more metal elements having a higher period number in the periodic table instead of or in addition to indium. The greater the overlap of the orbitals of metal elements, the greater the carrier conduction in the metal oxide. Therefore, including a metal element having a higher period number in the periodic table may improve the field-effect mobility of a transistor. Examples of metal elements having a higher period number in the periodic table include metal elements belonging to the fifth period and the sixth period. Specific examples of such metal elements include yttrium, zirconium, silver, cadmium, tin, antimony, barium, lead, bismuth, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, and europium. Lanthanum, cerium, praseodymium, neodymium, promethium, samarium, and europium are called light rare earth elements.

[0131] The metal oxide may also contain one or more nonmetallic elements. The presence of a nonmetallic element in the metal oxide may increase the carrier concentration or narrow the band gap, thereby increasing the field-effect mobility of the transistor. Examples of nonmetallic elements include carbon, nitrogen, phosphorus, sulfur, selenium, fluorine, chlorine, bromine, and hydrogen.

[0132] Furthermore, by increasing the ratio of the number of zinc atoms to the sum of the numbers of atoms of all metal elements contained in the metal oxide, the metal oxide can be made highly crystalline, and the diffusion of impurities in the metal oxide can be suppressed, thereby suppressing fluctuations in the electrical characteristics of the transistor and improving its reliability.

[0133] Furthermore, by increasing the ratio of the number of atoms of element M to the sum of the numbers of atoms of all metal elements contained in the metal oxide, the formation of oxygen vacancies in the metal oxide can be suppressed. Therefore, carrier generation due to oxygen vacancies can be suppressed, and a transistor with a small off-state current can be obtained. Furthermore, fluctuations in the electrical characteristics of the transistor can be suppressed, and reliability can be improved.

[0134] The electrical characteristics and reliability of a transistor vary depending on the composition of the metal oxide used in the semiconductor layer 108. Therefore, by varying the composition of the metal oxide depending on the electrical characteristics and reliability required of the transistor, a semiconductor device that has both excellent electrical characteristics and high reliability can be obtained.

[0135] When the metal oxide is an In-M-Zn oxide, the atomic ratio of In in the In-M-Zn oxide is preferably equal to or greater than the atomic ratio of M. Examples of atomic ratios of metal elements in such In-M-Zn oxides include In:M:Zn = 1:1:1, In:M:Zn = 1:1:1.2, In:M:Zn = 2:1:3, In:M:Zn = 3:1:1, 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 = 6:1:6, In:M:Zn = 5:2:5, and compositions in the vicinity thereof. Note that the term "nearby composition" includes a range of ±30% of the desired atomic ratio. By increasing the atomic ratio of indium in the metal oxide, the on-state current, field-effect mobility, and the like of the transistor can be increased.

[0136] Furthermore, the atomic ratio of In in the In-M-Zn oxide may be less than the atomic ratio of M. Examples of atomic ratios of metal elements in such In-M-Zn oxide include In:M:Zn=1:3:2, In:M:Zn=1:3:3, In:M:Zn=1:3:4, and compositions close to these. By increasing the proportion of M atoms in the metal oxide, the generation of oxygen vacancies can be suppressed.

[0137] When the element M contains a plurality of metal elements, the total proportion of the number of atoms of the metal elements can be used as the proportion of the number of atoms of the element M.

[0138] In this specification and the like, the ratio of the number of indium atoms to the sum of the numbers of atoms of all contained metal elements may be referred to as the indium content. The same applies to other metal elements.

[0139] The metal oxide can be preferably formed by sputtering or atomic layer deposition (ALD). When the metal oxide is formed by sputtering, the composition of the metal oxide after film formation may differ from the composition of the target. In particular, the zinc content in the metal oxide after film formation may decrease to about 50% compared to the target.

[0140] The semiconductor layer 108 may have a stacked structure including two or more metal oxide layers. The two or more metal oxide layers included in the semiconductor layer 108 may have the same or approximately the same composition. By using a stacked structure of metal oxide layers having the same composition, for example, the same sputtering target can be used for formation, thereby reducing manufacturing costs.

[0141] The two or more metal oxide layers included in the semiconductor layer 108 may have different compositions. For example, a stacked structure including a first metal oxide layer having an atomic ratio of In:M:Zn=1:3:4 or a similar composition and a second metal oxide layer having an atomic ratio of In:M:Zn=1:1:1 or a similar composition provided on the first metal oxide layer can be preferably used. Furthermore, it is particularly preferable to use gallium, aluminum, or tin as the element M. The element M in the first metal oxide layer and the second metal oxide layer may be the same or different from each other. For example, the first metal oxide layer and the second metal oxide layer may be IGZO layers having different compositions.

[0142] Also, for example, a stacked structure of a first metal oxide layer having a composition of In:Zn=4:1 (atomic ratio) or a composition close thereto and a second metal oxide layer having a composition of In:M:Zn=1:1:1 (atomic ratio) or a composition close thereto provided on the first metal oxide layer can be suitably used.

[0143] Alternatively, for example, a stacked structure of any one selected from indium oxide, indium gallium oxide, and IGZO and any one selected from IAZO, IAGZO, and ITZO (registered trademark) may be used.

[0144] The semiconductor layer 108 preferably includes a crystalline metal oxide layer. Examples of the structure of a crystalline metal oxide include a c-axis aligned crystal (CAAC) structure, a polycrystalline structure, and a nanocrystalline (nc) structure. By using a crystalline metal oxide layer for the semiconductor layer 108, the density of defect states in the semiconductor layer 108 can be reduced, and a highly reliable semiconductor device can be realized.

[0145] The higher the crystallinity of the metal oxide layer used for the semiconductor layer 108, the more the density of defect states in the semiconductor layer 108 can be reduced. On the other hand, by using a metal oxide layer with low crystallinity, a transistor capable of passing a large current can be realized.

[0146] The higher the substrate temperature (stage temperature) during the formation of the metal oxide layer, the higher the crystallinity of the formed metal oxide layer.Furthermore, the higher the ratio of the flow rate of oxygen gas to the total film formation gas used during the formation (hereinafter also referred to as oxygen flow rate ratio), the higher the crystallinity of the formed metal oxide layer.

[0147] The semiconductor layer 108 may have a stacked structure of two or more metal oxide layers with different crystallinity. For example, the semiconductor layer 108 may have a stacked structure of a first metal oxide layer and a second metal oxide layer provided on the first metal oxide layer, and the second metal oxide layer may have a region with higher crystallinity than the first metal oxide layer. Alternatively, the second metal oxide layer may have a region with lower crystallinity than the first metal oxide layer. In this case, the first metal oxide layer and the second metal oxide layer may have different compositions or may have the same or approximately the same composition.

[0148] The thickness of the semiconductor layer 108 is preferably 3 nm to 200 nm, more preferably 3 nm to 100 nm, further preferably 5 nm to 100 nm, further preferably 10 nm to 100 nm, further preferably 10 nm to 70 nm, further preferably 15 nm to 70 nm, further preferably 15 nm to 50 nm, and further preferably 20 nm to 50 nm.

[0149] When an oxide semiconductor is used for the semiconductor layer 108, hydrogen contained in the oxide semiconductor reacts with oxygen that is bonded to a metal atom to form water, and oxygen vacancies (V Ｏ In addition, defects in which hydrogen enters oxygen vacancies (hereinafter referred to as V Ｏ Hydrogen atoms (H) may function as donors and generate electrons as carriers. Furthermore, some of the hydrogen atoms may bond with oxygen atoms that are bonded to metal atoms to generate electrons as carriers. Therefore, a transistor using an oxide semiconductor containing a large amount of hydrogen is likely to have normally-on characteristics. Furthermore, hydrogen in an oxide semiconductor is easily moved by stresses such as heat and an electric field. Therefore, if an oxide semiconductor contains a large amount of hydrogen, the reliability of the transistor may be reduced.

[0150] When an oxide semiconductor is used for the semiconductor layer 108, V in the semiconductor layer 108 Ｏ It is preferable to reduce H as much as possible to obtain high-purity intrinsic or substantially high-purity intrinsic. Ｏ To obtain an oxide semiconductor in which H is sufficiently reduced, it is important to remove impurities such as water and hydrogen from the oxide semiconductor (sometimes referred to as dehydration or dehydrogenation treatment) and to supply oxygen to the oxide semiconductor to repair oxygen vacancies. Ｏ Stable electrical characteristics can be obtained by using an oxide semiconductor in which impurities such as H are sufficiently reduced for a channel formation region of a transistor. Note that supplying oxygen to an oxide semiconductor to repair oxygen vacancies is sometimes referred to as oxygen-adding treatment.

[0151] In the case where an oxide semiconductor is used for the semiconductor layer 108, the carrier concentration of the oxide semiconductor in a region functioning as a channel formation region is 1×10 １８ cm −３ Preferably, it is 1×10 or less. １７ cm −３ More preferably, it is less than 1×10 １６ cm −３ More preferably, it is less than 1×10 １３ cm −３ More preferably, it is less than 1×10 １２ cm −３The lower limit of the carrier concentration of the oxide semiconductor in the region functioning as a channel formation region is not particularly limited, but is preferably, for example, 1×10 −９ cm −３ It can be said that:

[0152] A transistor using an oxide semiconductor (hereinafter referred to as an OS transistor) has extremely high field-effect mobility compared to a transistor using amorphous silicon. Furthermore, an OS transistor has an extremely low off-state current and can hold charge accumulated in a capacitor connected in series with the transistor for a long period of time. Furthermore, the use of an OS transistor can reduce the power consumption of a semiconductor device.

[0153] OS transistors exhibit little change in electrical characteristics due to radiation exposure, i.e., have high radiation resistance, and therefore can be suitably used in environments where radiation may be incident. It can also be said that OS transistors have high reliability against radiation. For example, OS transistors can be suitably used in pixel circuits of X-ray flat panel detectors. Furthermore, OS transistors can be suitably used in semiconductor devices used in outer space. Examples of radiation include electromagnetic radiation (e.g., X-rays and gamma rays) and particle radiation (e.g., alpha rays, beta rays, proton rays, and neutron rays).

[0154] Examples of silicon that can be used for the semiconductor layer 108 include single crystal silicon, polycrystalline silicon, microcrystalline silicon, and amorphous silicon. Examples of polycrystalline silicon include low temperature polysilicon (LTPS).

[0155] A transistor using amorphous silicon for the semiconductor layer 108 can be formed over a large glass substrate and can be manufactured at low cost. A transistor using polycrystalline silicon for the semiconductor layer 108 has high field-effect mobility and can operate at high speed. A transistor using microcrystalline silicon for the semiconductor layer 108 has higher field-effect mobility and can operate at high speed than a transistor using amorphous silicon.

[0156] The semiconductor layer 108 may include a layered material that functions as a semiconductor. A layered material is a general term for a group of materials that have a layered crystal structure. A layered crystal structure is a structure in which layers formed by covalent bonds or ionic bonds are stacked via bonds weaker than covalent bonds or ionic bonds, such as van der Waals bonds. A layered material has high electrical conductivity within a unit layer, that is, high two-dimensional electrical conductivity. By using a material that functions as a semiconductor and has high two-dimensional electrical conductivity in the channel formation region, a transistor with a large on-state current can be provided.

[0157] Examples of the layered material include graphene, silicene, and chalcogenides. Chalcogenides are compounds containing chalcogen (an element belonging to Group 16). Examples of chalcogenides include transition metal chalcogenides and Group 13 chalcogenides. Specific examples of transition metal chalcogenides that can be used as semiconductor layers of transistors include molybdenum sulfide (typically MoS ２ ), molybdenum selenide (typically MoSe ２ ), molybdenum telluride (typically MoTe ２ ), tungsten sulfide (typically WS ２ ), tungsten selenide (typically WSe ２ ), tungsten tellurium (typically WTe ２ ), hafnium sulfide (typically HfS ２ ), hafnium selenide (typically HfSe ２ ), zirconium sulfide (typically ZrS ２ ), zirconium selenide (typically ZrSe ２ ) etc.

[0158] [Conductive Layer 112a, Conductive Layer 112b, Conductive Layer 103, Conductive Layer 104] The conductive layers 112a, 112b, 103, and 104 may each have a single-layer structure or a stacked structure of two or more layers. Materials that can be used for the conductive layers 112a, 112b, 103, and 104 include, for example, one or more of chromium, copper, aluminum, gold, silver, zinc, tantalum, titanium, tungsten, manganese, nickel, iron, cobalt, molybdenum, and niobium, as well as alloys containing one or more of the above metals. Low-resistance conductive materials containing one or more of copper, silver, gold, and aluminum can be preferably used for the conductive layers 112a, 112b, 103, and 104, respectively. Copper and aluminum are particularly preferred because of their excellent mass productivity.

[0159] The conductive layer 112a, the conductive layer 112b, and the conductive layer 104 can each be formed using a conductive metal oxide (also referred to as an oxide conductor). Examples of oxide conductors (OC) include indium oxide, zinc oxide, In—Sn oxide (ITO), In—Zn oxide, In—W oxide, In—W—Zn oxide, In—Ti oxide, In—Ti—Sn oxide, In—Sn—Si oxide (also referred to as ITO containing silicon, ITSO), zinc oxide to which gallium is added, and In—Ga—Zn oxide. In particular, conductive oxides containing indium are preferable because of their high conductivity.

[0160] When oxygen vacancies are formed in a metal oxide having semiconductor properties and hydrogen is added to the oxygen vacancies, a donor level is formed near the conduction band. As a result, the metal oxide becomes electrically conductive, and the conductivity of the metal oxide increases. The metal oxide that has become electrically conductive can be called an oxide conductor.

[0161] The conductive layers 112a, 112b, and 104 may each have a stacked structure of a conductive film containing the oxide conductor (metal oxide) and a conductive film containing a metal or an alloy. By using a conductive film containing a metal or an alloy, wiring resistance can be reduced.

[0162] A Cu-X alloy film (X is Mn, Ni, Cr, Fe, Co, Mo, Ta, or Ti) may be applied to each of the conductive layer 112a, the conductive layer 112b, the conductive layer 103, and the conductive layer 104. By using a Cu-X alloy film, it can be processed by a wet etching process, thereby reducing manufacturing costs.

[0163] Note that the conductive layers 112a, 112b, 103, and 104 may all be formed using the same material, or at least one of them may be formed using a different material.

[0164] The conductive layer 112a and the conductive layer 112b each have a portion in contact with the semiconductor layer 108. When an oxide semiconductor is used for the semiconductor layer 108, if an easily oxidized metal such as aluminum is used for the conductive layer 112a or the conductive layer 112b, an insulating oxide (e.g., aluminum oxide) may be formed between the conductive layer 112a or the conductive layer 112b and the semiconductor layer 108, which may hinder conduction therebetween. Therefore, for the conductive layer 112a and the conductive layer 112b, a conductive material that is not easily oxidized, a conductive material that maintains low electrical resistance even when oxidized, or a conductive oxide material is preferably used.

[0165] For the conductive layer 112a and the conductive layer 112b, it is preferable to use, for example, titanium, tantalum nitride, titanium nitride, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, or an oxide containing lanthanum and nickel. These are preferable because they are conductive materials that are resistant to oxidation or materials that maintain conductivity even when oxidized. Note that when the conductive layer 112a or the conductive layer 112b has a stacked structure, it is preferable to use a conductive material that is resistant to oxidation for at least the layer in contact with the semiconductor layer 108.

[0166] The conductive layer 112 a and the conductive layer 112 b can each be formed using any of the above-described oxide conductors. Specifically, conductive oxides such as indium oxide, zinc oxide, ITO, In—Zn oxide, In—W oxide, In—W—Zn oxide, In—Ti oxide, In—Ti—Sn oxide, In—Sn oxide containing silicon, and zinc oxide doped with gallium can be used.

[0167] The conductive layer 112a and the conductive layer 112b may each be made of a nitride conductor, such as tantalum nitride or titanium nitride.

[0168] For example, the conductive layer 112a and the conductive layer 112b can each have a single-layer structure of an oxide conductor film, a stacked structure of a metal film and an oxide conductor film, or a stacked structure of a metal film. Examples of oxide conductor films include an ITSO film. Examples of metal films include a single-layer structure of a tungsten film, a single-layer structure of a titanium film, a single-layer structure of a copper film, and a three-layer structure of a titanium film, an aluminum film, and a titanium film.

[0169] The conductive layer 103 is preferably made of a material having higher conductivity than the conductive layer 112a, which allows the conductive layer 103 to effectively function as an auxiliary wiring for the conductive layer 112a. The conductive layer 103 can be made of, for example, one or more of copper, aluminum, titanium, tungsten, and molybdenum, or an alloy containing one or more of the above-mentioned metals.

[0170] For example, an ITSO film is preferably used for the conductive layer 112a and the conductive layer 112b. For example, a titanium film is preferably used for the conductive layer 103. For example, a three-layer structure of a titanium film, an aluminum film, and another titanium film is preferably used for the conductive layer 104.

[0171] [Insulating Layer 106] The insulating layer 106 may have a single-layer structure or a stacked structure of two or more layers. The insulating layer 106 preferably has one or more inorganic insulating films. Examples of inorganic insulating films include an insulating oxide film, an insulating nitride film, an insulating oxynitride film, and an insulating nitride oxide film. Specific examples of these inorganic insulating films are as described above.

[0172] The insulating layer 106 has a portion in contact with the semiconductor layer 108. When an oxide semiconductor is used for the semiconductor layer 108, it is preferable to use any one of the above-described oxide insulating film and oxynitride insulating film for at least a film that is in contact with the semiconductor layer 108 among films that form the insulating layer 106. It is more preferable to use a film that releases oxygen by heating for the insulating layer 106.

[0173] Specifically, when the insulating layer 106 has a single-layer structure, it is preferable to use a silicon oxide film or a silicon oxynitride film for the insulating layer 106 .

[0174] The insulating layer 106 can have a stacked-layer structure of an oxide insulating film or an oxynitride insulating film on a side in contact with the semiconductor layer 108 and a nitride insulating film or a nitride oxide insulating film on a side in contact with the conductive layer 104. As the oxide insulating film or the oxynitride insulating film, for example, a silicon oxide film or a silicon oxynitride film is preferably used. As the nitride insulating film or the nitride oxide insulating film, a silicon nitride film or a silicon nitride oxide film is preferably used.

[0175] A silicon nitride film and a silicon nitride oxide film have characteristics of releasing little impurities (for example, water and hydrogen) from themselves and being difficult for oxygen and hydrogen to permeate, and therefore can be suitably used as the insulating layer 106. By suppressing the diffusion of impurities from the insulating layer 106 to the semiconductor layer 108, the electrical characteristics of the transistor can be improved and the reliability can be increased.

[0176] Note that in a miniaturized transistor, a thin gate insulating layer may result in a large leakage current. By using a material with a high relative dielectric constant (also referred to as a high-k material) for the gate insulating layer, a transistor can be operated at a low voltage while maintaining a physical film thickness. Examples of high-k materials that can be used for the insulating layer 106 include gallium oxide, hafnium oxide, zirconium oxide, an oxide containing aluminum and hafnium, an oxynitride containing aluminum and hafnium, an oxide containing silicon and hafnium, an oxynitride containing silicon and hafnium, and a nitride containing silicon and hafnium.

[0177] [Substrate 102] There are no significant limitations on the material of the substrate 102, but it must have at least heat resistance sufficient to withstand subsequent heat treatment. For example, the substrate 102 may be a single crystal semiconductor substrate made of silicon or silicon carbide, a polycrystalline semiconductor substrate, a compound semiconductor substrate such as silicon germanium, an SOI substrate, a glass substrate, a quartz substrate, a sapphire substrate, a ceramic substrate, or a resin substrate. A semiconductor element may be provided on the substrate 102. The semiconductor substrate and the insulating substrate may have either a circular or rectangular shape.

[0178] A flexible substrate may be used as the substrate 102, and the transistor 100 and the like may be formed directly on the flexible substrate. Alternatively, a peeling layer may be provided between the substrate 102 and the transistor 100 and the like. The peeling layer can be used to separate a semiconductor device, after a part or all of the semiconductor device is completed thereon, from the substrate 102 and transfer the semiconductor device to another substrate. In this case, the transistor 100 and the like can also be transferred to a substrate with poor heat resistance or a flexible substrate.

[0179] [Modifications of the Transistor 100] FIGS. 4 to 9 show modifications of the transistor 100. FIG.

[0180] [Transistor 100A] Fig. 4A shows a top view of the transistor 100A. Fig. 4B is a cross-sectional view taken along dashed lines A1-A2 in Fig. 4A. Fig. 4C is a cross-sectional view taken along dashed lines B1-B2 in Fig. 4A.

[0181] The transistor 100A differs from the transistor 100 in that a conductive layer 105 is provided between the insulating layer 110c and the conductive layer 112b.

[0182] The conductive layer 105 is provided over the insulating layer 110, and the conductive layer 112b is provided over the conductive layer 105. At least a part of the conductive layer 112b is in contact with a top surface of the conductive layer 105. The conductive layer 105 can function as an auxiliary wiring and / or a wiring for the conductive layer 112b. An opening 143 is provided in the conductive layer 105.

[0183] The semiconductor layer 108 is preferably in contact with the side surface of the conductive layer 105. The semiconductor layer 108 is preferably provided in contact with the end portion of the conductive layer 105 on the opening 143 side (which can also be referred to as the side wall of the opening 143).

[0184] Note that a metal oxide may be formed between the conductive layer 105 and the semiconductor layer 108. Specifically, the side surface of the conductive layer 105 at the opening 143 may be oxidized by contact with the semiconductor layer 108. Depending on the material of the conductive layer 105, the conductivity of the conductive layer 105 may be reduced by oxidation. Since the conductive layer 105 and the semiconductor layer 108 do not need to be electrically connected, the side surface of the conductive layer 105 at the opening 143 may be oxidized. For example, an oxide containing the same metal as the metal contained in the conductive layer 105 may be present between the conductive layer 105 and the semiconductor layer 108.

[0185] As described in the description of the transistor 100, when an oxide semiconductor is used for the semiconductor layer 108, a conductive layer in contact with the semiconductor layer 108 is preferably made of a material that maintains conductivity even when oxidized, such as an oxide conductor.

[0186] On the other hand, it is preferable to use a material having lower resistance than an oxide conductor, such as a metal or an alloy, for the wiring. Therefore, it is preferable to use a material having higher conductivity than the conductive layer 112b, such as a metal or an alloy, for the conductive layer 105. The conductive layer 105 can be made of any of the materials that can be used for the conductive layer 103.

[0187] In the semiconductor layer 108, a region in contact with the conductive layer 105 (or an oxide of the conductive layer 105) functions as a low-resistance region.

[0188] When the conductive layer 105 and the semiconductor layer 108 are in contact with each other, the conductive layer 105 extracts oxygen contained in the semiconductor layer 108 due to heat applied during the manufacturing process of the transistor 100A, which makes it easy to form oxygen vacancies in the semiconductor layer 108. When impurities such as hydrogen enter the oxygen vacancies, the impurities function as donors and the carrier concentration is easily increased. Therefore, the region of the semiconductor layer 108 that is in contact with the conductive layer 105 and its vicinity can be made into a low-resistance region.

[0189] In the transistor 100A, a low-resistance region in contact with the conductive layer 103 is provided in the semiconductor layer 108 between a region in contact with the conductive layer 112a and a region in contact with the insulating layer 110c, which is an i-type region. When the conductive layer 112a functions as a drain electrode and the conductive layer 112b functions as a source electrode, the semiconductor layer 108 can be said to have a low-resistance region between the region in contact with the drain electrode and the channel formation region. This makes it difficult for a high electric field to be generated near the drain region, thereby suppressing the generation of hot carriers and preventing deterioration of the transistor.

[0190] In the transistor 100A, a low-resistance region in contact with the conductive layer 105 is provided in the semiconductor layer 108 between a region in contact with the conductive layer 112b and a region in contact with the insulating layer 110c, which is an i-type region. When the conductive layer 112a functions as a source electrode and the conductive layer 112b functions as a drain electrode, the semiconductor layer 108 can be said to have a low-resistance region between the region in contact with the drain electrode and the channel formation region. This makes it difficult for a high electric field to be generated near the drain region, thereby suppressing the generation of hot carriers and preventing deterioration of the transistor.

[0191] As described above, the transistor of one embodiment of the present invention can have high reliability regardless of whether the conductive layer 112 a or the conductive layer 112 b serves as the drain electrode, which increases the degree of freedom in designing a semiconductor device.

[0192] Between the region of the semiconductor layer 108 in contact with the conductive layer 112a and the region in contact with the conductive layer 112b, a region in contact with the conductive layer 103, a region in contact with the insulating layer 110, and a region in contact with the conductive layer 105 are provided in this order. The insulating layer 110 has a three-layer structure in which the insulating layer 110b is sandwiched between the insulating layers 110a and 110c. Furthermore, the insulating layer 110 is sandwiched between the conductive layers 105 and 103. In other words, the stacked body in contact with the semiconductor layer 108 has a symmetrical structure with respect to a line perpendicular to the up-down direction (stacking direction). This allows the carrier concentration distribution in the channel length direction of the semiconductor layer 108 to be appropriate. This allows the transistor to have good electrical characteristics and high reliability.

[0193] [Transistor 100B] Fig. 5A shows a top view of the transistor 100B. Fig. 5B is a cross-sectional view taken along dashed lines A1-A2 in Fig. 5A. Fig. 5C is a cross-sectional view taken along dashed lines B1-B2 in Fig. 5A.

[0194] The transistor 100B differs from the transistor 100 in that an insulating layer 110d is provided between the insulating layer 110c and the conductive layer 112b.

[0195] The insulating layer 110d is preferably a layer that releases hydrogen when heated. The insulating layer 110d releases hydrogen due to heat applied during the manufacturing process of the transistor 100, and thus hydrogen can be supplied to the semiconductor layer 108. This allows a low-resistance region to be formed in the vicinity of a region of the semiconductor layer 108 that is in contact with the conductive layer 112b.

[0196] For example, the insulating layer 110d has a region with a higher hydrogen content than the insulating layer 110a. Furthermore, the insulating layer 110d preferably has a region with a higher hydrogen content than the insulating layer 110c.

[0197] When the insulating layer 110d is a layer with a high hydrogen content, the resistance of the region of the semiconductor layer 108 that is in contact with the insulating layer 110d and its vicinity can be reduced.

[0198] The insulating layer 110c has a lower hydrogen content than the insulating layer 110d, which can prevent hydrogen from diffusing from the insulating layer 110d to the insulating layer 110b and to a region of the semiconductor layer 108 to which a gate electric field is sufficiently applied (a region to be made i-type).

[0199] For the insulating layer 110d, it is preferable to use one or more of the above-mentioned oxide insulating film, nitride insulating film, oxynitride insulating film, and nitride oxide insulating film, and it is preferable to use one or more of a silicon nitride film, a silicon nitride oxide film, a silicon oxynitride film, an aluminum oxide film, an aluminum oxynitride film, an aluminum nitride film, a hafnium oxide film, and a hafnium aluminate film.

[0200] The insulating layer 110d is preferably formed using one or more of the above-described insulating nitride film and insulating nitride oxide film. Specifically, the insulating layer 110d is preferably formed using one or both of a silicon nitride film and a silicon nitride oxide film.

[0201] The silicon nitride film and the silicon nitride oxide film each release little impurities (e.g., water and hydrogen) from themselves and can realize films that are difficult for oxygen and hydrogen to permeate, and therefore can be suitably used as the insulating layer 110a and the insulating layer 110c. Furthermore, by changing the film formation conditions (e.g., film formation gas or power during film formation), the silicon nitride film and the silicon nitride oxide film can each be made to release a lot of hydrogen, and therefore can also be suitably used as the insulating layer 110d.

[0202] Since the hydrogen content is low compared to the main components that make up the insulating layer (for example, nitrogen and silicon in the case of a silicon nitride layer), it is preferable to compare the hydrogen content in each layer that makes up the insulating layer 110 using SIMS analysis.

[0203] Furthermore, even when insulating layers 110c and 110d are made of layers with the same main component (e.g., silicon nitride layers), they may be distinguishable by cross-sectional observation. For example, in a transmitted electron (TE) image obtained by scanning transmission electron microscopy (STEM), insulating layer 110d is observed to have higher brightness than insulating layer 110c.

[0204] In the transistor 100B, a low-resistance region in contact with the conductive layer 103 is provided in the semiconductor layer 108 between a region in contact with the conductive layer 112a and a region in contact with the insulating layer 110c, which is an i-type region. When the conductive layer 112a functions as a drain electrode and the conductive layer 112b functions as a source electrode, the semiconductor layer 108 can be said to have a low-resistance region between the region in contact with the drain electrode and the channel formation region. This makes it difficult for a high electric field to be generated near the drain region, thereby suppressing the generation of hot carriers and preventing deterioration of the transistor.

[0205] In the transistor 100B, a low-resistance region in contact with the insulating layer 110d is provided in the semiconductor layer 108 between a region in contact with the conductive layer 112b and a region in contact with the insulating layer 110c, which is an i-type region. When the conductive layer 112a functions as a source electrode and the conductive layer 112b functions as a drain electrode, the semiconductor layer 108 can be said to have a low-resistance region between the region in contact with the drain electrode and the channel formation region. This makes it difficult for a high electric field to be generated near the drain region, thereby suppressing the generation of hot carriers and preventing deterioration of the transistor.

[0206] As described above, the transistor of one embodiment of the present invention can have high reliability regardless of whether the conductive layer 112 a or the conductive layer 112 b serves as the drain electrode, which increases the degree of freedom in designing a semiconductor device.

[0207] Between the region of the semiconductor layer 108 in contact with the conductive layer 112a and the region in contact with the conductive layer 112b, there is a region in contact with the conductive layer 103 and a region in contact with the insulating layer 110. The insulating layer 110b is sandwiched between the insulating layers 110a and 110c, and this three-layer structure is sandwiched between the conductive layer 103 and the insulating layer 110d. The conductive layer 103 and the insulating layer 110d have in common the fact that they both reduce the resistance of the semiconductor layer 108. In other words, the stacked body in contact with the semiconductor layer 108 can be considered to have a symmetrical structure with respect to a line perpendicular to the vertical direction (stacking direction). This allows for an appropriate carrier concentration distribution in the channel length direction of the semiconductor layer 108. This allows for excellent electrical characteristics and high reliability in the transistor.

[0208] [Transistor 100C] Fig. 6A shows a top view of the transistor 100C. Fig. 6B shows a cross-sectional view taken along dashed dotted lines A1-A2 in Fig. 6A. Fig. 6C shows a cross-sectional view taken along dashed dotted lines B1-B2 in Fig. 6A.

[0209] The transistor 100C differs from the transistor 100 mainly in that the opening 143 is larger than the openings 141 and 148 in plan view.

[0210] The end of the conductive layer 112 b on the opening 143 side is located outside the end of the insulating layer 110 on the opening 141 side.

[0211] The semiconductor layer 108 is in contact with the top surface and side surfaces of the conductive layer 112b, the side surfaces of the insulating layer 110, the side surfaces of the conductive layer 103, and the top surface of the conductive layer 112a.

[0212] In the transistor 100C, the step on the surface on which the semiconductor layer 108 is formed is smaller than in the transistor 100, and the coverage of the semiconductor layer 108 may be improved.

[0213] [Transistor 100D] Fig. 7A shows a top view of the transistor 100D. Fig. 7B is a cross-sectional view taken along dashed dotted line A1-A2 in Fig. 7A, and Fig. 7C is a cross-sectional view taken along dashed dotted line B1-B2 in Fig. 7A.

[0214] The transistor 100D differs from the transistor 100 in that the semiconductor layer 108 is in contact with the side surface of the conductive layer 112b that does not face the opening 143 (the side opposite to the opening 143).

[0215] The top surface shapes and sizes of the semiconductor layer 108 and the conductive layer 112b are not particularly limited. The end portions of the semiconductor layer 108 may be aligned with the end portions of the conductive layer 112b, may be located inside the end portions of the conductive layer 112b, or may be located outside the end portions of the conductive layer 112b.

[0216] 7B , the semiconductor layer 108 of the transistor 100D covers the side surface of the conductive layer 112b that does not face the opening 143. An end of the semiconductor layer 108 is located outside the end of the conductive layer 112b and is in contact with the insulating layer 110. The end of the semiconductor layer 108 on the left side (B1 side) in FIG. 7C covers the end of the conductive layer 112b and is in contact with the insulating layer 110. The end of the semiconductor layer 108 on the right side (B2 side) in FIG. 7C is in contact with the conductive layer 112b.

[0217] [Transistor 100E] Fig. 8A shows a top view of the transistor 100E. Fig. 8B is a cross-sectional view taken along dashed dotted line A1-A2 in Fig. 8A, and Fig. 8C is a cross-sectional view taken along dashed dotted line B1-B2 in Fig. 8A.

[0218] The transistor 100E differs from the transistor 100 in that it is a top-contact type in which the conductive layer 112b is in contact with the top surface of the semiconductor layer 108.

[0219] As shown in FIG. 8B, the conductive layer 112b of the transistor 100E covers the top surface and side surfaces of the semiconductor layer 108 located over the insulating layer 110 (which may also be referred to as the edge portions of the semiconductor layer 108).

[0220] [Transistor 100F] FIG. 9A shows a cross-sectional view of the transistor 100F.

[0221] The transistor 100F differs from the transistor 100B in that the transistor 100F includes a conductive layer 109 functioning as a backgate electrode over the insulating layer 110a and an insulating layer 110e over the insulating layer 110a and the conductive layer 109. Note that although an example in which a backgate electrode is added to the transistor 100B is shown here, a backgate electrode can also be provided in the other transistors exemplified in this embodiment.

[0222] The conductive layer 109 is located over the insulating layer 110a. The conductive layer 109 is electrically insulated from the conductive layer 112a and the conductive layer 103 by the insulating layer 110a. An opening is provided in the conductive layer 109 at a position overlapping with the conductive layer 112a. An opening in the insulating layer 110 is present inside the opening in the conductive layer 109. This allows the conductive layer 109 and the semiconductor layer 108 to have no region in contact with each other.

[0223] The insulating layer 110 includes an insulating layer 110a on the conductive layer 103, an insulating layer 110e on the insulating layer 110a and the conductive layer 109, an insulating layer 110b on the insulating layer 110e, an insulating layer 110c on the insulating layer 110b, and an insulating layer 110d on the insulating layer 110c.

[0224] The insulating layer 110e covers the top surface and side surfaces of the conductive layer 109. The insulating layer 110e is provided so as to cover part of the opening of the conductive layer 109. The insulating layer 110e is in contact with the insulating layer 110a through the opening of the conductive layer 109.

[0225] The insulating layer 110e preferably has the same structure as the insulating layers 110a and 110c. Specifically, the insulating layer 110e preferably uses a film through which oxygen is less likely to diffuse. Also, the insulating layer 110e preferably uses a film through which hydrogen is less likely to diffuse.

[0226] In the transistor 100F, the semiconductor layer 108 has a region that overlaps with the conductive layer 104 via the insulating layer 106 and also overlaps with the conductive layer 109 via parts of the insulating layer 110 (particularly, the insulating layer 110b and the insulating layer 110e). In other words, the semiconductor layer 108 has a region that is sandwiched between the conductive layer 104 and the conductive layer 109 via the insulating layer 106 and parts of the insulating layer 110 (particularly, the insulating layer 110b and the insulating layer 110e).

[0227] The conductive layer 109 functions as a back gate electrode of the transistor 100F. Part of the insulating layer 110 functions as a back gate insulating layer of the transistor 100F.

[0228] By providing the back gate electrode in the transistor 100F, the potential of the back gate side (also referred to as a back channel) of the semiconductor layer 108 is fixed, and the saturation of the Id-Vd characteristics of the transistor 100F can be increased.

[0229] In this specification and the like, a small change in current (small gradient) in the saturation region in the Id-Vd characteristics of a transistor may be expressed as "high saturation."

[0230] Furthermore, since the transistor 100F has a back gate electrode, the potential of the back channel of the semiconductor layer 108 can be fixed. Therefore, in an n-type transistor, a negative shift in the threshold voltage can be suppressed. This allows a transistor with normally-off characteristics (i.e., a positive threshold voltage). Note that in a p-type transistor, a positive shift in the threshold voltage can be suppressed, allowing a transistor with normally-off characteristics (i.e., a negative threshold voltage).

[0231] 9A shows an example in which the thickness of the insulating layer 110a is uniform regardless of location. Note that the insulating layer 110a may have different thicknesses in regions that overlap with the conductive layer 109 and regions that do not. For example, when processing the film that will become the conductive layer 109, the regions of the insulating layer 110a that do not overlap with the conductive layer 109 may be partially removed, resulting in a thinner thickness.

[0232] At least a region of the semiconductor layer 108 that is in contact with the insulating layer 110b functions as a channel formation region. In this embodiment, the region of the semiconductor layer 108 that is in contact with the insulating layer 110e is not included in the channel formation region; however, this region may be included in the channel formation region.

[0233] 9A, the channel length L100 of the transistor 100 is indicated by a dashed double-headed arrow. The channel length L100 can be considered to be the shortest distance between the portion of the semiconductor layer 108 that contacts the insulating layer 110d and the portion that contacts the insulating layer 110e in a cross-sectional view.

[0234] As shown in FIG. 9A, the channel length L100 may be affected by the thickness T109 of the conductive layer 109 depending on the shortest distance L1 between the conductive layer 109 and the semiconductor layer 108.

[0235] The channel length L100 of the transistor corresponds to the length of the side surface of the opening of the insulating layer 110b in a cross-sectional view. When the distance between the conductive layer 109 and the semiconductor layer 108 is reduced (i.e., the distance L1 is reduced), the channel length L100 may be increased due to the influence of the thickness of the conductive layer 109. Therefore, the channel length L100 may be set to be 1 time or more, 1.5 times or more, or even 2 times or more the thickness T110.

[0236] [Transistor 100G] FIG. 9B shows a cross-sectional view of the transistor 100G.

[0237] The transistor 100G differs from the transistor 100F mainly in that the insulating layer 110 has a seven-layer structure.

[0238] The insulating layer 110 includes an insulating layer 110a on the conductive layer 103, an insulating layer 110b1 on the insulating layer 110a, an insulating layer 110e1 on the insulating layer 110b1, an insulating layer 110e2 on the insulating layer 110e1 and the conductive layer 109, an insulating layer 110b2 on the insulating layer 110e2, an insulating layer 110c on the insulating layer 110b2, and an insulating layer 110d on the insulating layer 110c.

[0239] The insulating layer 110b1 and the insulating layer 110b2 can have the same structure as that applicable to the insulating layer 110b. Specifically, the insulating layer 110b1 and the insulating layer 110b2 are preferably layers containing oxygen and preferably have a region with a higher oxygen content than at least one of the insulating layers 110a, 110c, 110d, 110e1, and 110e2.

[0240] The insulating layers 110e1 and 110e2 can have the same structure as that applicable to the insulating layer 110e. Specifically, the insulating layers 110e1 and 110e2 are preferably made of a film through which oxygen is less likely to diffuse. Furthermore, the insulating layers 110e1 and 110e2 are preferably made of a film through which hydrogen is less likely to diffuse.

[0241] The insulating layers 110a, 110c, and 110d may have the same configuration as described above.

[0242] In FIG. 9B, the channel length L100 can be said to be the shortest distance between the portion of the semiconductor layer 108 that contacts the insulating layer 110a and the portion that contacts the insulating layer 110c.

[0243] With this structure, the insulating layer 110 can be symmetrical above and below the conductive layer 109. Furthermore, oxygen can be supplied to the semiconductor layer 108 from the two insulating layers 110b1 and 110b2, which can improve the characteristics of the transistor.

[0244] 10 shows a circuit diagram of a semiconductor device of one embodiment of the present invention. 11 to 16 show top views and cross-sectional views of the semiconductor device of one embodiment of the present invention. Hereinafter, the transistor 100 will be mainly used as an example of a transistor included in the semiconductor device of one embodiment of the present invention. The semiconductor device of one embodiment of the present invention is not limited to this, and may include one or more of the above-described transistors 100A to 100G.

[0245] A semiconductor device of one embodiment of the present invention includes at least two transistors, and one of the gate, source, or drain of one transistor is electrically connected to the gate, source, or drain of another transistor.

[0246] 10A includes a transistor 100 and a transistor 200. One of the source and the drain of the transistor 200 is electrically connected to the gate of the transistor 100.

[0247] 10A to 10C, the transistors 100 and 200 are n-channel transistors; however, one embodiment of the present invention is not limited to this. One or both of the transistors 100 and 200 may be p-channel transistors.

[0248] 11A to 11C are cross-sectional views of a semiconductor device 10. The semiconductor device 10 includes a transistor 100 and a transistor 150. In the semiconductor device 10, any one of a gate, a source, and a drain of the transistor 100 can be electrically connected to any one of a gate, a source, and a drain of the transistor 150.

[0249] The transistor 100 is provided over a substrate 102. The transistor 100 has the above-described structure, and therefore detailed description thereof will be omitted (see FIGS. 1 and 2).

[0250] Note that Figure 11A corresponds to a cross-sectional view of transistor 100 and transistor 150 in the direction of dotted line A1-A2 in Figure 1A, Figure 11B is a cross-sectional view of transistor 100 between dotted line B1-B2 in Figure 1A, and Figure 11C corresponds to a cross-sectional view of transistor 150 in the same direction as Figure 11B.

[0251] The transistor 150 includes a conductive layer 112c, a conductive layer 103a, an insulating layer 110 (insulating layers 110a, 110b, and 110c), an insulating layer 110s, a semiconductor layer 108a, an insulating layer 106, a conductive layer 107a, a conductive layer 107b, and a conductive layer 104a. Each layer included in the transistor 150 may have a single-layer structure or a stacked-layer structure.

[0252] A conductive layer 112c is provided over the substrate 102, and a conductive layer 103a is provided over the conductive layer 112c. The conductive layer 112c and the conductive layer 103a function as backgate electrodes of the transistor 150. The conductive layer 112c can be formed using the same material and in the same process as the conductive layer 112a. The conductive layer 103a can be formed using the same material and in the same process as the conductive layer 103. Note that the transistor 150 does not necessarily have a backgate electrode.

[0253] An insulating layer 110 is provided to cover the conductive layer 112c and the conductive layer 103a, and an insulating layer 110s is provided over the insulating layer 110. The insulating layer 110 and the insulating layer 110s function as back-gate insulating layers of the transistor 150. The insulating layer 110s is in contact with the channel formation region of the semiconductor layer 108a, and therefore is preferably an insulating layer containing oxygen. The insulating layer 110s can be formed using, for example, a material that is suitable for the insulating layer 110b.

[0254] The semiconductor layer 108a is provided over the insulating layer 110s. The semiconductor layer 108a has a region overlapping with the conductive layers 112c and 103a with the insulating layer 110 and the insulating layer 110s interposed therebetween. The semiconductor layer 108a can be formed using the same material and in the same process as the semiconductor layer 108.

[0255] Here, the semiconductor layer 108 and the semiconductor layer 108a may be made of the same material, or different materials. Furthermore, the semiconductor layer 108 and the semiconductor layer 108a may be made of materials with different compositions. For example, the semiconductor layer 108 and the semiconductor layer 108a may both be made of In—Ga—Zn oxide with the same composition. Furthermore, both the semiconductor layer 108 and the semiconductor layer 108a may be made of In—Ga—Zn oxide, with one layer having a higher proportion of In atoms in the metal oxide than the other. Furthermore, one of the semiconductor layers 108 and 108a may be made of In—Ga—Zn oxide, and the other may be made of In—Zn oxide.

[0256] The insulating layer 106 is provided to cover the insulating layer 110s and the semiconductor layer 108a. The insulating layer 106 functions as a gate insulating layer of the transistor 150.

[0257] A conductive layer 104a is provided over the insulating layer 106. The conductive layer 104a has a region overlapping with the semiconductor layer 108a with the insulating layer 106 interposed therebetween. The conductive layer 104a functions as a gate electrode of the transistor 150. The conductive layer 104a can be formed using the same material and in the same process as the conductive layer 104.

[0258] An insulating layer 195 is provided to cover the conductive layer 104a, and the conductive layers 107a and 107b are provided over the insulating layer 195. The conductive layers 107a and 107b are in contact with the semiconductor layer 108a through openings provided in the insulating layers 106 and 195, respectively. One of the conductive layers 107a and 107b functions as a source electrode of the transistor 150, and the other functions as a drain electrode.

[0259] The insulating layer 195 functions as a protective layer. The insulating layer 195 is preferably made of a material that does not easily diffuse impurities. By providing the insulating layer 195, it is possible to effectively prevent impurities from diffusing into the transistor from the outside, thereby improving the reliability of the semiconductor device. Examples of impurities include water and hydrogen. For example, the insulating layer 195 includes one or both of an inorganic insulating layer and an organic insulating layer. The insulating layer 195 may have a stacked structure of an inorganic insulating layer and an organic insulating layer.

[0260] Examples of inorganic insulating films that can be used for the insulating layer 195 include an insulating oxide film, an insulating nitride film, an insulating oxynitride film, and an insulating nitride oxide film. Specific examples of these inorganic insulating films are as described for the insulating layer 110. More specifically, the insulating layer 195 can include one or more of silicon nitride, silicon nitride oxide, silicon oxynitride, aluminum oxide, aluminum oxynitride, aluminum nitride, hafnium oxide, and hafnium aluminate. The insulating layer 195 can include, as an organic material, one or more of an acrylic resin and a polyimide resin, for example.

[0261] 11C shows an example in which the conductive layer 104a and the conductive layer 103a are not connected. For example, a constant potential can be supplied to the back gate, and a signal for driving the transistor 150 can be supplied to the gate. In this way, the threshold voltage when driving the transistor 150 can be controlled by the potential supplied to the back gate.

[0262] The conductive layer 104a may be connected to the conductive layer 103a through an opening provided in the insulating layer 106 and the insulating layer 110. In this way, the same potential is applied to the gate and the back gate, and the current that can flow when the transistor 150 is in an on state can be increased. In addition, the current that flows when the transistor 150 is in an off state can be reduced.

[0263] Alternatively, the conductive layer 107a or the conductive layer 107b may be connected to the conductive layer 103a through an opening provided in the insulating layer 106 and the insulating layer 110. By applying the same potential to the source and the back gate, the potential of the back channel is stabilized, and the saturation of the Id-Vd characteristics of the transistor can be increased.

[0264] The transistor 150 is a so-called top-gate transistor having a gate electrode above the semiconductor layer 108a. For example, by adding an impurity element to the semiconductor layer 108a using the conductive layer 104a functioning as the gate electrode as a mask, the source and drain regions can be formed in a self-aligned manner. The transistor 150 can be called a TGSA (Top Gate Self-Aligned) transistor.

[0265] The channel length of the transistor 150 can be controlled by the width of the conductive layer 104a in the channel length direction. Therefore, the channel length of the transistor 150 is equal to or greater than the resolution limit of an exposure apparatus used to manufacture the transistor. By increasing the channel length, the transistor can have high saturation characteristics.

[0266] In manufacturing the semiconductor device 10, the transistor 100 with a short channel length and the transistor 150 with a long channel length can be formed over the same substrate by sharing some of the steps. For example, by applying the transistor 100 to a transistor that requires a large on-state current and the transistor 150 to a transistor that requires high saturation characteristics, a high-performance semiconductor device can be obtained.

[0267] [Semiconductor device 10A] Fig. 10B shows a circuit diagram of the semiconductor device 10A. Fig. 12A shows a top view of the semiconductor device 10A. Fig. 12B is a cross-sectional view taken along dashed lines A1-A2 in Fig. 12A, Fig. 13A is a cross-sectional view taken along dashed lines B1-B2 in Fig. 12A, and Fig. 13B is a cross-sectional view taken along dashed lines B3-B4 in Fig. 12A.

[0268] The semiconductor device 10A includes a transistor 100 and a transistor 200. The other of the source and the drain of the transistor 200 is electrically connected to the other of the source and the drain of the transistor 100.

[0269] The transistor 100 and the transistor 200 are each provided over a substrate 102 .

[0270] The transistor 100 has the above-described structure, and therefore detailed description thereof will be omitted (see FIGS. 1 and 2).

[0271] The transistor 200 includes a conductive layer 112c, a conductive layer 103a, a semiconductor layer 108a, a conductive layer 112b, an insulating layer 106, and a conductive layer 104a.

[0272] The conductive layer 112c functions as one of a source electrode and a drain electrode of the transistor 200. The conductive layer 112c can be formed using the same material and in the same process as the conductive layer 112a.

[0273] The semiconductor layer 108a can be formed using the same material and in the same process as the semiconductor layer 108. Alternatively, the semiconductor layer 108 and the semiconductor layer 108a may be formed using different materials and in different processes.

[0274] The conductive layer 112b functions as the other of the source electrode and the drain electrode of the transistor 100 and also functions as the other of the source electrode and the drain electrode of the transistor 200. When the conductive layer 112b is shared between the transistors 100 and 200, the area occupied by the semiconductor device can be reduced.

[0275] The conductive layer 104a functions as a gate electrode of the transistor 200. The conductive layer 104a can be formed using the same material and in the same process as the conductive layer 104.

[0276] Note that the diameter of the opening 146 provided in the conductive layer 112b, the insulating layer 110, and the conductive layer 103 may be the same as or different from the diameter of the opening 146a provided in the conductive layer 112b, the insulating layer 110, and the conductive layer 103a. By changing the diameters of the two openings, two transistors with different channel widths can also be manufactured. Furthermore, the shape of the opening 146 and the shape of the opening 146a may be the same as or different from each other.

[0277] [Semiconductor device 10B] Fig. 10C shows a circuit diagram of the semiconductor device 10B. Fig. 14A shows a top view of the semiconductor device 10B. Fig. 14B is a cross-sectional view taken along dashed dotted line A1-A2 in Fig. 14A, and Fig. 14C is a cross-sectional view taken along dashed dotted line B1-B2 in Fig. 14A.

[0278] The semiconductor device 10B includes a transistor 100 and a transistor 200. One of the source and the drain of the transistor 200 is electrically connected to the one of the source and the drain of the transistor 100.

[0279] The transistor 100 and the transistor 200 are each provided over a substrate 102 .

[0280] The transistor 100 has the above-described structure, and therefore detailed description thereof will be omitted (see FIGS. 1 and 2).

[0281] The transistor 200 includes a conductive layer 112c, a conductive layer 103, a semiconductor layer 108a, a conductive layer 112a, an insulating layer 106, and a conductive layer 104a.

[0282] The conductive layer 112c functions as the other of the source electrode and the drain electrode of the transistor 200. The conductive layer 112c can be formed using the same material and in the same process as the conductive layer 112b.

[0283] The semiconductor layer 108a can be formed using the same material and in the same process as the semiconductor layer 108. Alternatively, the semiconductor layer 108 and the semiconductor layer 108a may be formed using different materials and in different processes.

[0284] The conductive layer 112a functions as one of a source electrode and a drain electrode of the transistor 100 and also functions as one of a source electrode and a drain electrode of the transistor 200. When the conductive layer 112a is shared between the transistors 100 and 200, the area occupied by the semiconductor device can be reduced.

[0285] The conductive layer 104a functions as a gate electrode of the transistor 200. The conductive layer 104a can be formed using the same material and in the same process as the conductive layer 104.

[0286] [Semiconductor Device 10C] Fig. 10D shows a circuit diagram of the semiconductor device 10C. Fig. 15A shows a top view of the semiconductor device 10C. Fig. 15B is a cross-sectional view taken along dashed line A1-A2 in Fig. 15A.

[0287] The semiconductor device 10C includes a transistor 100 and a transistor 250. One of the source and the drain of the transistor 250 is electrically connected to one of the source and the drain of the transistor 100.

[0288] 10D to 10H, the transistor 100 is illustrated as an n-channel transistor and the transistor 250 is illustrated as a p-channel transistor, but one embodiment of the present invention is not limited thereto. Both the transistor 100 and the transistor 250 may be n-channel transistors or p-channel transistors. Alternatively, the transistor 100 may be a p-channel transistor and the transistor 250 may be an n-channel transistor.

[0289] The transistor 100 and the transistor 250 are each provided over a substrate 102 .

[0290] The semiconductor device 10C has a conductive layer 259 on the substrate 102, an insulating layer 252 on the substrate 102 and the conductive layer 259, and a semiconductor layer 253 on the insulating layer 252. The semiconductor device 10C also has an insulating layer 254 on the insulating layer 252 and the semiconductor layer 253, and a conductive layer 255 on the insulating layer 254. The semiconductor layer 253 and the conductive layer 255 have overlapping regions.

[0291] An insulating layer 256 is provided over the insulating layer 254 and the conductive layer 255. An opening 257a is provided in the insulating layer 254 and the insulating layer 256 in a region overlapping with part of the semiconductor layer 253. An opening 257b is provided in the insulating layer 254 and the insulating layer 256 in a region overlapping with another part of the semiconductor layer 253.

[0292] A conductive layer 258a is provided over the insulating layer 256 and the opening 257a, and a conductive layer 258b is provided over the insulating layer 256 and the opening 257b. The conductive layer 258a is electrically connected to the semiconductor layer 253 in the opening 257a. The conductive layer 258b is electrically connected to the semiconductor layer 253 in the opening 257b. A conductive layer 103a in contact with the conductive layer 258a is provided over the conductive layer 258a, and a conductive layer 103b in contact with the conductive layer 258b is provided over the conductive layer 258b.

[0293] The semiconductor layer 253 has a drain region 253 a, a channel formation region 253 b, and a source region 253 c. In the semiconductor layer 253, a region overlapping with the conductive layer 255 functions as the channel formation region 253 b. The drain region 253 a is electrically connected to the conductive layer 258 a, and the source region 253 c is electrically connected to the conductive layer 258 b.

[0294] In addition, the insulating layer 110 (insulating layers 110a, 110b, and 110c) is provided over the insulating layer 256, the conductive layer 103a, and the conductive layer 103b, and the conductive layer 112b is provided over the insulating layer 110.

[0295] In addition, an opening 146 is provided in the conductive layer 112b, the insulating layer 110, and the conductive layer 103a in a region overlapping with part of the conductive layer 258a (FIG. 15A).

[0296] The insulating layer 106 is provided over the insulating layer 110, the conductive layer 112b, and the semiconductor layer 108, and the conductive layer 104 is provided over the insulating layer 106. The insulating layer 195 is provided over the insulating layer 106 and the conductive layer 104.

[0297] The conductive layer 259 functions as a backgate electrode of the transistor 250. Therefore, the conductive layer 259 preferably overlaps with the channel formation region 253b and extends beyond the edge of the channel formation region 253b. That is, the conductive layer 259 is preferably larger than the channel formation region 253b. Furthermore, the conductive layer 259 preferably extends beyond the edge of the semiconductor layer 253. That is, the conductive layer 259 is preferably larger than the semiconductor layer 253.

[0298] The back gate electrode is disposed so as to sandwich a channel formation region of the semiconductor layer between the gate electrode and the back gate electrode. The threshold voltage of the transistor can be changed by changing the potential of the back gate electrode. The potential of the back gate electrode may be ground potential or any other potential.

[0299] The back gate electrode is formed of a conductive layer and can function in the same manner as the gate electrode. For example, the potential of the back gate electrode may be set to the same potential as that of the gate electrode.

[0300] The back gate electrode can be formed using the same materials and methods as the gate electrode, source electrode, drain electrode, etc. Furthermore, since the gate electrode and the back gate electrode are conductive layers, they have a function of preventing an electric field generated outside the transistor from acting on the semiconductor layer in which the channel is formed (particularly, an electric field shielding function against static electricity). That is, the electrical characteristics of the transistor can be prevented from fluctuating due to the influence of an external electric field such as static electricity. Furthermore, by providing the back gate electrode, the amount of change in the threshold voltage of the transistor before and after a BT (Bias Temperature) stress test can be reduced. By providing the back gate electrode, the variation in the characteristics of the transistor can be reduced, and the reliability of the semiconductor device can be improved.

[0301] The semiconductor layer 253 functions as a semiconductor layer in which a channel of the transistor 250 is formed, the insulating layer 254 functions as a gate insulating layer, and the conductive layer 255 functions as a gate electrode. The conductive layer 258a functions as a drain electrode of the transistor 250, and the conductive layer 258b functions as a source electrode.

[0302] Like the transistor 100, the transistor 250 may be an OS transistor.

[0303] Here, the same material or different materials may be used for the semiconductor layer 108 and the semiconductor layer 253. For the configurations of the semiconductor layer 108 and the semiconductor layer 253, the description of the semiconductor layer 108 and the semiconductor layer 108a in the semiconductor device 10 can also be referred to.

[0304] Alternatively, the transistor 250 may be a transistor using silicon for a channel formation region (a Si transistor).

[0305] Examples of silicon include single crystal silicon, polycrystalline silicon, and amorphous silicon. In particular, a transistor having an LTPS semiconductor layer (hereinafter also referred to as an LTPS transistor) can be used. The LTPS transistor has high field-effect mobility and favorable frequency characteristics.

[0306] The transistor 100 has a structure similar to that described above except that the conductive layer 258a and the conductive layer 103a are included instead of the conductive layer 112a and the conductive layer 103 (see FIGS. 1 and 2).

[0307] The conductive layer 258a functions as one of a source electrode and a drain electrode of the transistor 100 and also functions as one of a source electrode and a drain electrode of the transistor 250. When the conductive layer 258a is shared by the transistors 100 and 250, the area occupied by the semiconductor device can be reduced.

[0308] As described above, the transistor 100 is a vertical channel transistor. On the other hand, in the transistor 250, the current flowing through the semiconductor layer flows in a horizontal direction, that is, in a direction parallel or substantially parallel to the surface of the substrate 102. Such a transistor can be called a horizontal channel transistor.

[0309] In this manner, the semiconductor device of one embodiment of the present invention may include not only a vertical channel transistor but also a lateral channel transistor.

[0310] As shown in Fig. 10E, the back gate and the gate of the transistor 250 may be electrically connected. Alternatively, as shown in Fig. 10F, the back gate and the source or the drain of the transistor 250 may be electrically connected. Alternatively, as shown in Fig. 10G, the transistor 250 does not need to have a back gate.

[0311] [Semiconductor Device 10D] Fig. 10H shows a circuit diagram of the semiconductor device 10D. Fig. 16A shows a top view of the semiconductor device 10D. Fig. 16B is a cross-sectional view taken along the dashed dotted line A1-A2 in Fig. 16A.

[0312] The semiconductor device 10D includes a transistor 100 and a transistor 250. A gate of the transistor 250 is electrically connected to one of the source and the drain of the transistor 100.

[0313] The semiconductor device 10D differs from the semiconductor device 10C in that the opening 146 overlaps with a conductive layer 255 that functions as a gate electrode of the transistor 250. Thus, in the semiconductor device 10C, the transistor 100 overlaps with the gate electrode of the transistor 250. In the semiconductor device 10D, the opening 146 is formed by selectively removing parts of the conductive layer 112b, the insulating layer 110, and the conductive layer 103 in a region overlapping with the conductive layer 255.

[0314] 16A and 16B, the opening 146 overlaps with the channel formation region 253b, but this is not limiting. The opening 146 may not overlap with the channel formation region 253b and may overlap with the conductive layer 255. In the semiconductor device 10D, the conductive layer 255 functions as the gate electrode of the transistor 250 and also as one of the source and drain electrodes of the transistor 100.

[0315] By providing the transistor 100 and the transistor 250 so as to overlap, a semiconductor device with a smaller occupation area can be realized.

[0316] Furthermore, the semiconductor device 10D differs from the semiconductor device 10C in the configurations of the opening 257a, the opening 257b, the conductive layer 258a, and the conductive layer 258b.

[0317] In the semiconductor device 10D, the opening 257a is formed by selectively removing a portion of each of the insulating layer 254 and the insulating layer 110 in a region overlapping with the drain region 253a of the semiconductor layer 253. In addition, in the semiconductor device 10D, the opening 257b is formed by selectively removing a portion of each of the insulating layer 254 and the insulating layer 110 in a region overlapping with the source region 253c of the semiconductor layer 253.

[0318] In the semiconductor device 10D, the conductive layer 258a and the conductive layer 258b are provided on the insulating layer 110.

[0319] In the semiconductor device 10D, the conductive layers 258a and 258b can be formed simultaneously using the same material and in the same manufacturing process as the conductive layer 112b. Since it is not necessary to separately manufacture the conductive layers 258a and 258b and the conductive layer 112b, the manufacturing process of the semiconductor device can be shortened, and the productivity of the semiconductor device can be improved.

[0320] A semiconductor device of one embodiment of the present invention includes at least one transistor and at least one capacitor, and has a structure in which a source or a drain of the transistor is electrically connected to one of a pair of electrodes of the capacitor. FIG. 10I illustrates an example in which the source or the drain of the transistor 100 is electrically connected to one of the electrodes of the capacitor 190.

[0321] The transistor of one embodiment of the present invention is a type of vertical transistor, and since a source electrode, a semiconductor layer, and a drain electrode can be provided in a stacked manner, the occupied area can be significantly reduced compared to a planar transistor. Furthermore, by using a p-channel Si transistor as the planar transistor and an n-channel OS transistor as the vertical transistor, a complementary metal oxide semiconductor (CMOS) circuit can be configured. Furthermore, by using this structure and providing the planar transistor and the vertical transistor in a stacked manner, the occupied area of ​​the CMOS circuit can be reduced.

[0322] In the transistor of one embodiment of the present invention, a good positional relationship between the gate electrode and the channel formation region in the semiconductor layer prevents a decrease in field-effect mobility, thereby enabling a reduction in driving voltage and power consumption of the semiconductor device.

[0323] In addition, the semiconductor layer in the transistor of one embodiment of the present invention includes a low-resistance region between a region in contact with the drain electrode and a channel formation region, which makes it difficult for a high electric field to be generated near the drain region, thereby suppressing generation of hot carriers and preventing deterioration of the transistor.

[0324] This embodiment mode can be combined with other embodiment modes as appropriate. In addition, in this specification, when a plurality of configuration examples are shown in one embodiment mode, the configuration examples can be combined as appropriate.

[0325] 17 to 19. Note that with regard to materials and formation methods of elements, descriptions of parts similar to those described in Embodiment 1 may be omitted.

[0326] 17 to 19 show a cross-sectional view taken along dashed dotted line A1-A2 in FIG. 1A and a cross-sectional view taken along dashed dotted line B1-B2 in FIG. 1A side by side.

[0327] Thin films (insulating films, semiconductor films, conductive films, etc.) constituting semiconductor devices can be formed using a sputtering method, a chemical vapor deposition (CVD) method, a vacuum evaporation method, a pulsed laser deposition (PLD) method, an ALD method, etc. CVD methods include a PECVD method and a thermal CVD method. One type of thermal CVD method is a metal organic chemical vapor deposition (MOCVD) method.

[0328] Furthermore, thin films (insulating films, semiconductor films, conductive films, etc.) constituting the semiconductor device can be formed by a wet film formation method such as spin coating, dipping, spray coating, inkjet, dispensing, screen printing, offset printing, doctor knife method, slit coating, roll coating, curtain coating, or knife coating.

[0329] Furthermore, when processing a thin film that constitutes a semiconductor device, a photolithography method or the like can be used. Alternatively, the thin film may be processed by a nanoimprint method, a sandblasting method, a lift-off method, or the like. Furthermore, an island-shaped thin film may be directly formed by a film formation method using a shielding mask such as a metal mask.

[0330] There are two typical photolithography methods: one is to form a resist mask on the thin film to be processed, process the thin film by etching or the like, and then remove the resist mask; the other is to form a photosensitive thin film, and then process the thin film into the desired shape by exposure and development.

[0331] In photolithography, the light used for exposure may be, for example, i-line (wavelength 365 nm), g-line (wavelength 436 nm), h-line (wavelength 405 nm), or a mixture of these. Other light sources that can be used include ultraviolet light, KrF laser light, ArF laser light, etc. Exposure may also be performed by immersion exposure technology. Extreme ultraviolet (EUV) light or X-rays may also be used as the light used for exposure. An electron beam may also be used instead of the light used for exposure. Extreme ultraviolet light, X-rays, or an electron beam are preferred because they enable extremely fine processing. When exposure is performed by scanning a beam such as an electron beam, a photomask is not required.

[0332] For etching the thin film, dry etching, wet etching, sandblasting, or the like can be used.

[0333] First, a conductive layer 112a is formed on a substrate 102, and a conductive layer 103f is formed on the conductive layer 112a (FIG. 17A).

[0334] The conductive film that will become the conductive layer 112a and the conductive film that will become the conductive layer 103f are preferably formed by, for example, sputtering. A resist mask can be formed on the conductive film by a photolithography process, and then the conductive film can be processed to form the conductive layer. The conductive film that will become the conductive layer 103f may be formed after the conductive layer 112a is formed. Alternatively, the conductive film that will become the conductive layer 103f may be formed and processed into the conductive layer 103f, and then the conductive film that will become the conductive layer 112a may be processed to form the conductive layer 112a. Note that the conductive layer 103 having the opening 148 can also be formed at this stage, but it is preferable to process the conductive film that will become the conductive layer 103f only into a desired shape, such as an island shape. Then, after opening the insulating layer 110, the conductive layer 103f is preferably opened and the conductive layer 103 is formed. This makes it easier to align the shapes of the openings in the insulating layer 110 and the conductive layer 103. The conductive film can be processed by using either or both of a wet etching method and a dry etching method.

[0335] Subsequently, an insulating film 110af that will become the insulating layer 110a and an insulating film 110bf that will become the insulating layer 110b are formed on the conductive layer 103f (FIG. 17B).

[0336] For example, the insulating film 110af is preferably a silicon nitride film or an aluminum oxide film, and the insulating film 110bf is preferably a silicon oxide film or a silicon oxynitride film.

[0337] The insulating films 110af and 110bf are preferably formed by, for example, sputtering or PECVD. After forming the insulating film 110af, it is preferable to form the insulating film 110bf in succession in vacuum without exposing the surface of the insulating film 110af to the atmosphere. By successively forming the insulating films 110af and 110bf, it is possible to prevent impurities from the atmosphere from adhering to the surface of the insulating film 110af. Examples of such impurities include water and organic substances.

[0338] The substrate temperature during the formation of the insulating films 110af and 110bf is preferably 180° C. or higher and 450° C. or lower, more preferably 200° C. or higher and 450° C. or lower, further preferably 250° C. or higher and 450° C. or lower, further preferably 300° C. or higher and 450° C. or lower, further preferably 300° C. or higher and 400° C. or lower, further preferably 350° C. or higher and 400° C. or lower. By setting the substrate temperature during the formation of the insulating films 110af and 110bf within the above-described range, it is possible to reduce the release of impurities (e.g., water and hydrogen) from the insulating films themselves and to suppress the diffusion of impurities into the semiconductor layer 108. Therefore, a transistor exhibiting good electrical characteristics and high reliability can be obtained.

[0339] Since the insulating films 110af and 110bf are formed before the semiconductor layer 108, there is no need to worry about oxygen being desorbed from the semiconductor layer 108 due to heat applied during the formation of the insulating films 110af and 110bf.

[0340] After forming the insulating film 110bf, it is preferable to perform plasma treatment in an atmosphere containing oxygen without exposing the insulating film 110bf to the air (in-situ). ２O plasma treatment is preferably performed. By performing such plasma treatment, oxygen can be supplied to the insulating film 110bf.

[0341] After the insulating films 110af and 110bf are formed, heat treatment may be performed. By performing the heat treatment, water and hydrogen can be released from the surfaces and the interiors of the insulating films 110af and 110bf.

[0342] The temperature of the heat treatment is preferably 150° C. or higher and lower than the strain point of the substrate, more preferably 200° C. or higher and 450° C. or lower, further preferably 250° C. or higher and 450° C. or lower, further preferably 300° C. or higher and 450° C. or lower, further preferably 300° C. or higher and 400° C. or lower, and further preferably 350° C. or higher and 400° C. or lower. The heat treatment can be performed in an atmosphere containing one or more of a noble gas, nitrogen, or oxygen. As the nitrogen-containing atmosphere or the oxygen-containing atmosphere, dry air (CDA: Clean Dry Air) may be used. Note that the content of hydrogen, water, and the like in the atmosphere is preferably as low as possible. As the atmosphere, it is preferable to use a high-purity gas with a dew point of −60° C. or lower, preferably −100° C. or lower. Using an atmosphere containing as little hydrogen, water, and the like as possible can prevent hydrogen, water, and the like from being taken into the insulating film 110af and the insulating film 110bf as much as possible. The heat treatment can be performed using an oven, a rapid thermal annealing (RTA) device, etc. By using an RTA device, the heat treatment time can be shortened.

[0343] Subsequently, a metal oxide layer 149 is preferably formed on the insulating film 110bf (FIG. 17C). By forming the metal oxide layer 149, oxygen can be supplied to the insulating film 110bf.

[0344] The conductivity of the metal oxide layer 149 does not matter. At least one of an insulating film, a semiconductor film, and a conductive film can be used as the metal oxide layer 149. For example, aluminum oxide, hafnium oxide, hafnium aluminate, indium oxide, indium tin oxide (ITO), or indium tin oxide containing silicon (ITSO) can be used as the metal oxide layer 149.

[0345] The metal oxide layer 149 is preferably formed using an oxide material containing one or more of the same elements as those of the semiconductor layer 108. In particular, it is preferable to use an oxide semiconductor material that can be used for the semiconductor layer 108. For example, it is preferable to use IGZO for both the metal oxide layer 149 and the semiconductor layer 108.

[0346] When forming the metal oxide layer 149, the amount of oxygen supplied to the insulating film 110bf can be increased by increasing the ratio of the oxygen flow rate to the total flow rate of the film formation gas introduced into the treatment chamber of the film formation apparatus (oxygen flow rate ratio) or the oxygen partial pressure in the treatment chamber. The oxygen flow rate ratio or the oxygen partial pressure is, for example, 50% to 100%, preferably 65% ​​to 100%, more preferably 80% to 100%, and even more preferably 90% to 100%. In particular, it is preferable to set the oxygen flow rate ratio to 100% and the oxygen partial pressure as close to 100% as possible.

[0347] By forming the metal oxide layer 149 by sputtering in an oxygen-containing atmosphere in this manner, oxygen can be supplied to the insulating film 110bf and oxygen can be prevented from being released from the insulating film 110bf during the formation of the metal oxide layer 149. As a result, a large amount of oxygen can be trapped in the insulating film 110bf. Then, a large amount of oxygen can be supplied to the semiconductor layer 108 by subsequent heat treatment. As a result, oxygen vacancies and V in the semiconductor layer 108 can be reduced. Ｏ H can be reduced, and a highly reliable transistor can be obtained that exhibits favorable electrical characteristics.

[0348] It is preferable to perform heat treatment after forming the metal oxide layer 149. The above description can be referred to for the heat treatment, and therefore detailed description thereof will be omitted. By performing heat treatment after forming the metal oxide layer 149, oxygen can be effectively supplied from the metal oxide layer 149 to the insulating film 110bf.

[0349] After the metal oxide layer 149 is formed or after the heat treatment, oxygen may be supplied to the insulating film 110bf through the metal oxide layer 149. Oxygen can be supplied by, for example, ion implantation, ion doping, plasma immersion ion implantation, or plasma treatment. In the plasma treatment in the method for manufacturing a semiconductor device of one embodiment of the present invention, an apparatus that converts oxygen gas into plasma by high-frequency power can be preferably used. Examples of the apparatus that converts gas into plasma by high-frequency power include a plasma etching apparatus and a plasma ashing apparatus.

[0350] Subsequently, the metal oxide layer 149 is removed.

[0351] Although there is no particular limitation on the method for removing the metal oxide layer 149, a wet etching method can be suitably used. By using the wet etching method, etching of the insulating film 110bf can be suppressed when removing the metal oxide layer 149. This can suppress the thickness of the insulating film 110bf from becoming thin, and can make the thickness of the insulating layer 110b uniform.

[0352] The process of supplying oxygen to the insulating film 110bf is not limited to the above-described method. For example, oxygen radicals, oxygen atoms, oxygen atomic ions, oxygen molecular ions, or the like can be supplied to the insulating film 110bf by ion doping, ion implantation, or plasma treatment. Alternatively, a film that suppresses oxygen desorption may be formed on the insulating film 110bf, and then oxygen may be supplied to the insulating film 110bf through the film. The film is preferably removed after supplying oxygen. The film that suppresses oxygen desorption may be a conductive film or a semiconductor film containing one or more of indium, zinc, gallium, tin, aluminum, chromium, tantalum, titanium, molybdenum, nickel, iron, cobalt, and tungsten.

[0353] Next, an insulating film 110cf, which will become the insulating layer 110c, is formed on the insulating film 110bf (FIG. 17D). The description of the formation of the insulating film 110cf can be referenced, so a detailed description thereof will be omitted. The conditions for forming the insulating film 110af and the insulating film 110cf may be the same or different.

[0354] When the transistor 100B illustrated in FIGS. 5A to 5C is manufactured, an insulating film to be the insulating layer 110d is further formed over the insulating film 110cf.

[0355] For example, it is preferable to form a silicon nitride film or an aluminum oxide film as the insulating film 110cf. Also, it is preferable to form a silicon nitride film as the insulating film 110df (not shown) that becomes the insulating layer 110d.

[0356] As described above, the insulating layer 110d has a region with a higher hydrogen content than the insulating layer 110c.

[0357] The deposition gas for the insulating film 110df is higher in NH than the deposition gas for the insulating film 110cf. ３ The gas flow rate of the insulating film 110cf is preferably high. ３ NH3 gas may not be used. ３ By forming the insulating film 110df under conditions where the gas flow rate is high, the hydrogen content in the insulating film 110df can be increased. This can increase the amount of hydrogen released by heating the insulating layer 110d. Also, the amount of hydrogen released by heating the insulating layer 110c can be reduced.

[0358] Furthermore, by differentiating the deposition conditions for the insulating films 110cf and 110df, the amount of hydrogen released by heating in the insulating layer 110d can be adjusted. Specifically, the deposition conditions for the insulating films 110cf and 110df can be varied by varying one or more of the deposition power (deposition power density), deposition pressure, deposition gas type, deposition gas flow rate ratio, deposition temperature, and distance between the substrate and the electrode. For example, by making the deposition power density of the insulating film 110df lower than that of the insulating film 110cf, the hydrogen content in the insulating film 110df can be made higher than that in the insulating film 110cf. This allows the amount of hydrogen released by heating in the insulating layer 110d to be increased.

[0359] The insulating films 110cf and 110df are preferably formed by, for example, a sputtering method or a PECVD method. In particular, the PECVD method is preferable because it allows easy formation of both a film with a low hydrogen content and a film with a high hydrogen content.

[0360] After the insulating film 110cf is formed, it is preferable to form the insulating film 110df successively in a vacuum without exposing the surface of the insulating film 110cf to the atmosphere. By successively forming the insulating films 110cf and 110df, it is possible to prevent impurities from the atmosphere from adhering to the surface of the insulating film 110cf.

[0361] The substrate temperature during the formation of the insulating films 110cf and 110df is preferably 180° C. or higher and 450° C. or lower, more preferably 200° C. or higher and 450° C. or lower, even more preferably 250° C. or higher and 450° C. or lower, even more preferably 300° C. or higher and 450° C. or lower, even more preferably 300° C. or higher and 400° C. or lower, and even more preferably 350° C. or higher and 400° C. or lower. By setting the substrate temperature during the formation of the insulating films 110cf and 110df within the above-mentioned range, it is possible to reduce the release of impurities (e.g., water and hydrogen) from the insulating films themselves and to suppress the diffusion of impurities into the semiconductor layer 108. Therefore, a transistor exhibiting good electrical characteristics and high reliability can be obtained.

[0362] Next, a conductive film 112f that will become the conductive layer 112b is formed on the insulating film 110cf (FIG. 18A). The conductive film 112f is preferably formed by, for example, sputtering.

[0363] Next, a conductive layer 112b having an opening 143 is formed. In this embodiment, an example is shown in which the conductive film 112f is processed into the conductive layer 112B having a desired shape, such as an island shape, as shown in FIG. 18B , and then the opening 143 is provided in the conductive layer 112B as shown in FIG. 18C , thereby forming the conductive layer 112b. As a result, the openings 141 and 148 can be formed using the resist mask used to form the opening 143. Furthermore, the steps of forming the openings 141 and 148 can be performed consecutively with the step of forming the opening 143. This makes it easier to align the shapes of the openings in the conductive layer 112b, the insulating layer 110, and the conductive layer 103. On the other hand, the conductive layer 112b may be formed by providing the opening 143 in the conductive film 112f and then processing it into a desired shape.

[0364] The conductive film 112f can be processed (which can also be referred to as forming the conductive layer 112B and the conductive layer 112b) by wet etching or dry etching, or both. In particular, the wet etching is suitable for forming the opening 143.

[0365] Next, openings 141 are formed in the insulating films 110af, 110bf, and 110cf, and an opening 148 is formed in the conductive layer 103f, thereby forming the conductive layer 103 and the insulating layer 110 (insulating layers 110a, 110b, and 110c) ( FIG. 18C ). The openings 141 and 148 are provided at positions overlapping with the opening 143 in the conductive layer 112b. By providing the openings 141 and 148, regions of the conductive layer 112a that overlap with the openings 141, 143, and 148 are exposed.

[0366] One or both of a wet etching method and a dry etching method can be used to form the openings 141 and 148. For example, it is preferable to form both the openings 141 and 148 by a dry etching method because the surfaces of the conductive layer 103 and the insulating layer 110 in the openings can be aligned (the difference in level can be reduced).

[0367] As described above, the openings 141 and 148 can be formed using, for example, the resist mask used to form the opening 143. Specifically, a resist mask is formed over the conductive layer 112B, a part of the conductive layer 112B is removed using the resist mask to form the opening 143, parts of the insulating films 110af, 110bf, and 110cf are removed using the resist mask to form the opening 141, and further a part of the conductive layer 103f is removed to form the opening 148. Note that one or both of the openings 141 and 148 may be formed using a resist mask different from the resist mask used to form the opening 143.

[0368] Next, a metal oxide film 108f to be the semiconductor layer 108 is formed so as to cover the openings 141, 143, and 148 (FIG. 19A). The metal oxide film 108f is provided in contact with the top and side surfaces of the conductive layer 112b, the top and side surfaces of the insulating layer 110, the side surfaces of the conductive layer 103, and the top surface of the conductive layer 112a.

[0369] Note that the side surface of the conductive layer 103 at the opening 148 may be oxidized due to contact with the metal oxide film 108f. Depending on the material of the conductive layer 103, the conductivity of the conductive layer 103 may be reduced due to oxidation. Since the conductive layer 103 and the metal oxide film 108f do not need to be electrically connected, the side surface of the conductive layer 103 at the opening 148 may be oxidized. For example, an oxide of the conductive layer 103 may exist between the conductive layer 103 and the metal oxide film 108f.

[0370] The metal oxide film 108f is preferably formed as a film with as uniform a thickness as possible on the side surface of the opening 148 in the conductive layer 103, the side surface of the opening 141 in the insulating layer 110, and the side surface of the opening 143 in the conductive layer 112b. The metal oxide film 108f can be formed by, for example, a sputtering method or an ALD method.

[0371] The metal oxide film 108f is preferably formed by a sputtering method using a metal oxide target.

[0372] The metal oxide film 108f is preferably a dense film with as few defects as possible. Furthermore, the metal oxide film 108f is preferably a high-purity film in which impurities including hydrogen are reduced as much as possible. In particular, it is preferable to use a crystalline metal oxide film as the metal oxide film 108f.

[0373] When the metal oxide film 108f is formed, oxygen gas is preferably used. By using oxygen gas when the metal oxide film 108f is formed, oxygen can be suitably supplied into the insulating layer 110. For example, when an oxide is used for the insulating layer 110b, oxygen can be suitably supplied into the insulating layer 110b.

[0374] By supplying oxygen to the insulating layer 110b, oxygen is supplied to the semiconductor layer 108 in a later step, and oxygen vacancies and V Ｏ H can be reduced.

[0375] When forming the metal oxide film 108f, oxygen gas may be mixed with an inert gas (e.g., helium gas, argon gas, xenon gas, etc.). Note that the higher the ratio of oxygen gas to the total deposition gas when forming the metal oxide film 108f (oxygen flow ratio), the higher the crystallinity of the metal oxide film 108f, resulting in a highly reliable transistor. On the other hand, the lower the oxygen flow ratio, the lower the crystallinity of the metal oxide film 108f, resulting in a transistor with a large on-state current.

[0376] The higher the substrate temperature when the metal oxide film 108f is formed, the higher the crystallinity and density of the metal oxide film 108f.On the other hand, the lower the substrate temperature, the lower the crystallinity and electrical conductivity of the metal oxide film 108f.

[0377] The substrate temperature during the formation of the metal oxide film 108f is preferably from room temperature to 250° C., more preferably from room temperature to 200° C., and even more preferably from room temperature to 140° C. For example, a substrate temperature of from room temperature to 140° C. is preferable because productivity is increased. Furthermore, by forming the metal oxide film 108f at room temperature or without heating the substrate, the crystallinity can be reduced.

[0378] When the ALD method is used, it is preferable to use a film formation method such as a thermal ALD method or PEALD (Plasma Enhanced ALD). The thermal ALD method is preferable because it exhibits extremely high step coverage. The PEALD method is preferable because it exhibits high step coverage and allows low-temperature film formation.

[0379] The metal oxide film 108f can be formed by, for example, an ALD method using a precursor containing a constituent metal element and an oxidizing agent.

[0380] For example, when forming an In—Ga—Zn oxide film, three precursors, i.e., a precursor containing indium, a precursor containing gallium, and a precursor containing zinc, can be used, or two precursors, i.e., a precursor containing indium and a precursor containing gallium and zinc, can be used.

[0381] Examples of precursors containing indium include triethylindium, tris(2,2,6,6-tetramethyl-3,5-heptanedionate)indium, cyclopentadienylindium, indium(III) chloride, and (3-(dimethylamino)propyl)dimethylindium.

[0382] Gallium-containing precursors include, for example, trimethylgallium, triethylgallium, tris(dimethylamido)gallium(III), gallium(III) acetylacetonate, tris(2,2,6,6-tetramethyl-3,5-heptanedionate)gallium, dimethylchlorogallium, diethylchlorogallium, and gallium(III) chloride.

[0383] Examples of zinc-containing precursors include dimethylzinc, diethylzinc, zinc bis(2,2,6,6-tetramethyl-3,5-heptanedionate), and zinc chloride.

[0384] Oxidizing agents include, for example, ozone, oxygen, and water.

[0385] Methods for controlling the composition of the resulting film include adjusting the flow rate ratio of the source gases, the time for which the source gases are flowed, the order in which the source gases are flowed, etc. By adjusting these, it is also possible to form a film whose composition changes continuously. It is also possible to form films with different compositions successively.

[0386] Before forming the metal oxide film 108f, it is preferable to perform at least one of a treatment for removing water, hydrogen, organic substances, and the like adsorbed on the surface of the insulating layer 110 and a treatment for supplying oxygen into the insulating layer 110. For example, heat treatment can be performed at a temperature of 70° C. or higher and 200° C. or lower in a reduced pressure atmosphere. Alternatively, plasma treatment in an atmosphere containing oxygen may be performed. Alternatively, dinitrogen monoxide (N ２ Oxygen may be supplied to the insulating layer 110 by plasma treatment in an atmosphere containing an oxidizing gas such as nitrous oxide (NO). When plasma treatment containing nitrous oxide gas is performed, oxygen can be supplied while organic substances on the surface of the insulating layer 110 are suitably removed. After such treatment, it is preferable to form the metal oxide film 108f continuously without exposing the surface of the insulating layer 110 to the air.

[0387] In addition, when the semiconductor layer 108 has a stacked structure, it is preferable to form a metal oxide film first, and then form a next metal oxide film in succession without exposing the surface of the first metal oxide film to the air.

[0388] When the semiconductor layer 108 has a stacked structure, all layers constituting the semiconductor layer 108 may be formed by the same film formation method (for example, sputtering or ALD), or different film formation methods may be used for each layer. For example, the first metal oxide layer may be formed by sputtering, and the second metal oxide layer may be formed by ALD.

[0389] Subsequently, the metal oxide film 108f is processed into an island shape to form the semiconductor layer 108 (FIG. 19B).

[0390] The semiconductor layer 108 can be formed by using one or both of a wet etching method and a dry etching method. For example, a wet etching method is preferable. At this time, a part of the conductive layer 112b in a region that does not overlap with the semiconductor layer 108 may be etched and thinned. Similarly, a part of the insulating layer 110 in a region that does not overlap with both the semiconductor layer 108 and the conductive layer 112b may be etched and thinned. For example, the insulating layer 110c of the insulating layer 110 may be removed by etching, exposing the surface of the insulating layer 110b. Note that, in etching the metal oxide film 108f, using a material with a high selectivity for the insulating layer 110c can prevent the insulating layer 110c from becoming thin.

[0391] Heat treatment is preferably performed after the metal oxide film 108f is formed or after the metal oxide film 108f is processed into the semiconductor layer 108. The heat treatment can remove hydrogen or water contained in or adsorbed on the surface of the metal oxide film 108f or the semiconductor layer 108. The heat treatment may improve the film quality of the metal oxide film 108f or the semiconductor layer 108 (for example, reduce defects or improve crystallinity). The heat treatment is more preferably performed before processing into the semiconductor layer 108.

[0392] By heat treatment, oxygen is preferably supplied from the insulating layer 110b to at least a part of the metal oxide film 108f or at least a part of the semiconductor layer 108. A region of the semiconductor layer 108 that is in contact with the insulating layer 110b and its vicinity functions as a channel formation region. By supplying oxygen to this region, oxygen vacancies in the channel formation region can be reduced, and the carrier concentration can be lowered. That is, the channel formation region can be made into an i-type (intrinsic) or substantially i-type region. This allows the transistor to have stable electrical characteristics.

[0393] Note that during this heat treatment or other heat treatments in the process, oxygen contained in the semiconductor layer 108 may be extracted by the conductive layer 103, forming oxygen vacancies in the semiconductor layer 108. When impurities such as hydrogen enter the oxygen vacancies, the impurities function as donors, and the carrier concentration tends to increase. Therefore, the region of the semiconductor layer 108 that is in contact with the conductive layer 103 and its vicinity can be made into a low-resistance region.

[0394] Alternatively, hydrogen may be supplied from the conductive layer 103 to part of the metal oxide film 108f or the semiconductor layer 108. This is preferable because it facilitates reducing the resistance of a region of the semiconductor layer 108 that is in contact with the conductive layer 103 and its vicinity. For example, hydrogen is supplied from the conductive layer 103 to a portion where the conductive layer 103 is in contact with the metal oxide film 108f or the semiconductor layer 108. Furthermore, during heat treatment in the process, the supply of hydrogen from the conductive layer 103 to the metal oxide film 108f or the semiconductor layer 108 may be promoted.

[0395] As for the heat treatment, the above description can be referred to, and therefore a detailed description thereof will be omitted.

[0396] Note that this heat treatment does not have to be performed if it is not necessary. Alternatively, the heat treatment may be omitted here and may be combined with a heat treatment performed in a later step. Furthermore, a high-temperature treatment in a later step (e.g., a film formation step) may also serve as this heat treatment.

[0397] Subsequently, the insulating layer 106 is formed to cover the semiconductor layer 108, the conductive layer 112b, and the insulating layer 110 (FIG. 19C). The insulating layer 106 is preferably formed by, for example, PECVD or ALD.

[0398] When an oxide semiconductor is used for the semiconductor layer 108, the insulating layer 106 preferably functions as a barrier film that suppresses oxygen diffusion. The insulating layer 106 has a function of suppressing oxygen diffusion, which suppresses oxygen from diffusing from above the insulating layer 106 to the conductive layer 104, thereby suppressing oxidation of the conductive layer 104. As a result, a highly reliable transistor can be obtained that exhibits favorable electrical characteristics.

[0399] In this specification and the like, a barrier film refers to a film having barrier properties. For example, an insulating layer having barrier properties can be referred to as a barrier insulating layer. In this specification and the like, the barrier properties refer to one or both of a function of suppressing the diffusion of a corresponding substance (also referred to as low permeability) and a function of capturing or fixing a corresponding substance (also referred to as gettering).

[0400] By increasing the temperature during the formation of the insulating layer 106 that functions as a gate insulating layer, the insulating layer can have fewer defects. However, if the temperature during the formation of the insulating layer 106 is high, oxygen is released from the semiconductor layer 108, causing oxygen vacancies and V in the semiconductor layer 108. Ｏ H may increase. The substrate temperature during the formation of the insulating layer 106 is preferably 180° C. or higher and 450° C. or lower, more preferably 200° C. or higher and 450° C. or lower, further preferably 250° C. or higher and 450° C. or lower, further preferably 300° C. or higher and 450° C. or lower, and further preferably 300° C. or higher and 400° C. or lower. By setting the substrate temperature during the formation of the insulating layer 106 within the above range, defects in the insulating layer 106 can be reduced and oxygen can be prevented from being released from the semiconductor layer 108. Therefore, a transistor exhibiting good electrical characteristics and high reliability can be obtained.

[0401] Before forming the insulating layer 106, plasma treatment may be performed on the surface of the semiconductor layer 108. The plasma treatment can reduce impurities such as water adsorbed on the surface of the semiconductor layer 108. Therefore, impurities at the interface between the semiconductor layer 108 and the insulating layer 106 can be reduced, and a highly reliable transistor can be realized. This is particularly suitable for the case where the surface of the semiconductor layer 108 is exposed to the air between the formation of the semiconductor layer 108 and the formation of the insulating layer 106. The plasma treatment can be performed in an atmosphere of oxygen, ozone, nitrogen, nitrous oxide, argon, or the like, for example. Furthermore, the plasma treatment and the formation of the insulating layer 106 are preferably performed successively without exposure to the air.

[0402] Furthermore, it is preferable to use a film containing a large amount of oxygen for the insulating layer 106, because oxygen can be supplied from the insulating layer 106 to the semiconductor layer 108. It is more preferable to use a film that releases oxygen when heated for the insulating layer 106. The insulating layer 106 releases oxygen due to heat applied during the manufacturing process of the transistor, so that oxygen can be supplied to the semiconductor layer 108. By supplying oxygen from the insulating layer 106 to the semiconductor layer 108, particularly to the channel formation region of the semiconductor layer 108, oxygen vacancies in the semiconductor layer 108 can be reduced, and a transistor with good electrical characteristics and high reliability can be obtained.

[0403] Next, a conductive layer 104 is formed over the insulating layer 106 ( FIG. 19C ). A sputtering method, a thermal CVD method (including an MOCVD method), or an ALD method is suitable for forming the conductive film that becomes the conductive layer 104. After a resist mask is formed on the conductive film by a photolithography process, the conductive film is processed to form an island-shaped conductive layer 104 that functions as a gate electrode.

[0404] Through the above steps, a semiconductor device of one embodiment of the present invention can be manufactured.

[0405] This embodiment mode can be combined with other embodiment modes as appropriate.

[0406] Embodiment 3 In this embodiment, a display device of one embodiment of the present invention will be described with reference to FIGS.

[0407] The display device of this embodiment can be a high-resolution display device or a large-sized display device. Therefore, the display device of this embodiment can be used in electronic devices having relatively large screens, such as television devices, desktop or notebook personal computers, computer monitors, digital signage, and large game machines such as pachinko machines, as well as in display units of digital cameras, digital video cameras, digital photo frames, mobile phones, portable game machines, personal digital assistants, and sound reproduction devices.

[0408] The display device of the present embodiment can be a high-definition display device, and can therefore be used as a display unit for information terminals (wearable devices) such as wristwatches and bracelets, as well as for wearable devices that can be worn on the head, such as VR devices such as head-mounted displays (HMDs) and AR devices such as glasses.

[0409] The semiconductor device of one embodiment of the present invention can be used for a display device or a module including the display device. Examples of the module including the display device include a module in which a connector such as a flexible printed circuit (hereinafter referred to as FPC) or a tape carrier package (TCP) is attached to the display device, and a module in which an integrated circuit (IC) is mounted by a chip-on-glass (COG) method, a chip-on-film (COF) method, or the like.

[0410] The display device of this embodiment may also have a function as a touch panel. For example, various detection elements (also referred to as sensor elements) that can detect the proximity or contact of a detection target such as a finger can be applied to the display device.

[0411] Examples of sensor types include a capacitance type, a resistive film type, a surface acoustic wave type, an infrared type, an optical type, and a pressure-sensitive type.

[0412] The capacitance type includes, for example, a surface capacitance type and a projected capacitance type. The projected capacitance type includes, for example, a self-capacitance type and a mutual capacitance type. The mutual capacitance type is preferred because it enables simultaneous multi-point detection.

[0413] Examples of touch panels include out-cell, on-cell, and in-cell types. Note that an in-cell touch panel is a type in which electrodes constituting a detection element are provided on one or both of a substrate supporting a display element and an opposing substrate.

[0414] [Display Device 50A] FIG. 20 shows a perspective view of the display device 50A.

[0415] The display device 50A has a configuration in which a substrate 152 and a substrate 151 are bonded together. In Fig. 20, the substrate 152 is indicated by a dashed line.

[0416] The display device 50A includes a display portion 162, a connection portion 140, a circuit portion 164, a conductive layer 165, etc. Fig. 20 shows an example in which an IC 173 and an FPC 172 are mounted on the display device 50A. Therefore, the configuration shown in Fig. 20 can also be said to be a display module including the display device 50A, an IC, and an FPC.

[0417] The connection portion 140 is provided on the outside of the display portion 162. The connection portion 140 can be provided along one side or multiple sides of the display portion 162. There may be one or multiple connection portions 140. FIG. 20 shows an example in which the connection portion 140 is provided so as to surround the four sides of the display portion. The connection portion 140 electrically connects the common electrode of the display element and the conductive layer, and can supply a potential to the common electrode.

[0418] The circuit portion 164 includes, for example, a scan line driver circuit (also referred to as a gate driver). Alternatively, the circuit portion 164 may include both a scan line driver circuit and a signal line driver circuit (also referred to as a source driver).

[0419] The conductive layer 165 has a function of supplying signals and power to the display portion 162 and the circuit portion 164. The signals and power are input to the conductive layer 165 from the outside through the FPC 172 or are input to the conductive layer 165 from the IC 173.

[0420] 20 shows an example in which an IC 173 is provided on a substrate 151 by a COG method, a COF method, or the like. The IC 173 may be, for example, an IC having one or both of a scanning line driver circuit and a signal line driver circuit. The display device 50A and the display module may be configured without an IC. The IC may also be mounted on an FPC by a COF method, or the like.

[0421] The semiconductor device of one embodiment of the present invention can be used for, for example, one or both of the display portion 162 and the circuit portion 164 of the display device 50A.

[0422] For example, when the semiconductor device of one embodiment of the present invention is applied to a pixel circuit of a display device, the area occupied by the pixel circuit can be reduced, resulting in a high-resolution display device. Furthermore, when the semiconductor device of one embodiment of the present invention is applied to a driver circuit of a display device (e.g., one or both of a gate line driver circuit and a source line driver circuit), the area occupied by the driver circuit can be reduced, resulting in a display device with a narrow frame. Furthermore, since the semiconductor device of one embodiment of the present invention has good electrical characteristics, its use in a display device can improve the reliability of the display device.

[0423] The display section 162 is an area in the display device 50A that displays an image, and has a plurality of periodically arranged pixels 201. Fig. 20 shows an enlarged view of one pixel 201.

[0424] The pixel arrangement in the display device of this embodiment is not particularly limited, and various methods can be applied, such as a stripe arrangement, an S-stripe arrangement, a matrix arrangement, a delta arrangement, a Bayer arrangement, and a pentile arrangement.

[0425] A pixel 201 shown in FIG. 20 has a sub-pixel 11R that emits red light, a sub-pixel 11G that emits green light, and a sub-pixel 11B that emits blue light.

[0426] Each of the sub-pixels 11R, 11G, and 11B includes a display element and a circuit that controls the driving of the display element.

[0427] Various elements can be used as the display element, including, for example, a liquid crystal element and a light-emitting element. Other examples include shutter-type or optical interference-type MEMS (Micro Electro Mechanical Systems) elements, display elements that employ a microcapsule method, an electrophoresis method, an electrowetting method, or an electronic liquid powder (registered trademark) method, etc. Furthermore, a QLED (Quantum-dot LED) that uses a light source and color conversion technology using quantum dot materials may also be used.

[0428] Examples of display devices using liquid crystal elements include transmissive liquid crystal display devices, reflective liquid crystal display devices, and semi-transmissive liquid crystal display devices.

[0429] Modes that can be used in display devices using liquid crystal elements include, for example, vertical alignment (VA) mode, fringe field switching (FFS) mode, in-plane switching (IPS) mode, twisted nematic (TN) mode, axially symmetric aligned micro-cell (ASM) mode, optically compensated birefringence (OCB) mode, ferroelectric liquid crystal (FLC) mode, antiferroelectric liquid crystal (AFLC) mode, and electrically compensated birefringence (ECB) mode. Examples of the VA mode include a Multi-Domain Vertical Alignment (MVA) mode, a Patterned Vertical Alignment (PVA) mode, and an Advanced Super View (ASV) mode.

[0430] Examples of liquid crystal materials that can be used in liquid crystal elements include thermotropic liquid crystals, low-molecular-weight liquid crystals, polymer liquid crystals, polymer-dispersed liquid crystals (PDLCs), polymer network liquid crystals (PNLCs), ferroelectric liquid crystals, and antiferroelectric liquid crystals. These liquid crystal materials exhibit cholesteric phases, smectic phases, cubic phases, chiral nematic phases, isotropic phases, blue phases, and the like, depending on the conditions. Furthermore, either positive-type or negative-type liquid crystals may be used as the liquid crystal material, and the type can be selected depending on the mode or design to be applied.

[0431] Examples of the light-emitting element include self-luminous light-emitting elements such as LEDs (Light Emitting Diodes), OLEDs (Organic LEDs), semiconductor lasers, etc. Examples of the LED that can be used include mini LEDs and micro LEDs.

[0432] Examples of light-emitting substances that the light-emitting element has include fluorescent substances (fluorescent materials), phosphorescent substances (phosphorescent materials), substances that exhibit thermally activated delayed fluorescence (thermally activated delayed fluorescence: TADF materials), and inorganic compounds (quantum dot materials, etc.).

[0433] The light-emitting element can emit light of infrared, red, green, blue, cyan, magenta, yellow, white, etc. Furthermore, the color purity can be improved by providing the light-emitting element with a microcavity structure.

[0434] One of a pair of electrodes included in the light-emitting element functions as an anode, and the other electrode functions as a cathode.

[0435] Note that the display device of one embodiment of the present invention may be any of a top-emission type that emits light in a direction opposite to a substrate on which a light-emitting element is formed, a bottom-emission type that emits light toward a substrate on which a light-emitting element is formed, and a dual-emission type that emits light to both sides.

[0436] Figure 21A shows an example of a cross section of the display device 50A when a portion of the area including the FPC 172, a portion of the circuit section 164, a portion of the display section 162, a portion of the connection section 140, and a portion of the area including the end portion are cut away.

[0437] 21A includes transistors 205D, 205R, 205G, and 205B, a light-emitting element 130R, a light-emitting element 130G, and a light-emitting element 130B between a substrate 151 and a substrate 152. The light-emitting element 130R is a display element included in the sub-pixel 11R that emits red light, the light-emitting element 130G is a display element included in the sub-pixel 11G that emits green light, and the light-emitting element 130B is a display element included in the sub-pixel 11B that emits blue light.

[0438] The display device 50A employs an SBS structure, which allows the materials and configuration to be optimized for each light-emitting element, increasing the degree of freedom in the selection of materials and configurations and facilitating improvements in brightness and reliability.

[0439] The display device 50A is a top emission type, which allows transistors and the like to be arranged overlapping the light emitting region of the light emitting element, thereby enabling a higher pixel aperture ratio than a bottom emission type.

[0440] The transistors 205D, 205R, 205G, and 205B are all formed on the substrate 151. These transistors can be manufactured using the same material and the same process.

[0441] In this embodiment, an example in which OS transistors are used as the transistors 205D, 205R, 205G, and 205B will be described. The transistors according to one embodiment of the present invention can be used as the transistors 205D, 205R, 205G, and 205B. That is, the display device 50A includes the transistor according to one embodiment of the present invention in both the display portion 162 and the circuit portion 164. By using the transistor according to one embodiment of the present invention in the display portion 162, the pixel size can be reduced, leading to higher resolution. Furthermore, by using the transistor according to one embodiment of the present invention in the circuit portion 164, the area occupied by the circuit portion 164 can be reduced, leading to a narrower frame. The description of the previous embodiment can be referred to for the transistor according to one embodiment of the present invention.

[0442] Specifically, the transistors 205D, 205R, 205G, and 205B each include a conductive layer 104 that functions as a gate, an insulating layer 106 that functions as a gate insulating layer, conductive layers 112a and 112b that function as a source and a drain, a semiconductor layer 108 containing metal oxide, a conductive layer 103 in contact with the conductive layer 112a and the semiconductor layer 108, and an insulating layer 110 (insulating layers 110a, 110b, and 110c). Here, the same hatched pattern is applied to multiple layers obtained by processing the same conductive film. The insulating layer 110 is located between the conductive layer 112a and the semiconductor layer 108. The insulating layer 106 is located between the conductive layer 104 and the semiconductor layer 108.

[0443] Note that the transistor included in the display device of this embodiment is not limited to the transistor of one embodiment of the present invention. For example, the display device may include a combination of the transistor of one embodiment of the present invention and a transistor having another structure.

[0444] The display device of this embodiment may include, for example, one or more of a planar transistor, a staggered transistor, and an inverted staggered transistor. The transistor included in the display device of this embodiment may be either a top-gate transistor or a bottom-gate transistor. Alternatively, gates may be provided above and below a semiconductor layer in which a channel is formed.

[0445] The display device of this embodiment may also include a Si transistor.

[0446] To increase the emission luminance of a light-emitting element included in a pixel circuit, it is necessary to increase the amount of current flowing through the light-emitting element. To achieve this, it is necessary to increase the source-drain voltage of a driving transistor included in the pixel circuit. Since an OS transistor has a higher withstand voltage between its source and drain than a Si transistor, a high voltage can be applied between the source and drain of the OS transistor. Therefore, by using an OS transistor as the driving transistor included in a pixel circuit, it is possible to increase the amount of current flowing through the light-emitting element and increase the emission luminance of the light-emitting element.

[0447] Furthermore, when a transistor operates in a saturation region, an OS transistor can reduce the change in source-drain current with respect to a change in gate-source voltage compared to a Si transistor. Therefore, by using an OS transistor as a driving transistor included in a pixel circuit, the current flowing between the source and drain can be precisely controlled by changing the gate-source voltage, thereby controlling the amount of current flowing to a light-emitting element. This allows a pixel circuit to have a larger number of gray levels.

[0448] Furthermore, in terms of saturation characteristics of the current that flows when a transistor operates in a saturation region, an OS transistor can pass a more stable current (saturation current) than a Si transistor, even when the source-drain voltage gradually increases. Therefore, by using an OS transistor as a driving transistor, a stable current can be passed to a light-emitting element, even when the current-voltage characteristics of the light-emitting element vary. In other words, when an OS transistor operates in a saturation region, the source-drain current of the OS transistor remains almost unchanged even when the source-drain voltage is changed, thereby stabilizing the light-emitting luminance of the light-emitting element.

[0449] The transistors included in the circuit portion 164 and the transistors included in the display portion 162 may have the same structure or different structures. The transistors included in the circuit portion 164 may all have the same structure or may have two or more types. Similarly, the transistors included in the display portion 162 may all have the same structure or may have two or more types.

[0450] All the transistors included in the display portion 162 may be OS transistors, all the transistors included in the display portion 162 may be Si transistors, or some of the transistors included in the display portion 162 may be OS transistors and the rest may be Si transistors.

[0451] For example, by using both an LTPS transistor and an OS transistor in the display portion 162, a display device with low power consumption and high driving capability can be realized. A structure in which an LTPS transistor and an OS transistor are combined is sometimes referred to as LTPO. Note that a more preferable example is a structure in which an OS transistor is used as a transistor that functions as a switch for controlling conduction / non-conduction between wirings, and an LTPS transistor is used as a transistor for controlling current.

[0452] For example, one of the transistors included in the display portion 162 functions as a transistor for controlling a current flowing to a light-emitting element and can also be called a driving transistor. One of the source and drain of the driving transistor is electrically connected to a pixel electrode of the light-emitting element. The driving transistor is preferably an LTPS transistor. This can increase the current flowing to the light-emitting element in the pixel circuit.

[0453] On the other hand, another transistor included in the display portion 162 functions as a switch for controlling pixel selection / non-selection and can also be called a selection transistor. The gate of the selection transistor is electrically connected to a gate line, and one of the source and drain is electrically connected to a source line (signal line). An OS transistor is preferably used as the selection transistor. This allows the gradation of a pixel to be maintained even when the frame frequency is significantly reduced (for example, 1 fps or less). Therefore, power consumption can be reduced by stopping the driver when displaying a still image.

[0454] An insulating layer 218 is provided to cover the transistors 205D, 205R, 205G, and 205B, and an insulating layer 235 is provided over the insulating layer 218.

[0455] The insulating layer 218 preferably functions as a protective layer for the transistor. The insulating layer 218 is preferably made of a material through which impurities such as water and hydrogen are less likely to diffuse. This allows the insulating layer 218 to function as a barrier layer. With such a structure, diffusion of impurities from the outside into the transistor can be effectively suppressed, and the reliability of the display device can be improved.

[0456] The insulating layer 218 preferably includes one or more inorganic insulating films. Examples of the inorganic insulating film include an insulating oxide film, an insulating nitride film, an insulating oxynitride film, and an insulating nitride oxide film. Specific examples of these inorganic insulating films are as described above.

[0457] The insulating layer 235 preferably functions as a planarization layer, and is preferably an organic insulating film. Materials that can be used for the organic insulating film include acrylic resin, polyimide resin, epoxy resin, polyamide resin, polyimideamide resin, siloxane resin, benzocyclobutene resin, phenolic resin, and precursors of these resins. The insulating layer 235 may also have a laminated structure of an organic insulating film and an inorganic insulating film. The outermost layer of the insulating layer 235 preferably functions as an etching protection layer. This prevents recesses from being formed in the insulating layer 235 during processing of the pixel electrodes 111R, 111G, 111B, etc. Alternatively, recesses may be formed in the insulating layer 235 during processing of the pixel electrodes 111R, 111G, 111B, etc.

[0458] On the insulating layer 235, the light emitting elements 130R, 130G, and 130B are provided.

[0459] The light-emitting element 130R has a pixel electrode 111R on the insulating layer 235, an EL layer 113R on the pixel electrode 111R, and a common electrode 115 on the EL layer 113R. The light-emitting element 130R shown in Fig. 21A emits red light (R). The EL layer 113R has a light-emitting layer that emits red light.

[0460] The light-emitting element 130G has a pixel electrode 111G on the insulating layer 235, an EL layer 113G on the pixel electrode 111G, and a common electrode 115 on the EL layer 113G. The light-emitting element 130G shown in Fig. 21A emits green light (G). The EL layer 113G has a light-emitting layer that emits green light.

[0461] The light-emitting element 130B has a pixel electrode 111B on the insulating layer 235, an EL layer 113B on the pixel electrode 111B, and a common electrode 115 on the EL layer 113B. The light-emitting element 130B shown in Fig. 21A emits blue light (B). The EL layer 113B has a light-emitting layer that emits blue light.

[0462] 21A, the EL layers 113R, 113G, and 113B are all shown with the same film thickness, but this is not limited thereto. The EL layers 113R, 113G, and 113B may have different film thicknesses. For example, it is preferable to set the film thickness of the EL layers 113R, 113G, and 113B according to the optical path length that intensifies the light emitted by each layer. This allows for a microcavity structure to be realized, and the color purity of the light emitted from each light-emitting element to be improved.

[0463] The pixel electrode 111R is electrically connected to the conductive layer 112b of the transistor 205R through openings provided in the insulating layer 106, the insulating layer 218, and the insulating layer 235. Similarly, the pixel electrode 111G is electrically connected to the conductive layer 112b of the transistor 205G, and the pixel electrode 111B is electrically connected to the conductive layer 112b of the transistor 205B.

[0464] Ends of each of the pixel electrodes 111R, 111G, and 111B are covered with an insulating layer 237. The insulating layer 237 functions as a partition wall. The insulating layer 237 can be formed in a single layer structure or a stacked layer structure using one or both of an inorganic insulating material and an organic insulating material. For example, the materials that can be used for the insulating layer 218 and the insulating layer 235 can be used for the insulating layer 237. The insulating layer 237 can electrically insulate the pixel electrode and the common electrode. Furthermore, the insulating layer 237 can electrically insulate adjacent light-emitting elements from each other.

[0465] The insulating layer 237 is provided at least in the display unit 162. The insulating layer 237 may be provided not only in the display unit 162 but also in the connection unit 140 and the circuit unit 164. Furthermore, the insulating layer 237 may be provided up to the edge of the display device 50A.

[0466] The common electrode 115 is a continuous film provided in common to the light-emitting elements 130R, 130G, and 130B. The common electrode 115 shared by the plurality of light-emitting elements is electrically connected to a conductive layer 123 provided in the connection portion 140. The conductive layer 123 is preferably formed using the same material and in the same process as the pixel electrodes 111R, 111G, and 111B.

[0467] In a display device according to one embodiment of the present invention, a conductive film that transmits visible light is preferably used for the pixel electrode and the common electrode, which are electrodes from which light is extracted, and a conductive film that reflects visible light is preferably used for the electrode from which light is not extracted.

[0468] A conductive film that transmits visible light may also be used for the electrode on the side from which light is not extracted. In this case, it is preferable to place the electrode between the reflective layer and the EL layer. That is, the light emitted from the EL layer may be reflected by the reflective layer and extracted from the display device.

[0469] Materials for forming the pair of electrodes of the light-emitting element can include metals, alloys, electrically conductive compounds, and mixtures thereof. Specific examples of such materials include metals such as aluminum, magnesium, titanium, chromium, manganese, iron, cobalt, nickel, copper, gallium, zinc, indium, tin, molybdenum, tantalum, tungsten, palladium, gold, platinum, silver, yttrium, and neodymium, as well as alloys containing these metals in combination. Examples of such materials include indium tin oxide (In-Sn oxide, also referred to as ITO), In-Si-Sn oxide (also referred to as ITSO), indium zinc oxide (In-Zn oxide), and In-W-Zn oxide. Examples of such materials include aluminum-containing alloys (aluminum alloys), such as an alloy of aluminum, nickel, and lanthanum (Al-Ni-La), and silver-containing alloys, such as an alloy of silver and magnesium and an alloy of silver, palladium, and copper (Ag-Pd-Cu, also referred to as APC). Other examples of the material include elements belonging to Group 1 or 2 of the periodic table (e.g., lithium, cesium, calcium, and strontium) that are not listed above as examples, rare earth metals such as europium and ytterbium, alloys containing appropriate combinations of these, and graphene.

[0470] The light-emitting element preferably has a micro-optical resonator (microcavity) structure. Therefore, one of the pair of electrodes of the light-emitting element preferably has an electrode that is transparent and reflective to visible light (semi-transmissive / semi-reflective electrode), and the other preferably has an electrode that is reflective to visible light (reflective electrode). By having the light-emitting element have a microcavity structure, the light emitted from the light-emitting layer can be resonated between both electrodes, thereby intensifying the light emitted from the light-emitting element.

[0471] The light transmittance of the transparent electrode is 40% or more. For example, it is preferable to use an electrode having a visible light (light with a wavelength of 400 nm or more and less than 750 nm) transmittance of 40% or more for the transparent electrode of the light-emitting element. The visible light reflectance of the semi-transmissive / semi-reflective electrode is 10% or more and 95% or less, preferably 30% or more and 80% or less. The visible light reflectance of the reflective electrode is 40% or more and 100% or less, preferably 70% or more and 100% or less. Furthermore, the resistivity of these electrodes is 1×10 −２ Preferably, it is Ωcm or less.

[0472] The EL layers 113R, 113G, and 113B are each provided in an island shape. In FIG. 21A , the ends of adjacent EL layers 113R and 113G overlap, the ends of adjacent EL layers 113G and 113B overlap, and the ends of adjacent EL layers 113R and 113B overlap. When forming island-shaped EL layers using a fine metal mask, the ends of adjacent EL layers may overlap as shown in FIG. 21A , but this is not limited to this. In other words, adjacent EL layers may not overlap but may be spaced apart. Furthermore, the display device may have both overlapping portions between adjacent EL layers and portions between adjacent EL layers that do not overlap but are spaced apart.

[0473] Each of the EL layers 113R, 113G, and 113B includes at least a light-emitting layer. The light-emitting layer includes one or more light-emitting materials. As the light-emitting material, a material that emits light of a color such as blue, purple, blue-purple, green, yellow-green, yellow, orange, or red is appropriately used. Furthermore, a material that emits near-infrared light can also be used as the light-emitting material.

[0474] The light-emitting material may include a fluorescent material, a phosphorescent material, a TADF material, and a quantum dot material.

[0475] The light-emitting layer may contain one or more organic compounds (host materials, assist materials, etc.) in addition to a light-emitting substance (guest material). As the one or more organic compounds, one or both of a substance with high hole-transport properties (hole-transport material) and a substance with high electron-transport properties (electron-transport material) can be used. Furthermore, as the one or more organic compounds, a bipolar substance (a substance with high electron-transport properties and high hole-transport properties) or a TADF material can be used.

[0476] The light-emitting layer preferably includes, for example, a phosphorescent material and a hole-transporting material and an electron-transporting material, which are a combination that easily forms an exciplex. This configuration allows efficient emission using Exciplex-Triple Energy Transfer (ExTET), which is energy transfer from the exciplex to the light-emitting material (phosphorescent material). By selecting a combination that forms an exciplex that emits light that overlaps with the wavelength of the lowest-energy absorption band of the light-emitting material, energy transfer becomes smooth, allowing efficient emission. This configuration simultaneously enables high efficiency, low-voltage operation, and long life of the light-emitting element.

[0477] In addition to the light-emitting layer, the EL layer may include one or more of a layer containing a substance with high hole-injecting properties (hole-injecting layer), a layer containing a hole-transporting material (hole-transporting layer), a layer containing a substance with high electron-blocking properties (electron-blocking layer), a layer containing a substance with high electron-injecting properties (electron-injecting layer), a layer containing an electron-transporting material (electron-transporting layer), and a layer containing a substance with high hole-blocking properties (hole-blocking layer).In addition, the EL layer may include one or both of a bipolar substance and a TADF material.

[0478] The light-emitting element can be made of either a low-molecular-weight compound or a high-molecular-weight compound, and may contain an inorganic compound. The layers constituting the light-emitting element can be formed by a method such as a vapor deposition method (including a vacuum vapor deposition method), a transfer method, a printing method, an inkjet method, or a coating method.

[0479] The light-emitting element may have a single structure (a structure having only one light-emitting unit) or a tandem structure (a structure having multiple light-emitting units). The light-emitting unit has at least one light-emitting layer. The tandem structure is a structure in which multiple light-emitting units are connected in series via a charge-generating layer. When a voltage is applied between a pair of electrodes, the charge-generating layer injects electrons into one of the two light-emitting units and holes into the other. The tandem structure allows the light-emitting element to emit light with high brightness. Furthermore, the tandem structure can reduce the current required to achieve the same brightness compared to a single structure, thereby improving reliability. The tandem structure may also be called a stack structure.

[0480] In Figure 21A, when light-emitting elements with a tandem structure are used, it is preferable that EL layer 113R has a structure having multiple light-emitting units that emit red light, EL layer 113G has a structure having multiple light-emitting units that emit green light, and EL layer 113B has a structure having multiple light-emitting units that emit blue light.

[0481] A protective layer 131 is provided on the light-emitting elements 130R, 130G, and 130B. The protective layer 131 and the substrate 152 are bonded via an adhesive layer 142. A light-shielding layer 117 is provided on the substrate 152. For example, a solid sealing structure or a hollow sealing structure can be applied to seal the light-emitting elements. In FIG. 21A , the space between the substrates 152 and 151 is filled with the adhesive layer 142, and a solid sealing structure is applied. Alternatively, the space may be filled with an inert gas (such as nitrogen or argon), and a hollow sealing structure may be applied. In this case, the adhesive layer 142 may be provided so as not to overlap with the light-emitting elements. Alternatively, the space may be filled with a resin different from the frame-shaped adhesive layer 142.

[0482] The protective layer 131 is preferably provided on at least the display unit 162, and is preferably provided so as to cover the entire display unit 162. The protective layer 131 is preferably provided so as to cover not only the display unit 162, but also the connection unit 140 and the circuit unit 164. The protective layer 131 is preferably provided up to the edge of the display device 50A. On the other hand, in the connection unit 204, the FPC 172 and the conductive layer 166 are electrically connected to each other, so that a portion where the protective layer 131 is not provided is generated.

[0483] By providing the protective layer 131 on the light emitting elements 130R, 130G, and 130B, the reliability of the light emitting elements can be improved.

[0484] The protective layer 131 may have a single layer structure or a stacked structure of two or more layers. The conductivity of the protective layer 131 does not matter. The protective layer 131 can be formed of at least one of an insulating film, a semiconductor film, and a conductive film.

[0485] The protective layer 131 has an inorganic film, which can prevent oxidation of the common electrode 115, prevent impurities (moisture, oxygen, etc.) from entering the light-emitting element, and so on, thereby suppressing deterioration of the light-emitting element and improving the reliability of the display device.

[0486] For the protective layer 131, for example, an inorganic insulating film such as an insulating oxide film, an insulating nitride film, an insulating oxynitride film, or an insulating nitride oxide film can be used. Specific examples of these inorganic insulating films are as described above. In particular, the protective layer 131 preferably includes an insulating nitride film or an insulating nitride oxide film, and more preferably includes an insulating nitride film.

[0487] Alternatively, an inorganic film containing ITO, In—Zn oxide, Ga—Zn oxide, Al—Zn oxide, IGZO, or the like may be used for the protective layer 131. The inorganic film preferably has high resistance, specifically, preferably has higher resistance than the common electrode 115. The inorganic film may further contain nitrogen.

[0488] When light emitted from the light-emitting element is extracted through the protective layer 131, it is preferable that the protective layer 131 has high transparency to visible light. For example, ITO, IGZO, and aluminum oxide are preferable because they are inorganic materials that have high transparency to visible light.

[0489] For example, a stacked structure of an aluminum oxide film and a silicon nitride film on the aluminum oxide film, or a stacked structure of an aluminum oxide film and an IGZO film on the aluminum oxide film can be used as the protective layer 131. By using such a stacked structure, impurities (water, oxygen, etc.) can be prevented from entering the EL layer side.

[0490] Furthermore, the protective layer 131 may have an organic film. For example, the protective layer 131 may have both an organic film and an inorganic film. Examples of organic films that can be used for the protective layer 131 include the organic insulating films that can be used for the insulating layer 235.

[0491] A connection portion 204 is provided in a region of the substrate 151 where the substrate 152 does not overlap. In the connection portion 204, a conductive layer 165 is electrically connected to the FPC 172 via a conductive layer 166 and a connection layer 242. In this example, the conductive layer 165 is a conductive layer obtained by processing the same conductive film as the conductive layer 112b. In this example, the conductive layer 166 is a conductive layer obtained by processing the same conductive film as the pixel electrodes 111R, 111G, and 111B. The conductive layer 166 is exposed on the top surface of the connection portion 204. This allows the connection portion 204 and the FPC 172 to be electrically connected via the connection layer 242.

[0492] The display device 50A is a top-emission type. Light emitted by the light-emitting elements is emitted toward the substrate 152. The substrate 152 is preferably made of a material that is highly transparent to visible light. The pixel electrodes 111R, 111G, and 111B contain a material that reflects visible light, and the counter electrode (common electrode 115) contains a material that transmits visible light.

[0493] It is preferable to provide a light-shielding layer 117 on the surface of the substrate 152 facing the substrate 151. The light-shielding layer 117 can be provided between adjacent light-emitting elements, in the connection section 140, in the circuit section 164, and the like.

[0494] Furthermore, a colored layer such as a color filter may be provided on the surface of the substrate 152 on the substrate 151 side or on the protective layer 131. When a color filter is provided over the light-emitting element, the color purity of light emitted from the pixel can be increased.

[0495] The colored layer is a colored layer that selectively transmits light in a specific wavelength range and absorbs light in other wavelength ranges. For example, a red (R) color filter that transmits light in the red wavelength range, a green (G) color filter that transmits light in the green wavelength range, and a blue (B) color filter that transmits light in the blue wavelength range can be used. Each colored layer can be made of one or more of a metal material, a resin material, a pigment, and a dye. The colored layers are formed at desired positions by a printing method, an inkjet method, an etching method using photolithography, or the like.

[0496] Various optical members can be disposed on the outer side of the substrate 152 (the surface opposite to the substrate 151). Examples of optical members include a polarizing plate, a retardation plate, a light diffusion layer (such as a diffusion film), an anti-reflection layer, and a light-collecting film. Furthermore, a surface protection layer such as an anti-static film that suppresses the adhesion of dust, a water-repellent film that makes it difficult for dirt to adhere, a hard coat film that suppresses the occurrence of scratches during use, or an impact absorbing layer may be disposed on the outer side of the substrate 152. For example, a glass layer or a silica layer (SiO ｘ The surface protection layer can be preferably formed of a material such as DLC (diamond-like carbon), aluminum oxide (AlO ｘ ), polyester-based materials, or polycarbonate-based materials may also be used. Note that it is preferable to use a material with high transmittance to visible light for the surface protection layer. It is also preferable to use a material with high hardness for the surface protection layer.

[0497] The substrate 151 and the substrate 152 can each be made of glass, quartz, ceramics, sapphire, resin, metal, alloy, semiconductor, or the like. A material that transmits light is used for the substrate on the side from which light from the light-emitting element is extracted. When a flexible material is used for the substrate 151 and the substrate 152, the flexibility of the display device can be increased, and a flexible display can be realized. Furthermore, a polarizing plate may be used for at least one of the substrates 151 and 152.

[0498] Substrates 151 and 152 may each be made of polyester resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyacrylonitrile resin, acrylic resin, polyimide resin, polymethyl methacrylate resin, polycarbonate (PC) resin, polyethersulfone (PES) resin, polyamide resin (nylon, aramid, etc.), polysiloxane resin, cycloolefin resin, polystyrene resin, polyamideimide resin, polyurethane resin, polyvinyl chloride resin, polyvinylidene chloride resin, polypropylene resin, polytetrafluoroethylene (PTFE) resin, ABS resin, cellulose nanofiber, etc. At least one of substrates 151 and 152 may be made of glass having a thickness sufficient to provide flexibility.

[0499] When a circularly polarizing plate is superimposed on a display device, it is preferable that the display device has a substrate with high optical isotropy. A substrate with high optical isotropy has low birefringence (it can also be said that the amount of birefringence is small). Examples of films with high optical isotropy include triacetyl cellulose (TAC, also known as cellulose triacetate) films, cycloolefin polymer (COP) films, cycloolefin copolymer (COC) films, and acrylic films.

[0500] The adhesive layer 142 can be made of various curable adhesives, such as a photo-curable adhesive (e.g., an ultraviolet curable adhesive), a reactive curable adhesive, a thermosetting adhesive, or an anaerobic adhesive. Examples of such adhesives include epoxy resin, acrylic resin, silicone resin, phenolic resin, polyimide resin, imide resin, PVC (polyvinyl chloride) resin, PVB (polyvinyl butyral) resin, and EVA (ethylene vinyl acetate) resin. In particular, a material with low moisture permeability, such as epoxy resin, is preferable. Alternatively, a two-component resin may be used. Alternatively, an adhesive sheet or the like may be used.

[0501] The connection layer 242 may be an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like.

[0502] [Display Device 50B] Figure 21B shows an example of a cross section of the display unit 162 of the display device 50B. The display device 50B differs from the display device 50A mainly in that each subpixel of each color uses a light-emitting element having a common EL layer 113 and a colored layer (such as a color filter). The configuration shown in Figure 21B can be combined with the region including the FPC 172, the circuit portion 164, the stacked structure from the substrate 151 to the insulating layer 235 of the display unit 162, the connection portion 140, and the end portion configuration shown in Figure 21A. Note that in the following description of the display device, descriptions of parts similar to those of the display device described above may be omitted.

[0503] A display device 50B shown in FIG. 21B includes light-emitting elements 130R, 130G, and 130B, a colored layer 132R that transmits red light, a colored layer 132G that transmits green light, and a colored layer 132B that transmits blue light.

[0504] The light emitting element 130R has a pixel electrode 111R, an EL layer 113 on the pixel electrode 111R, and a common electrode 115 on the EL layer 113. The light emitted from the light emitting element 130R is extracted as red light to the outside of the display device 50B via the colored layer 132R.

[0505] The light emitting element 130G has a pixel electrode 111G, an EL layer 113 on the pixel electrode 111G, and a common electrode 115 on the EL layer 113. Light emitted from the light emitting element 130G is extracted as green light to the outside of the display device 50B via the colored layer 132G.

[0506] The light emitting element 130B has a pixel electrode 111B, an EL layer 113 on the pixel electrode 111B, and a common electrode 115 on the EL layer 113. Light emitted from the light emitting element 130B is extracted as blue light to the outside of the display device 50B via the colored layer 132B.

[0507] The light-emitting elements 130R, 130G, and 130B each share the EL layer 113 and the common electrode 115. The configuration in which the subpixels of each color are provided with a common EL layer 113 can reduce the number of manufacturing steps compared to the configuration in which the subpixels of each color are provided with different EL layers.

[0508] 21B emit white light. The white light emitted by the light emitting elements 130R, 130G, and 130B passes through the colored layers 132R, 132G, and 132B, thereby obtaining light of a desired color.

[0509] A light-emitting element that emits white light preferably includes two or more light-emitting layers. When two light-emitting layers are used to obtain white light emission, light-emitting layers may be selected such that the emission colors of the two light-emitting layers have a complementary color relationship. For example, by making the emission color of the first light-emitting layer and the emission color of the second light-emitting layer have a complementary color relationship, a configuration in which the light-emitting element as a whole emits white light can be obtained. Furthermore, when three or more light-emitting layers are used to obtain white light emission, the emission colors of the three or more light-emitting layers may be combined to form a configuration in which the light-emitting element as a whole emits white light.

[0510] The EL layer 113 preferably includes, for example, a light-emitting layer having a light-emitting substance that emits blue light and a light-emitting layer having a light-emitting substance that emits visible light with a wavelength longer than blue. The EL layer 113 preferably includes, for example, a light-emitting layer that emits yellow light and a light-emitting layer that emits blue light. Alternatively, the EL layer 113 preferably includes, for example, a light-emitting layer that emits red light, a light-emitting layer that emits green light, and a light-emitting layer that emits blue light.

[0511] A tandem structure is preferably used for the light-emitting element emitting white light. Specifically, a two-stage tandem structure having a light-emitting unit that emits yellow light and a light-emitting unit that emits blue light, a two-stage tandem structure having a light-emitting unit that emits red and green light and a light-emitting unit that emits blue light, a three-stage tandem structure having a light-emitting unit that emits blue light, a light-emitting unit that emits yellow, yellow-green, or green light, and a light-emitting unit that emits blue light, in this order, or a three-stage tandem structure having a light-emitting unit that emits blue light, a light-emitting unit that emits yellow, yellow-green, or green light, and red light, and a light-emitting unit that emits blue light, in this order, or the like can be applied. For example, the number of layers of the light-emitting units and the order of the colors can be, from the anode side, a two-layer structure of B and Y, a two-layer structure of B and light-emitting unit X, a three-layer structure of B, Y, and B, and the number of layers of the light-emitting layers in light-emitting unit X and the order of the colors can be, from the anode side, a two-layer structure of R and Y, a two-layer structure of R and G, a two-layer structure of G and R, a three-layer structure of G, R, and G, or a three-layer structure of R, G, and R. Furthermore, another layer can be provided between the two light-emitting layers.

[0512] By applying a microcavity structure, a light emitting element configured to emit white light may emit light of a specific wavelength such as red, green, or blue that is intensified.

[0513] Alternatively, for example, the light-emitting elements 130R, 130G, and 130B shown in FIG. 21B emit blue light. In this case, the EL layer 113 includes one or more light-emitting layers that emit blue light. In the sub-pixel 11B that emits blue light, the blue light emitted by the light-emitting element 130B can be extracted. Furthermore, in the sub-pixel 11R that emits red light and the sub-pixel 11G that emits green light, a color conversion layer can be provided between the light-emitting element 130R or light-emitting element 130G and the substrate 152 to convert the blue light emitted by the light-emitting element 130R or light-emitting element 130G into light with a longer wavelength, thereby extracting red or green light. Furthermore, it is preferable to provide a coloring layer 132R between the color conversion layer and the substrate 152 on the light-emitting element 130R, and a coloring layer 132G between the color conversion layer and the substrate 152 on the light-emitting element 130G. A portion of the light emitted by the light-emitting element may be transmitted directly without being converted by the color conversion layer. By extracting the light transmitted through the color conversion layer via the colored layer, light other than the desired color can be absorbed by the colored layer, thereby increasing the color purity of the light emitted by the sub-pixel.

[0514] [Display Device 50C] A display device 50C shown in FIG. 22 differs from the display device 50B mainly in that it is a bottom-emission display device.

[0515] Light emitted from the light-emitting element is emitted toward the substrate 151. A material that is highly transparent to visible light is preferably used for the substrate 151. On the other hand, the light-transmitting property of a material used for the substrate 152 does not matter.

[0516] 22 shows an example in which the light-shielding layer 117 is provided over the substrate 151, the insulating layer 153 is provided over the light-shielding layer 117, and the transistors 205D, 205R (not shown), 205G, and 205B are provided over the insulating layer 153. In addition, the coloring layers 132R, 132G, and 132B are provided over the insulating layer 218, and the insulating layer 235 is provided over the coloring layers 132R, 132G, and 132B.

[0517] The light emitting element 130R overlapping the colored layer 132R includes a pixel electrode 111R, an EL layer 113, and a common electrode 115.

[0518] The light emitting element 130G overlapping the colored layer 132G includes a pixel electrode 111G, an EL layer 113, and a common electrode 115.

[0519] The light emitting element 130B overlapping the colored layer 132B has a pixel electrode 111B, an EL layer 113 and a common electrode 115.

[0520] The pixel electrodes 111R, 111G, and 111B are each made of a material that is highly transparent to visible light. It is preferable to use a material that reflects visible light for the common electrode 115. In a bottom-emission display device, a low-resistance metal or the like can be used for the common electrode 115, which can suppress voltage drops caused by the resistance of the common electrode 115 and achieve high display quality.

[0521] The transistor of one embodiment of the present invention can be miniaturized and its occupation area can be reduced; therefore, in a bottom-emission display device, the aperture ratio of a pixel can be increased or the pixel size can be reduced.

[0522] [Display Device 50D] A display device 50D shown in FIG. 23A differs from the display device 50A mainly in that it has a light receiving element 130S.

[0523] The display device 50D has a light-emitting element and a light-receiving element in each pixel. In the display device 50D, it is preferable to use an organic EL element as the light-emitting element and an organic photodiode as the light-receiving element. The organic EL element and the organic photodiode can be formed on the same substrate. Therefore, an organic photodiode can be built into a display device using an organic EL element.

[0524] In the display device 50D, in which pixels have a light-emitting element and a light-receiving element, the pixels have a light-receiving function, so that it is possible to detect contact or proximity of an object while displaying an image. Therefore, the display unit 162 has one or both of an imaging function and a sensing function in addition to an image display function. For example, in addition to displaying an image using all of the sub-pixels of the display device 50D, it is also possible for some sub-pixels to emit light as a light source, other sub-pixels to perform light detection, and the remaining sub-pixels to display an image.

[0525] Therefore, there is no need to provide a light receiving unit and a light source separately from the display device 50D, and the number of components in the electronic device can be reduced. For example, there is no need to provide a separate biometric authentication device or a capacitive touch panel for scrolling, etc. Therefore, by using the display device 50D, it is possible to provide an electronic device with reduced manufacturing costs.

[0526] When a light receiving element is used as an image sensor, the display device 50D can capture an image using the light receiving element. For example, the image sensor can capture an image for personal authentication using a fingerprint, palm print, iris, pulse shape (including vein shape and artery shape), face, or the like.

[0527] The light receiving element can be used as a touch sensor (also called a direct touch sensor) or a non-contact sensor (also called a hover sensor, hover touch sensor, or touchless sensor). A touch sensor can detect an object (such as a finger, hand, or pen) when the object comes into direct contact with the display device. A non-contact sensor can detect an object without the object touching the display device.

[0528] The light receiving element 130S has a pixel electrode 111S on an insulating layer 235, a functional layer 113S on the pixel electrode 111S, and a common electrode 115 on the functional layer 113S. Light Lin is incident on the functional layer 113S from outside the display device 50D.

[0529] The pixel electrode 111S is electrically connected to the conductive layer 112b of the transistor 205S through openings provided in the insulating layer 106, the insulating layer 218, and the insulating layer 235.

[0530] The end of the pixel electrode 111S is covered with an insulating layer 237.

[0531] The common electrode 115 is a continuous film provided in common to the light receiving element 130S, the light emitting element 130R (not shown), the light emitting element 130G, and the light emitting element 130B. The common electrode 115 shared by the light emitting element and the light receiving element is electrically connected to the conductive layer 123 provided in the connection portion 140.

[0532] The functional layer 113S has at least an active layer (also referred to as a photoelectric conversion layer). The active layer includes a semiconductor. Examples of the semiconductor include inorganic semiconductors such as silicon and organic semiconductors including organic compounds. In this embodiment, an example in which an organic semiconductor is used as the semiconductor included in the active layer is shown. Using an organic semiconductor is preferable because the light-emitting layer and the active layer can be formed by the same method (for example, vacuum deposition), allowing common use of manufacturing equipment.

[0533] The functional layer 113S may further include a layer containing a substance with high hole transporting properties, a substance with high electron transporting properties, a bipolar substance, or the like, as a layer other than the active layer. Furthermore, without being limited to the above, the functional layer 113S may further include a layer containing a substance with high hole injection properties, a hole blocking material, a substance with high electron injection properties, an electron blocking material, or the like. For example, the materials that can be used for the light-emitting element described above can be used for the functional layer 113S.

[0534] The light-receiving element can be made of either a low-molecular-weight compound or a high-molecular-weight compound, and may contain an inorganic compound. The layers constituting the light-receiving element can be formed by a method such as vapor deposition (including vacuum vapor deposition), transfer, printing, inkjet printing, or coating.

[0535] A display device 50D shown in FIGS. 23B and 23C has, between a substrate 151 and a substrate 152, a layer 353 having a light receiving element, a circuit layer 355, and a layer 357 having a light emitting element.

[0536] The layer 353 includes, for example, the light receiving element 130S. The layer 357 includes, for example, the light emitting elements 130R, 130G, and 130B.

[0537] The circuit layer 355 includes a circuit for driving the light receiving element and a circuit for driving the light emitting element. The circuit layer 355 includes, for example, transistors 205R, 205G, and 205B. In addition, the circuit layer 355 may include one or more of a switch, a capacitor, a resistor, a wiring, a terminal, and the like.

[0538] 23B shows an example in which the light receiving element 130S is used as a touch sensor. As shown in FIG. 23B, light emitted by the light emitting element in layer 357 is reflected by a finger 352 that touches the display device 50D, and the light receiving element in layer 353 detects the reflected light. This makes it possible to detect that the finger 352 has touched the display device 50D.

[0539] 23C shows an example in which the light receiving element 130S is used as a non-contact sensor. As shown in FIG. 23C, light emitted by a light emitting element in a layer 357 is reflected by a finger 352 that is close to (i.e., not in contact with) the display device 50D, and the light receiving element in a layer 353 detects the reflected light.

[0540] 24A is an example of a display device employing an MML (metal maskless) structure. That is, the display device 50E has light-emitting elements fabricated without using a fine metal mask. The stacked structures from the substrate 151 to the insulating layer 235 and from the protective layer 131 to the substrate 152 are similar to those of the display device 50A, and therefore will not be described here.

[0541] In FIG. 24A, light emitting elements 130 R, 130 G, and 130 B are provided on an insulating layer 235 .

[0542] The light-emitting element 130R includes a conductive layer 124R on the insulating layer 235, a conductive layer 126R on the conductive layer 124R, a layer 133R on the conductive layer 126R, a common layer 114 on the layer 133R, and a common electrode 115 on the common layer 114. The light-emitting element 130R shown in FIG. 24A emits red light (R). The layer 133R includes a light-emitting layer that emits red light. In the light-emitting element 130R, the layer 133R and the common layer 114 can be collectively referred to as an EL layer. One or both of the conductive layer 124R and the conductive layer 126R can be referred to as a pixel electrode.

[0543] The light-emitting element 130G includes a conductive layer 124G on the insulating layer 235, a conductive layer 126G on the conductive layer 124G, a layer 133G on the conductive layer 126G, a common layer 114 on the layer 133G, and a common electrode 115 on the common layer 114. The light-emitting element 130G shown in FIG. 24A emits green light (G). The layer 133G includes a light-emitting layer that emits green light. In the light-emitting element 130G, the layer 133G and the common layer 114 can be collectively referred to as an EL layer. One or both of the conductive layer 124G and the conductive layer 126G can be referred to as a pixel electrode.

[0544] The light-emitting element 130B includes a conductive layer 124B on the insulating layer 235, a conductive layer 126B on the conductive layer 124B, a layer 133B on the conductive layer 126B, a common layer 114 on the layer 133B, and a common electrode 115 on the common layer 114. The light-emitting element 130B shown in FIG. 24A emits blue light (B). The layer 133B includes a light-emitting layer that emits blue light. In the light-emitting element 130B, the layer 133B and the common layer 114 can be collectively referred to as an EL layer. One or both of the conductive layer 124B and the conductive layer 126B can be referred to as a pixel electrode.

[0545] In this specification and the like, among the EL layers included in the light-emitting elements, layers provided in an island shape for each light-emitting element are referred to as layers 133B, 133G, or 133R, and a layer shared by a plurality of light-emitting elements is referred to as a common layer 114. Note that in this specification and the like, the layers 133R, 133G, and 133B may be referred to as island-shaped EL layers, EL layers formed in an island shape, or the like, without including the common layer 114.

[0546] The layers 133R, 133G, and 133B are spaced apart from one another. By providing an island-shaped EL layer for each light-emitting element, leakage current between adjacent light-emitting elements can be suppressed. This makes it possible to prevent unintended light emission due to crosstalk, and realize a display device with extremely high contrast.

[0547] 24A, the layers 133R, 133G, and 133B are all shown to have the same thickness, but this is not limitative and the layers 133R, 133G, and 133B may have different thicknesses.

[0548] The conductive layer 124R is electrically connected to the conductive layer 112b of the transistor 205R through openings provided in the insulating layer 106, the insulating layer 218, and the insulating layer 235. Similarly, the conductive layer 124G is electrically connected to the conductive layer 112b of the transistor 205G, and the conductive layer 124B is electrically connected to the conductive layer 112b of the transistor 205B.

[0549] The conductive layers 124R, 124G, and 124B are formed so as to cover the openings provided in the insulating layer 235. A layer 128 is buried in the recesses of the conductive layers 124R, 124G, and 124B, respectively.

[0550] The layer 128 has a function of planarizing the recesses of the conductive layers 124R, 124G, and 124B. Conductive layers 126R, 126G, and 126B, which are electrically connected to the conductive layers 124R, 124G, and 124B, are provided on the conductive layers 124R, 124G, and 124B and the layer 128. Therefore, the regions overlapping with the recesses of the conductive layers 124R, 124G, and 124B can also be used as light-emitting regions, thereby increasing the aperture ratio of the pixel. It is preferable to use a conductive layer that functions as a reflective electrode for the conductive layers 124R and 126R.

[0551] The layer 128 may be an insulating layer or a conductive layer. Various inorganic insulating materials, organic insulating materials, and conductive materials can be used as appropriate for the layer 128. In particular, the layer 128 is preferably formed using an insulating material, and more preferably using an organic insulating material. For example, the organic insulating material that can be used for the insulating layer 237 described above can be used for the layer 128.

[0552] 24A shows an example in which the top surface of layer 128 has a flat portion, but there are no particular limitations on the shape of layer 128. The top surface of layer 128 can have at least one of a convex curved surface, a concave curved surface, and a flat surface.

[0553] Furthermore, the height of the upper surface of layer 128 and the height of the upper surface of conductive layer 124R may be the same or approximately the same, or may be different from each other. For example, the height of the upper surface of layer 128 may be lower or higher than the height of the upper surface of conductive layer 124R.

[0554] The end of the conductive layer 126R may be flush with the end of the conductive layer 124R, or may cover the side surface of the end of the conductive layer 124R. The end of each of the conductive layers 124R and 126R preferably has a tapered shape. Specifically, the end of each of the conductive layers 124R and 126R preferably has a tapered shape with a taper angle greater than 0 degrees and less than 90 degrees. When the end of the pixel electrode has a tapered shape, the layer 133R provided along the side surface of the pixel electrode has an inclined portion. By tapering the side surface of the pixel electrode, the coverage of the EL layer provided along the side surface of the pixel electrode can be improved.

[0555] The conductive layers 124G, 126G and the conductive layers 124B, 126B are similar to the conductive layers 124R, 126R, and therefore detailed description thereof will be omitted.

[0556] The upper surface and side surfaces of the conductive layer 126R are covered with the layer 133R. Similarly, the upper surface and side surfaces of the conductive layer 126G are covered with the layer 133G, and the upper surface and side surfaces of the conductive layer 126B are covered with the layer 133B. Therefore, the entire region where the conductive layers 126R, 126G, and 126B are provided can be used as the light-emitting region of the light-emitting elements 130R, 130G, and 130B, thereby increasing the aperture ratio of the pixel.

[0557] Part of the top surface and side surfaces of each of the layers 133R, 133G, and 133B are covered with insulating layers 125 and 127. A common layer 114 is provided on the layers 133R, 133G, 133B, and insulating layers 125 and 127, and a common electrode 115 is provided on the common layer 114. The common layer 114 and the common electrode 115 are each a continuous film provided in common to a plurality of light-emitting elements.

[0558] In FIG. 24A , the insulating layer 237 shown in FIG. 21A and other figures is not provided between the conductive layer 126R and the layer 133R. That is, the display device 50E does not have an insulating layer (also called a partition, bank, spacer, or the like) that is in contact with the pixel electrode and covers the upper edge of the pixel electrode. This allows the distance between adjacent light-emitting elements to be extremely narrow. This allows a high-definition or high-resolution display device to be obtained. Furthermore, a mask for forming the insulating layer is not required, thereby reducing the manufacturing cost of the display device.

[0559] As described above, the layers 133R, 133G, and 133B each have a light-emitting layer. The layers 133R, 133G, and 133B each preferably have a light-emitting layer and a carrier transport layer (electron transport layer or hole transport layer) on the light-emitting layer. Alternatively, the layers 133R, 133G, and 133B each preferably have a light-emitting layer and a carrier block layer (hole block layer or electron block layer) on the light-emitting layer. Alternatively, the layers 133R, 133G, and 133B each preferably have a light-emitting layer, a carrier block layer on the light-emitting layer, and a carrier transport layer on the carrier block layer. Because the surfaces of the layers 133R, 133G, and 133B are exposed during the manufacturing process of the display device, providing one or both of a carrier transport layer and a carrier block layer on the light-emitting layer can prevent the light-emitting layer from being exposed to the outermost surface and reduce damage to the light-emitting layer. This can improve the reliability of the light-emitting element.

[0560] The common layer 114 includes, for example, an electron injection layer or a hole injection layer. Alternatively, the common layer 114 may include a stack of an electron transport layer and an electron injection layer, or a stack of a hole transport layer and a hole injection layer. The common layer 114 is shared by the light-emitting elements 130R, 130G, and 130B.

[0561] The side surfaces of the layers 133R, 133G, and 133B are covered with the insulating layer 125. The insulating layer 127 covers the side surfaces of the layers 133R, 133G, and 133B with the insulating layer 125 interposed therebetween.

[0562] The side surfaces (and even part of the upper surfaces) of the layers 133R, 133G, and 133B are covered with at least one of the insulating layer 125 and the insulating layer 127, which prevents the common layer 114 (or the common electrode 115) from coming into contact with the pixel electrodes and the side surfaces of the layers 133R, 133G, and 133B, thereby preventing short circuits in the light-emitting elements, thereby improving the reliability of the light-emitting elements.

[0563] The insulating layer 125 is preferably in contact with each side surface of the layer 133R, the layer 133G, and the layer 133B. By configuring the insulating layer 125 to be in contact with the layer 133R, the layer 133G, and the layer 133B, peeling of the layer 133R, the layer 133G, and the layer 133B can be prevented, and the reliability of the light-emitting element can be improved.

[0564] The insulating layer 127 is provided on the insulating layer 125 so as to fill the recesses in the insulating layer 125. The insulating layer 127 preferably covers at least a part of the side surface of the insulating layer 125.

[0565] By providing the insulating layers 125 and 127, the gaps between adjacent island-shaped layers can be filled, which reduces large unevenness in height on the surface on which layers (e.g., a carrier injection layer, a common electrode, etc.) are formed on the island-shaped layers, thereby making the surface flatter, thereby improving the coverage of the carrier injection layer, the common electrode, etc.

[0566] The common layer 114 and the common electrode 115 are provided over the layer 133R, the layer 133G, the layer 133B, the insulating layer 125, and the insulating layer 127. Before the insulating layer 125 and the insulating layer 127 are provided, a step is generated between a region where the pixel electrode and the island-shaped EL layer are provided and a region where the pixel electrode and the island-shaped EL layer are not provided (a region between light-emitting elements). In the display device of one embodiment of the present invention, the insulating layer 125 and the insulating layer 127 can flatten the step, thereby improving the coverage of the common layer 114 and the common electrode 115. Therefore, poor connection due to disconnection can be suppressed. Furthermore, the step can suppress an increase in electrical resistance due to a local thinning of the common electrode 115.

[0567] The upper surface of the insulating layer 127 preferably has a shape with high flatness. The upper surface of the insulating layer 127 may have at least one of a flat surface, a convex curved surface, and a concave curved surface. For example, the upper surface of the insulating layer 127 preferably has a convex curved surface shape with a large radius of curvature.

[0568] The insulating layer 125 can be an insulating layer containing an inorganic material. For example, an inorganic insulating film such as an insulating oxide film, a nitride insulating film, an oxynitride insulating film, or a nitride oxide insulating film can be used for the insulating layer 125. Specific examples of these inorganic insulating films are as described above. The insulating layer 125 may have a single-layer structure or a stacked-layer structure. Aluminum oxide is particularly preferable because it has a high etching selectivity with respect to the EL layer and protects the EL layer in the formation of the insulating layer 127 described later. By using an inorganic insulating film such as an aluminum oxide film, a hafnium oxide film, or a silicon oxide film formed by an ALD method as the insulating layer 125, the insulating layer 125 can be formed with fewer pinholes and excellent protection of the EL layer. The insulating layer 125 may also have a stacked-layer structure of a film formed by an ALD method and a film formed by a sputtering method. For example, the insulating layer 125 may have a stacked-layer structure of an aluminum oxide film formed by an ALD method and a silicon nitride film formed by a sputtering method.

[0569] The insulating layer 125 preferably functions as a barrier insulating layer against at least one of water and oxygen. The insulating layer 125 preferably has a function of suppressing diffusion of at least one of water and oxygen. The insulating layer 125 preferably has a function of capturing or fixing (also referred to as gettering) at least one of water and oxygen.

[0570] The insulating layer 125 has a function as a barrier insulating layer, which can suppress the entry of impurities (typically, at least one of water and oxygen) that may diffuse into each light-emitting element from the outside. With this structure, a highly reliable light-emitting element and a highly reliable display device can be provided.

[0571] The insulating layer 125 preferably has a low impurity concentration. This can prevent impurities from entering the EL layer from the insulating layer 125 and causing deterioration of the EL layer. Furthermore, a low impurity concentration in the insulating layer 125 can improve the barrier properties against at least one of water and oxygen. For example, it is desirable that the insulating layer 125 has a sufficiently low hydrogen concentration or a sufficiently low carbon concentration, or preferably both of them.

[0572] The insulating layer 127 provided on the insulating layer 125 has a function of flattening large unevenness of the insulating layer 125 formed between adjacent light-emitting elements. In other words, the insulating layer 127 has the effect of improving the flatness of the surface on which the common electrode 115 is formed.

[0573] An insulating layer containing an organic material can be suitably used as the insulating layer 127. As the organic material, a photosensitive resin is preferably used, and for example, a photosensitive resin composition containing an acrylic resin is preferably used. Note that in this specification and the like, the term "acrylic resin" does not refer only to polymethacrylic acid ester or methacrylic resin, but may refer to all acrylic polymers in a broad sense.

[0574] The insulating layer 127 may also be made of acrylic resin, polyimide resin, epoxy resin, imide resin, polyamide resin, polyimideamide resin, silicone resin, siloxane resin, benzocyclobutene-based resin, phenolic resin, or precursors of these resins. The insulating layer 127 may also be made of organic materials such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or alcohol-soluble polyamide resin. The photosensitive resin may also be a photoresist. Either a positive-type material or a negative-type material may be used as the photosensitive resin.

[0575] The insulating layer 127 may be made of a material that absorbs visible light. The insulating layer 127 absorbs light emitted from the light-emitting element, thereby suppressing leakage of light from the light-emitting element to an adjacent light-emitting element through the insulating layer 127 (stray light). This can improve the display quality of the display device. Furthermore, since the display quality can be improved without using a polarizing plate in the display device, the display device can be made lighter and thinner.

[0576] Examples of materials that absorb visible light include materials containing pigments such as black, materials containing dyes, light-absorbing resin materials (e.g., polyimide), and resin materials that can be used for color filters (color filter materials). In particular, using a resin material in which two or more color filter materials are laminated or mixed is preferable because it can enhance the visible light blocking effect. In particular, mixing three or more color filter materials makes it possible to form a black or nearly black resin layer.

[0577] [Display Device 50F] Figure 24B shows an example of a cross section of the display unit 162 of the display device 50F. The display device 50F differs from the display device 50E mainly in that a light-emitting element having a layer 133 and a colored layer (such as a color filter) are used in each subpixel of each color. The configuration shown in Figure 24B can be combined with the region including the FPC 172, the circuit portion 164, the stacked structure from the substrate 151 to the insulating layer 235 of the display unit 162, the connection portion 140, and the configuration of the end portion shown in Figure 24A.

[0578] A display device 50F shown in FIG. 24B includes light emitting elements 130R, 130G, and 130B, a colored layer 132R that transmits red light, a colored layer 132G that transmits green light, and a colored layer 132B that transmits blue light.

[0579] The light emitted from the light emitting element 130R is extracted as red light to the outside of the display device 50F via the colored layer 132R. Similarly, the light emitted from the light emitting element 130G is extracted as green light to the outside of the display device 50F via the colored layer 132G. The light emitted from the light emitting element 130B is extracted as blue light to the outside of the display device 50F via the colored layer 132B.

[0580] Each of the light-emitting elements 130R, 130G, and 130B has a layer 133. These three layers 133 are formed using the same process and the same material. Furthermore, these three layers 133 are spaced apart from one another. By providing an island-shaped EL layer for each light-emitting element, leakage current between adjacent light-emitting elements can be suppressed. This makes it possible to prevent unintended light emission due to crosstalk, and realize a display device with extremely high contrast.

[0581] 24B emit white light. The white light emitted by the light emitting elements 130R, 130G, and 130B passes through the colored layers 132R, 132G, and 132B, thereby obtaining light of a desired color.

[0582] Alternatively, for example, the light-emitting elements 130R, 130G, and 130B shown in FIG. 24B emit blue light. In this case, the layer 133 includes one or more light-emitting layers that emit blue light. In the sub-pixel 11B that emits blue light, the blue light emitted by the light-emitting element 130B can be extracted. Furthermore, in the sub-pixel 11R that emits red light and the sub-pixel 11G that emits green light, a color conversion layer can be provided between the light-emitting element 130R or the light-emitting element 130G and the substrate 152 to convert the blue light emitted by the light-emitting element 130R or the light-emitting element 130G into light with a longer wavelength, thereby allowing red or green light to be extracted. Furthermore, it is preferable to provide a coloring layer 132R between the color conversion layer and the substrate 152 on the light-emitting element 130R, and a coloring layer 132G between the color conversion layer and the substrate 152 on the light-emitting element 130G. By extracting the light transmitted through the color conversion layer via the colored layer, light other than the desired color can be absorbed by the colored layer, thereby increasing the color purity of the light emitted by the sub-pixel.

[0583] [Display Device 50G] A display device 50G shown in FIG. 25 differs from the display device 50F mainly in that it is a bottom-emission display device.

[0584] Light emitted from the light-emitting element is emitted toward the substrate 151. A material that is highly transparent to visible light is preferably used for the substrate 151. On the other hand, the light-transmitting property of a material used for the substrate 152 does not matter.

[0585] 25 shows an example in which the light-shielding layer 117 is provided over the substrate 151, the insulating layer 153 is provided over the light-shielding layer 117, and the transistors 205D, 205R (not shown), 205G, and 205B are provided over the insulating layer 153. In addition, the coloring layers 132R, 132G, and 132B are provided over the insulating layer 218, and the insulating layer 235 is provided over the coloring layers 132R, 132G, and 132B.

[0586] The light emitting element 130R overlapping the colored layer 132R includes a conductive layer 124R, a conductive layer 126R, a layer 133, a common layer 114, and a common electrode 115.

[0587] The light emitting element 130G overlapping the colored layer 132G includes a conductive layer 124G, a conductive layer 126G, a layer 133, a common layer 114, and a common electrode 115.

[0588] The light emitting element 130B overlapping the colored layer 132B has a conductive layer 124B, a conductive layer 126B, a layer 133, a common layer 114, and a common electrode 115.

[0589] The conductive layers 124R, 124G, 124B, 126R, 126G, and 126B are each made of a material that is highly transparent to visible light. It is preferable to use a material that reflects visible light for the common electrode 115. In a bottom-emission display device, a low-resistance metal or the like can be used for the common electrode 115, which can suppress voltage drops caused by the resistance of the common electrode 115 and achieve high display quality.

[0590] The transistor of one embodiment of the present invention can be miniaturized and its occupation area can be reduced; therefore, in a bottom-emission display device, the aperture ratio of a pixel can be increased or the pixel size can be reduced.

[0591] [Display Device 50H] A display device 50H shown in FIG. 26 is a VA mode liquid crystal display device.

[0592] Substrate 151 and substrate 152 are bonded together by adhesive layer 144. Liquid crystal 262 is sealed in the area surrounded by substrate 151, substrate 152, and adhesive layer 144. Polarizing plate 260a is located on the outer surface of substrate 152, and polarizing plate 260b is located on the outer surface of substrate 151. Although not shown, a backlight can be provided outside polarizing plate 260a or polarizing plate 260b.

[0593] Transistors 205D, 205R, and 205G, a connection portion 204, a spacer 224, and the like are provided on the substrate 151. The transistor 205D is provided in the circuit portion 164, and the transistors 205R and 205G are provided in the display portion 162. The conductive layers 112b of the transistors 205R and 205G function as pixel electrodes of the liquid crystal element 60.

[0594] The substrate 152 is provided with colored layers 132R and 132G, a light-shielding layer 117, an insulating layer 225, a conductive layer 263, etc. The conductive layer 263 functions as a common electrode for the liquid crystal element 60.

[0595] The transistors 205D, 205R, and 205G each include a conductive layer 112a, a semiconductor layer 108, an insulating layer 106, a conductive layer 104, and a conductive layer 112b. The conductive layer 112a functions as one of a source electrode and a drain electrode, and the conductive layer 112b functions as the other of the source electrode and the drain electrode. The conductive layer 104 functions as a gate electrode. A part of the insulating layer 106 functions as a gate insulating layer.

[0596] A conductive layer 103 is provided on and in contact with the conductive layer 112a. The conductive layer 103 contains a conductive material having higher conductivity than the conductive layer 112a and functions as an auxiliary wiring. The conductive layer 103 is in contact with part of the semiconductor layer 108.

[0597] As described above, in this embodiment, OS transistors are used as the transistors 205D, 205R, and 205G. The transistors 205D, 205R, and 205G can be transistors of one embodiment of the present invention. That is, the display device 50H includes transistors of one embodiment of the present invention in both the display portion 162 and the circuit portion 164. By using the transistor of one embodiment of the present invention in the display portion 162, the pixel size can be reduced, leading to higher resolution. Furthermore, by using the transistor of one embodiment of the present invention in the circuit portion 164, the area occupied by the circuit portion 164 can be reduced, leading to a narrower frame. The description of the previous embodiment can be referred to for the transistor of one embodiment of the present invention.

[0598] The transistors 205D, 205R, and 205G are covered with an insulating layer 218. The insulating layer 218 functions as a protective layer for the transistors 205D, 205R, and 205G.

[0599] Each subpixel included in the display unit 162 includes a transistor, a liquid crystal element 60, and a colored layer. For example, a subpixel that emits red light includes a transistor 205R, a liquid crystal element 60, and a colored layer 132R that transmits red light. A subpixel that emits green light includes a transistor 205G, a liquid crystal element 60, and a colored layer 132G that transmits green light. Although not shown, a subpixel that emits blue light similarly includes a transistor, a liquid crystal element 60, and a colored layer that transmits blue light.

[0600] The liquid crystal element 60 includes a conductive layer 112b, a conductive layer 263, and a liquid crystal 262 sandwiched between them.

[0601] Furthermore, a conductive layer 264 is provided on the substrate 151 and is located on the same plane as the conductive layer 112a. The conductive layer 264 has a portion that overlaps with the conductive layer 112b via the insulating layer 110 (insulating layer 110a, insulating layer 110b, and insulating layer 110c). A storage capacitor is formed by the conductive layer 112b, the conductive layer 264, and the insulating layer 110 therebetween. Note that it is sufficient that there be one or more insulating layers between the conductive layer 112b and the conductive layer 264, and one or two of the insulating layers 110 may be removed by etching.

[0602] On the substrate 152 side, an insulating layer 225 is provided to cover the colored layers 132R and 132G and the light-shielding layer 117. The insulating layer 225 may also function as a planarizing film. The insulating layer 225 can make the surface of the conductive layer 263 approximately flat, thereby making the alignment state of the liquid crystal 262 uniform.

[0603] Note that an alignment film for controlling the alignment of the liquid crystal 262 may be provided on the surfaces of the conductive layer 263, the insulating layer 218, etc. that come into contact with the liquid crystal 262 (see the alignment film 265 in Figures 28A and 28B).

[0604] The conductive layer 112b and the conductive layer 263 transmit visible light. In other words, the display device 50H can be a transmissive liquid crystal display device. For example, if a backlight is disposed on the substrate 152 side, light from the backlight polarized by the polarizing plate 260a passes through the substrate 152, the conductive layer 263, the liquid crystal 262, the conductive layer 112b, and the substrate 151 before reaching the polarizing plate 260b. At this time, the orientation of the liquid crystal 262 can be controlled by applying a voltage between the conductive layer 112b and the conductive layer 263, thereby controlling the optical modulation of the light. In other words, the intensity of the light emitted via the polarizing plate 260b can be controlled. Furthermore, the colored layer absorbs light outside a specific wavelength range of the incident light, so that the extracted light exhibits, for example, red light.

[0605] Here, a linear polarizer may be used as the polarizer 260b, but a circular polarizer can also be used. For example, a circular polarizer may be a laminate of a linear polarizer and a quarter-wave retardation plate. By using a circular polarizer as the polarizer 260b, it is possible to suppress reflection of external light.

[0606] When a circular polarizer is used as polarizer 260b, a circular polarizer or a normal linear polarizer may also be used as polarizer 260a. The desired contrast can be achieved by adjusting the cell gap, orientation, drive voltage, etc. of the liquid crystal element used in liquid crystal element 60 depending on the type of polarizer used for polarizers 260a and 260b.

[0607] The conductive layer 263 is electrically connected to a conductive layer 166b provided on the substrate 151 side by a connector 223 in the connection portion 140. The conductive layer 166b is connected to the conductive layer 165b through an opening provided in the insulating layer 110. This allows a potential or a signal to be supplied to the conductive layer 263 from an FPC or an IC arranged on the substrate 151 side. In the structure shown in Figure 26, the conductive layer 165b is formed from the same material and in the same process as the conductive layer 112a and the conductive layer 103, and the conductive layer 166b is formed from the same material and in the same process as the conductive layer 112b.

[0608] The connectors 223 can be, for example, conductive particles. Examples of conductive particles include particles of resin or silica coated with a metal material. Nickel or gold is preferable as the metal material because it reduces contact resistance. It is also preferable to use particles coated with two or more layers of metal materials, such as nickel coated with gold. It is also preferable to use a material that undergoes elastic or plastic deformation as the connectors 223. In this case, the conductive particles may be crushed vertically, as shown in FIG. 26 . This increases the contact area between the connectors 223 and the conductive layer electrically connected to them, thereby reducing contact resistance and preventing problems such as poor connection. The connectors 223 are preferably arranged so that they are covered by the adhesive layer 144. For example, it is preferable to disperse the connectors 223 in the adhesive layer 144 before curing.

[0609] A connection portion 204 is provided in a region near the end of the substrate 151. In the connection portion 204, the conductive layer 166a is electrically connected to the FPC 172 through a connection layer 242. The conductive layer 166a is connected to the conductive layer 165a through an opening provided in the insulating layer 110. In the structure shown in FIG. 26 , the conductive layer 165a is formed from the same material and in the same process as the conductive layer 112a and the conductive layer 103, and the conductive layer 166a is formed from the same material and in the same process as the conductive layer 112b.

[0610] 27 is an FFS mode liquid crystal display device. The display device 50I differs from the display device 50H mainly in the configuration of the liquid crystal element 60.

[0611] A conductive layer 263 functioning as a common electrode of the liquid crystal element 60 is provided over the insulating layer 110, and an insulating layer 261 is provided over the conductive layer 263. In addition, a conductive layer 112b functioning as the other of the source electrode and drain electrode of the transistor and as a pixel electrode of the liquid crystal element 60 is provided over the insulating layer 261. An insulating layer 218 is provided over the conductive layer 112b.

[0612] The conductive layer 112b has a comb-like shape or a shape provided with slits in a plan view. The conductive layer 263 is disposed to overlap with the conductive layer 112b. In addition, in a region overlapping with the colored layer, there is a portion on the conductive layer 263 where the conductive layer 112b is not disposed.

[0613] A capacitance is formed by stacking the conductive layer 112b and the conductive layer 263 with the insulating layer 261 interposed therebetween. Therefore, there is no need to separately form a capacitor element, and the aperture ratio of the pixel can be increased.

[0614] In the liquid crystal element 60, both the conductive layer 112b and the conductive layer 263 may have a comb-like top surface. On the other hand, as shown in a display device 50I, in the liquid crystal element 60, by forming only one of the conductive layer 112b and the conductive layer 263 into a comb-like top surface, the conductive layer 112b and the conductive layer 263 partially overlap with each other. This allows the capacitance between the conductive layer 112b and the conductive layer 263 to be used as a storage capacitor, eliminating the need for a separate capacitor, and enabling the aperture ratio of the display device to be increased.

[0615] 28A , the portion of the insulating layer 110b that overlaps with the liquid crystal element 60 is removed by etching. The liquid crystal element 60 of the display device 50J has a portion where a conductive layer 112c, an insulating layer 110a, an insulating layer 110c, and a conductive layer 112b are stacked in this order. By not overlapping the liquid crystal element 60 with the insulating layer 110b, not only can the light transmittance be increased, but the number of interfaces located on the path of light from the light source can also be reduced, thereby suppressing the effects of interface reflection and interface scattering.

[0616] The conductive layer 112b functions as a pixel electrode of the liquid crystal element 60. The conductive layer 112c functions as a common electrode of the liquid crystal element 60. The conductive layer 112c is formed using the same conductive film as the conductive layer 112a.

[0617] Note that a portion of either or both of the insulating layers 106 and 218 that overlaps with the liquid crystal element 60 may be removed by etching. Alternatively, the insulating layer 218 may not be provided. This allows the electric field of the conductive layers 112b and 112c to be easily transmitted to the liquid crystal 262, thereby enabling high-speed operation of the liquid crystal element 60. Furthermore, not only is the light transmittance in the portion overlapping with the liquid crystal element 60 increased, but the effects of interface reflection and interface scattering can also be suppressed. Furthermore, a portion of either the insulating layer 110a and 110c that overlaps with the liquid crystal element 60 may be removed by etching. This also allows the electric field of the conductive layers 112b and 112c to be easily transmitted to the liquid crystal 262. Furthermore, the capacitance between the conductive layers 112b and 112c can be increased in some cases.

[0618] In the liquid crystal element 60, both the conductive layer 112b and the conductive layer 112c may have a comb-like top surface. On the other hand, as shown in a display device 50J, in the liquid crystal element 60, by forming only one of the conductive layer 112b and the conductive layer 112c into a comb-like top surface, the conductive layer 112b and the conductive layer 112c partially overlap with each other. This allows the capacitance between the conductive layer 112b and the conductive layer 112c to be used as a storage capacitor, eliminating the need for a separate capacitor element and increasing the aperture ratio of the display device.

[0619] 28B differs from the display device 50I in that a common electrode is provided over a pixel electrode. The conductive layer 112b of the transistor 100 functions as a pixel electrode in the liquid crystal element 60. The insulating layer 106 and the insulating layer 218 are provided over the conductive layer 112b, and a conductive layer 263 is provided over the insulating layer 218. The conductive layer 263 functions as a common electrode in the liquid crystal element 60. The conductive layer 263 has a comb-like shape or a shape provided with slits in a plan view.

[0620] [Example of a Method for Manufacturing a Display Device] A method for manufacturing a display device using an MML (metal maskless) structure will be described below with reference to Fig. 29. Here, a process for manufacturing light-emitting elements without using a fine metal mask will be described in detail. Fig. 29 shows cross-sectional views of three light-emitting elements and a connection portion 140 included in a display unit 162 at each step.

[0621] The light-emitting element can be fabricated using vacuum processes such as vapor deposition, and solution processes such as spin coating and inkjet printing. Vapor deposition methods include physical vapor deposition (PVD) methods such as sputtering, ion plating, ion beam deposition, molecular beam deposition, and vacuum deposition, and chemical vapor deposition (CVD). In particular, functional layers included in the EL layer (hole injection layer, hole transport layer, hole blocking layer, light-emitting layer, electron blocking layer, electron transport layer, electron injection layer, charge generation layer, etc.) can be formed by vapor deposition (vacuum deposition, etc.), coating methods (dip coating, die coating, bar coating, spin coating, spray coating, etc.), printing methods (inkjet printing, screen (stencil printing), offset (lithographic printing), flexography (relief printing), gravure printing, microcontact printing, etc.), etc.

[0622] The island-shaped layer (layer including the light-emitting layer) manufactured by the manufacturing method of the display device described below is not formed using a fine metal mask, but is formed by forming the light-emitting layer on the entire surface and then processing it using photolithography. Therefore, it is possible to realize a high-definition display device or a display device with a high aperture ratio, which has been difficult to achieve until now. Furthermore, since the light-emitting layer can be made separately for each color, it is possible to realize a display device that is extremely vivid, has high contrast, and has high display quality. Furthermore, by providing a sacrificial layer on the light-emitting layer, damage to the light-emitting layer during the manufacturing process of the display device can be reduced, thereby improving the reliability of the light-emitting element.

[0623] For example, if a display device is composed of three types of light-emitting elements, namely, a light-emitting element that emits blue light, a light-emitting element that emits green light, and a light-emitting element that emits red light, three types of island-shaped light-emitting layers can be formed by repeating the deposition of the light-emitting layer and processing by photolithography three times.

[0624] First, the pixel electrodes 111R, 111G, and 111B and the conductive layer 123 are formed on the substrate 151 on which the transistors 205R, 205G, and 205B (not shown) are provided (FIG. 29A).

[0625] The conductive film to be the pixel electrodes can be formed by, for example, sputtering or vacuum evaporation. After a resist mask is formed on the conductive film by a photolithography process, the conductive film is processed to form the pixel electrodes 111R, 111G, and 111B and the conductive layer 123. The conductive film can be processed by either or both of a wet etching method and a dry etching method.

[0626] Next, a film 133Bf, which will later become the layer 133B, is formed on the pixel electrodes 111R, 111G, and 111B (FIG. 29A). The film 133Bf (later layer 133B) includes a light-emitting layer that emits blue light.

[0627] In this embodiment mode, an example is shown in which an island-shaped EL layer included in a light-emitting element that emits blue light is first formed, and then an island-shaped EL layer included in a light-emitting element that emits light of another color is formed.

[0628] In the process of forming the island-shaped EL layer, the pixel electrodes of the light-emitting elements of the colors formed second or later may be damaged in the previous process, which may result in a higher driving voltage for the light-emitting elements of the colors formed second or later.

[0629] Therefore, when manufacturing a display device according to one embodiment of the present invention, it is preferable to start with an island-shaped EL layer of a light-emitting element that emits light with the shortest wavelength (for example, a blue light-emitting element). For example, it is preferable to form the island-shaped EL layers in the order of blue, green, and red, or blue, red, and green.

[0630] This maintains a good state of the interface between the pixel electrode and the EL layer in the blue light-emitting element, and prevents the drive voltage of the blue light-emitting element from increasing. It also extends the life of the blue light-emitting element and improves its reliability. Since the red and green light-emitting elements are less susceptible to increases in drive voltage, etc., compared to the blue light-emitting element, the drive voltage of the entire display device can be reduced and reliability can be improved.

[0631] The order of forming the island-shaped EL layers is not limited to the above, and may be, for example, red, green, and blue.

[0632] 29A , the film 133Bf is not formed on the conductive layer 123. For example, by using an area mask, the film 133Bf can be formed only in a desired region. By employing a film formation process using an area mask and a processing process using a resist mask, the light-emitting element can be fabricated by a relatively simple process.

[0633] The heat resistance temperature of the compounds contained in the film 133Bf is preferably 100° C. or higher and 180° C. or lower, more preferably 120° C. or higher and 180° C. or lower, and more preferably 140° C. or higher and 180° C. or lower. This can improve the reliability of the light-emitting element. Also, the upper limit of the temperature allowable in the manufacturing process of the display device can be increased. Therefore, the range of choices for materials and manufacturing methods used in the display device can be expanded, and the yield and reliability can be improved.

[0634] The heat resistance temperature can be, for example, any one of the glass transition point, softening point, melting point, thermal decomposition temperature, and 5% weight loss temperature, preferably the lowest temperature among these.

[0635] The film 133Bf can be formed by, for example, a vapor deposition method, specifically a vacuum deposition method. Alternatively, the film 133Bf may be formed by a transfer method, a printing method, an inkjet method, a coating method, or the like.

[0636] Subsequently, a sacrificial layer 118B is formed on the film 133Bf and the conductive layer 123 ( FIG. 29A ). After a resist mask is formed by a photolithography process on the film that will become the sacrificial layer 118B, the film is processed to form the sacrificial layer 118B.

[0637] By providing the sacrificial layer 118B over the film 133Bf, damage to the film 133Bf during the manufacturing process of the display device can be reduced, and the reliability of the light-emitting element can be improved.

[0638] The sacrificial layer 118B is preferably provided so as to cover the respective ends of the pixel electrodes 111R, 111G, and 111B. This means that the ends of the layer 133B, which will be formed in a later process, will be located outside the ends of the pixel electrode 111B. This allows the entire upper surface of the pixel electrode 111B to be used as a light-emitting region, thereby increasing the aperture ratio of the pixel. Furthermore, since the ends of the layer 133B may be damaged in a process after the formation of the layer 133B, it is preferable that they be located outside the ends of the pixel electrode 111B, i.e., not be used as a light-emitting region. This makes it possible to suppress variations in the characteristics of the light-emitting elements and improve reliability.

[0639] Furthermore, since the layer 133B covers the top and side surfaces of the pixel electrode 111B, each step after the formation of the layer 133B can be performed without exposing the pixel electrode 111B. If the edge of the pixel electrode 111B is exposed, corrosion may occur during an etching step or the like. By suppressing corrosion of the pixel electrode 111B, the yield and characteristics of the light-emitting element can be improved.

[0640] In addition, the sacrificial layer 118B is preferably provided also in a position overlapping with the conductive layer 123. This can prevent the conductive layer 123 from being damaged during the manufacturing process of the display device.

[0641] The sacrificial layer 118B is made of a film that is highly resistant to the processing conditions of the film 133Bf, specifically, a film that has a large etching selectivity with respect to the film 133Bf.

[0642] The sacrificial layer 118B is formed at a temperature lower than the heat resistance temperature of each compound contained in the film 133Bf. The substrate temperature when forming the sacrificial layer 118B is typically 200° C. or lower, preferably 150° C. or lower, more preferably 120° C. or lower, more preferably 100° C. or lower, and even more preferably 80° C. or lower.

[0643] A high heat resistance temperature of the compound contained in the film 133Bf is preferable because the film formation temperature of the sacrificial layer 118B can be increased. For example, the substrate temperature during the formation of the sacrificial layer 118B can be set to 100°C or higher, 120°C or higher, or 140°C or higher. The higher the film formation temperature, the denser the inorganic insulating film can be and the higher the barrier properties can be. Therefore, by forming the sacrificial layer at such a temperature, damage to the film 133Bf can be further reduced, and the reliability of the light-emitting element can be improved.

[0644] The same applies to the film formation temperatures of other layers (for example, the insulating film 125f) formed on the film 133Bf.

[0645] The sacrificial layer 118B can be formed by, for example, sputtering, ALD (including thermal ALD and PEALD), CVD, or vacuum deposition. Alternatively, the sacrificial layer 118B may be formed by the wet film formation method described above.

[0646] The sacrificial layer 118B (a layer provided in contact with the film 133Bf when the sacrificial layer 118B has a laminated structure) is preferably formed using a formation method that causes less damage to the film 133Bf. For example, it is preferable to use the ALD method or the vacuum deposition method rather than the sputtering method.

[0647] The sacrificial layer 118B can be processed by wet etching or dry etching, and is preferably processed by anisotropic etching.

[0648] By using the wet etching method, damage to the film 133Bf during processing of the sacrificial layer 118B can be reduced compared to when using the dry etching method. When using the wet etching method, it is preferable to use, for example, a developer, a tetramethylammonium hydroxide (TMAH) aqueous solution, dilute hydrofluoric acid, oxalic acid, phosphoric acid, acetic acid, nitric acid, or a mixed solution containing two or more of these. Furthermore, when using the wet etching method, a mixed acid chemical solution containing water, phosphoric acid, dilute hydrofluoric acid, and nitric acid may also be used. Note that the chemical solution used in the wet etching process may be alkaline or acidic.

[0649] The sacrificial layer 118B may be made of one or more of a metal film, an alloy film, a metal oxide film, a semiconductor film, an inorganic insulating film, and an organic insulating film, for example.

[0650] The sacrificial layer 118B can be made of a metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, titanium, aluminum, yttrium, zirconium, and tantalum, or an alloy material containing such a metal material.

[0651] The sacrificial layer 118B can be made of a metal oxide such as In-Ga-Zn oxide, indium oxide, In-Zn oxide, In-Sn oxide, indium titanium oxide (In-Ti oxide), indium tin zinc oxide (In-Sn-Zn oxide), indium titanium zinc oxide (In-Ti-Zn oxide), indium gallium tin zinc oxide (In-Ga-Sn-Zn oxide), or indium tin oxide containing silicon.

[0652] In addition, instead of the above gallium, an element M (M is one or more elements selected from aluminum, silicon, boron, yttrium, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium) may be used.

[0653] For example, semiconductor materials such as silicon or germanium can be used as materials that are highly compatible with semiconductor manufacturing processes. Alternatively, oxides or nitrides of the above semiconductor materials can be used. Alternatively, non-metallic materials such as carbon or compounds thereof can be used. Alternatively, metals such as titanium, tantalum, tungsten, chromium, and aluminum, or alloys containing one or more of these, can be used. Alternatively, oxides containing the above metals, such as titanium oxide or chromium oxide, or nitrides such as titanium nitride, chromium nitride, or tantalum nitride can be used.

[0654] Furthermore, various inorganic insulating films that can be used for the protective layer 131 can be used for the sacrificial layer 118B. In particular, oxide insulating films are preferable because they have higher adhesion to the film 133Bf than nitride insulating films. For example, inorganic insulating materials such as aluminum oxide, hafnium oxide, and silicon oxide can be used for the sacrificial layer 118B. For example, an aluminum oxide film can be formed as the sacrificial layer 118B using the ALD method. Using the ALD method is preferable because it can reduce damage to the base (particularly the film 133Bf).

[0655] For example, the sacrificial layer 118B can be a stacked structure of an inorganic insulating film (e.g., an aluminum oxide film) formed using the ALD method and an inorganic film (e.g., an In-Ga-Zn oxide film, a silicon film, or a tungsten film) formed using the sputtering method.

[0656] The same inorganic insulating film can be used for both the sacrificial layer 118B and the insulating layer 125 to be formed later. For example, an aluminum oxide film formed using an ALD method can be used for both the sacrificial layer 118B and the insulating layer 125. The same deposition conditions can be applied to the sacrificial layer 118B and the insulating layer 125, or different deposition conditions can be applied. For example, by depositing the sacrificial layer 118B under the same conditions as the insulating layer 125, the sacrificial layer 118B can be an insulating layer with high barrier properties against at least one of water and oxygen. On the other hand, since the sacrificial layer 118B is a layer that is removed mostly or entirely in a later process, it is preferable that it be easily processed. Therefore, the sacrificial layer 118B is preferably deposited under conditions where the substrate temperature during deposition is lower than that of the insulating layer 125.

[0657] An organic material may be used for the sacrificial layer 118B. For example, the organic material may be a material that is soluble in a solvent that is chemically stable with respect to at least the film located at the top of the film 133Bf. In particular, a material that dissolves in water or alcohol is preferably used. When forming a film of such a material, it is preferable to apply the material dissolved in a solvent such as water or alcohol using a wet film formation method, and then perform a heat treatment to evaporate the solvent. In this case, performing the heat treatment under a reduced pressure atmosphere is preferable because it allows the solvent to be removed at a low temperature and in a short time, thereby reducing thermal damage to the film 133Bf.

[0658] The sacrificial layer 118B may be made of a resin such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, alcohol-soluble polyamide resin, or a fluororesin such as a perfluoropolymer.

[0659] For example, the sacrificial layer 118B can be a laminated structure of an organic film (e.g., a PVA film) formed using either a vapor deposition method or the above-mentioned wet film formation method, and an inorganic film (e.g., a silicon nitride film) formed using a sputtering method.

[0660] Note that in the display device of one embodiment of the present invention, part of the sacrificial film may remain as a sacrificial layer.

[0661] Subsequently, the film 133Bf is processed using the sacrificial layer 118B as a hard mask to form a layer 133B (FIG. 29B).

[0662] 29B , a stacked structure of the layer 133B and the sacrificial layer 118B remains on the pixel electrode 111B. The pixel electrodes 111R and 111G are exposed. In addition, the sacrificial layer 118B remains on the conductive layer 123 in the region corresponding to the connection portion 140.

[0663] The film 133Bf is preferably processed by anisotropic etching, particularly anisotropic dry etching, or wet etching.

[0664] Thereafter, the steps of forming the film 133Bf, the step of forming the sacrificial layer 118B, and the step of forming the layer 133B are repeated at least twice, changing the light-emitting material, to form a layered structure of the layer 133R and the sacrificial layer 118R on the pixel electrode 111R, and a layered structure of the layer 133G and the sacrificial layer 118G on the pixel electrode 111G ( FIG. 29C ). Specifically, the layer 133R is formed to include a light-emitting layer that emits red light, and the layer 133G is formed to include a light-emitting layer that emits green light. The sacrificial layers 118R and 118G can be made of the same material as that used for the sacrificial layer 118B, and may be made of the same material or different materials.

[0665] The side surfaces of the layers 133B, 133G, and 133R are preferably perpendicular or substantially perpendicular to the surface on which they are to be formed. For example, the angle between the surface on which they are to be formed and these side surfaces is preferably 60 degrees or more and 90 degrees or less.

[0666] As described above, the distance between any two adjacent layers of the layers 133B, 133G, and 133R formed using photolithography can be narrowed to 8 μm or less, 5 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less. Here, the distance can be defined, for example, as the distance between the opposing ends of any two adjacent layers of the layers 133B, 133G, and 133R. By narrowing the distance between the island-shaped EL layers in this manner, a display device with high definition and a large aperture ratio can be provided.

[0667] Next, an insulating film 125f, which will later become the insulating layer 125, is formed to cover the pixel electrode, layer 133B, layer 133G, layer 133R, sacrificial layer 118B, sacrificial layer 118G, and sacrificial layer 118R, and an insulating layer 127 is formed on the insulating film 125f (Figure 29D).

[0668] The insulating film 125f is preferably formed to a thickness of 3 nm or more, 5 nm or more, or 10 nm or more, and 200 nm or less, 150 nm or less, 100 nm or less, or 50 nm or less.

[0669] The insulating film 125f is preferably formed by, for example, an ALD method. The ALD method is preferable because it can reduce film formation damage and form a film with high coverage. The insulating film 125f is preferably formed as an aluminum oxide film by, for example, an ALD method.

[0670] Alternatively, the insulating film 125f may be formed by a sputtering method, a CVD method, or a PECVD method, which have a faster film formation rate than an ALD method. This enables a highly reliable display device to be manufactured with high productivity.

[0671] The insulating film that becomes the insulating layer 127 is preferably formed by the aforementioned wet film formation method (e.g., spin coating) using, for example, a photosensitive resin composition containing an acrylic resin. After film formation, it is preferable to perform a heat treatment (also called pre-baking) to remove the solvent contained in the insulating film. Next, visible light or ultraviolet light is irradiated onto a portion of the insulating film to expose the portion. Next, development is performed to remove the exposed region of the insulating film. Next, a heat treatment (also called post-baking) is performed. This allows the insulating layer 127 shown in FIG. 29D to be formed. Note that the shape of the insulating layer 127 is not limited to the shape shown in FIG. 29D. For example, the top surface of the insulating layer 127 can have one or more of a convex curved surface, a concave curved surface, and a flat surface. Furthermore, the insulating layer 127 may cover the side surfaces of the end portions of at least one of the insulating layer 125, the sacrificial layer 118B, the sacrificial layer 118G, and the sacrificial layer 118R.

[0672] 29E , an etching process is performed using the insulating layer 127 as a mask to remove the insulating film 125f and portions of the sacrificial layers 118B, 118G, and 118R. As a result, openings are formed in the sacrificial layers 118B, 118G, and 118R, respectively, exposing the top surfaces of the layers 133B, 133G, and 133R, and the conductive layer 123. Note that portions of the sacrificial layers 118B, 118G, and 118R may remain in positions overlapping with the insulating layer 127 and the insulating layer 125 (see sacrificial layers 119B, 119G, and 119R).

[0673] The etching process can be performed by dry etching or wet etching. Note that if the insulating film 125f is formed using the same material as the sacrificial layers 118B, 118G, and 118R, the etching process can be performed all at once, which is preferable.

[0674] As described above, by providing the insulating layer 127, the insulating layer 125, the sacrificial layer 118B, the sacrificial layer 118G, and the sacrificial layer 118R, it is possible to prevent poor connection between the light-emitting elements in the common layer 114 and the common electrode 115 due to separation and to prevent an increase in electrical resistance due to a locally thin portion of the film thickness. As a result, the display device of one embodiment of the present invention can have improved display quality.

[0675] Subsequently, the common layer 114 and the common electrode 115 are formed in this order on the insulating layer 127, the layer 133B, the layer 133G, and the layer 133R (FIG. 29F).

[0676] The common layer 114 can be formed by a method such as a vapor deposition method (including a vacuum deposition method), a transfer method, a printing method, an inkjet method, or a coating method.

[0677] For example, sputtering or vacuum deposition can be used to form the common electrode 115. Alternatively, a film formed by deposition and a film formed by sputtering may be stacked.

[0678] As described above, in the manufacturing method of a display device according to one embodiment of the present invention, the island-shaped layers 133B, 133G, and 133R are formed by forming a film over the entire surface and then processing it, rather than by using a fine metal mask. This allows the island-shaped layers to be formed with uniform thicknesses. This makes it possible to realize a high-resolution display device or a display device with a high aperture ratio. Furthermore, even when the resolution or aperture ratio is high and the distance between subpixels is extremely short, the layers 133B, 133G, and 133R can be prevented from contacting each other in adjacent subpixels. Therefore, leakage current between subpixels can be suppressed. This prevents unintended light emission due to crosstalk, and a display device with extremely high contrast can be realized.

[0679] Furthermore, by providing the insulating layer 127 having a tapered edge between adjacent island-shaped EL layers, it is possible to suppress the occurrence of a step during the forma...

Claims

1. It comprises a semiconductor layer, a first conductive layer, a second conductive layer, a third conductive layer, a fourth conductive layer, a first insulating layer, and a second insulating layer. At least a portion of the second conductive layer is in contact with the upper surface of the first conductive layer, The first insulating layer is located on the second conductive layer, The third conductive layer is located on the first insulating layer, The semiconductor layer is in contact with the upper surface of the first conductive layer, the side surface of the second conductive layer, the third conductive layer, and the side surface of the first insulating layer. The second insulating layer is located on the semiconductor layer, A semiconductor device wherein the fourth conductive layer is located on the second insulating layer and overlaps the semiconductor layer via the second insulating layer.

2. It comprises a semiconductor layer, a first conductive layer, a second conductive layer, a third conductive layer, a fourth conductive layer, a first insulating layer, and a second insulating layer. The second conductive layer has a first opening that is in contact with the upper surface of the first conductive layer and reaches the first conductive layer. The first insulating layer is located on the second conductive layer and has a second opening that overlaps with the first opening. The third conductive layer is located on the first insulating layer and has a third opening that overlaps with the first opening and the second opening. The semiconductor layer is in contact with the upper surface of the first conductive layer through the first to third openings, and is in contact with the side surface of the second conductive layer at the first opening, the third conductive layer, and the side surface of the first insulating layer at the second opening, The second insulating layer is located on the semiconductor layer, A semiconductor device wherein the fourth conductive layer is located on the second insulating layer and overlaps the semiconductor layer via the second insulating layer.

3. In claim 1 or 2, A semiconductor device wherein the shortest distance from the upper surface of the first conductive layer to the upper surface of the second conductive layer is longer than the shortest distance from the upper surface of the first conductive layer to the lower surface of the fourth conductive layer.

4. In claim 1 or 2, A semiconductor device wherein the conductivity of the second conductive layer is higher than that of the first conductive layer.

5. In claim 1 or 2, The semiconductor layer is in contact with the upper and side surfaces of the third conductive layer, and is a semiconductor device.

6. In claim 1 or 2, The semiconductor device comprises a semiconductor layer having a metal oxide.

7. In claim 1 or 2, A metal oxide is present between the semiconductor layer and the second conductive layer. The aforementioned metal oxide includes the metal contained in the second conductive layer, wherein the semiconductor device is a semiconductor device.

8. It comprises a first metal oxide layer, a second metal oxide layer, a first conductive layer, a second conductive layer, a third conductive layer, a fourth conductive layer, a first insulating layer, and a second insulating layer. At least a portion of the second conductive layer is in contact with the upper surface of the first conductive layer, The first insulating layer is located on the second conductive layer, The third conductive layer is located on the first insulating layer, The first metal oxide layer is in contact with the upper surface of the first conductive layer, the side surface of the second metal oxide layer, the third conductive layer, and the side surface of the first insulating layer. The second metal oxide layer is in contact with the side surface of the second conductive layer, The second insulating layer is located on the first metal oxide layer, The fourth conductive layer is located on the second insulating layer and overlaps the first metal oxide layer via the second insulating layer. A semiconductor device wherein the second metal oxide layer and the second conductive layer have the same metal element.

9. A first conductive layer having the function of either the source electrode or the drain electrode of a transistor, A second conductive layer having a region in contact with the upper surface of the first conductive layer, A first insulating layer having a region located on the second conductive layer, A third conductive layer having a region located on the first insulating layer and functioning as the other of the source electrode or drain electrode of the transistor, A semiconductor layer having a region in contact with the upper surface of the first conductive layer, a region in contact with the side surface of the second conductive layer, a region in contact with the upper surface of the third conductive layer, a region in contact with the side surface of the third conductive layer, and a region in contact with the side surface of the first insulating layer, and having a channel formation region for the transistor, A second insulating layer having the function of a gate insulating layer for the transistor, A semiconductor device comprising: a fourth conductive layer having a region facing the semiconductor layer via the second insulating layer, and having the function of a gate electrode of the transistor.

10. A first conductive layer having the function of either the source electrode or the drain electrode of a transistor, A second conductive layer having a region in contact with the upper surface of the first conductive layer and a first opening reaching the first conductive layer, A first insulating layer having a region located on the second conductive layer and a second opening having a region overlapping with the first opening, A third conductive layer having a region located on the first insulating layer, a third opening having a region overlapping with the first opening and the second opening, and functioning as the other of the source electrode or drain electrode of the transistor, A semiconductor layer having regions located within the first opening, the second opening, and the third opening, and having a region in contact with the upper surface of the first conductive layer, a region in contact with the side surface of the second conductive layer, a region in contact with the upper surface of the third conductive layer, a region in contact with the side surface of the third conductive layer, and a region in contact with the side surface of the first insulating layer, and having a channel-forming region for the transistor, A second insulating layer having regions located within the first opening, the second opening, and the third opening, and functioning as a gate insulating layer for the transistor, A semiconductor device comprising: a fourth conductive layer having regions located within the first opening, the second opening, and the third opening, having regions facing the semiconductor layer via the second insulating layer, and having a function as the gate electrode of the transistor.

11. A first conductive layer having the function of either the source electrode or the drain electrode of a transistor, A second conductive layer having a region in contact with the upper surface of the first conductive layer, A first insulating layer having a region located on the second conductive layer, A third conductive layer having a region located on the first insulating layer and functioning as the other of the source electrode or drain electrode of the transistor, A first metal oxide layer having a region in contact with the upper surface of the first conductive layer, a region in contact with the upper surface of the third conductive layer, a region in contact with the side surface of the third conductive layer, and a region in contact with the side surface of the first insulating layer, and having a channel-forming region for the transistor, A second metal oxide layer having a region located between the side surface of the second conductive layer and the side surface of the first metal oxide layer, A second insulating layer having the function of a gate insulating layer for the transistor, The transistor has a fourth conductive layer having a region facing the first metal oxide layer via the second insulating layer, and having a function as the gate electrode of the transistor. A semiconductor device wherein the second metal oxide layer and the second conductive layer have the same metal element.