Indication device

Abstract

Provided is a small-size display device with a narrow frame. This display device in which drive circuits and a pixel circuit are stacked, has a laminate of first to third layers, wherein the drive circuit is provided in the first layer and the second layer, and the pixel circuit is provided in the third layer. The first layer has a transistor having silicon in a semiconductor layer, and the second layer and the third layer each have a transistor having a metal oxide in a semiconductor layer. Further, the channel length of the transistor in the second layer is shorter than that of the transistor in the third layer, and the structure is suited to high-speed operations of the circuits.

Description

Display devices and electronic devices

[0001] One embodiment of the present invention relates to a display device and an electronic device.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. Examples of the technical field of one embodiment of the present invention disclosed in this specification and the like include a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, an electronic device, a lighting device, an input device, an input / output device, a driving method thereof, or a manufacturing method thereof.

[0003] In this specification and the like, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics. A transistor, a semiconductor circuit, an arithmetic device, a memory device, and the like are examples of semiconductor devices. In addition, imaging devices, electro-optical devices, power generation devices (including thin-film solar cells, organic thin-film solar cells, and the like), and electronic devices may include semiconductor devices.

[0004] 2. Description of the Related Art Goggle-type or eyeglass-type devices have been developed as electronic devices for virtual reality (VR) or augmented reality (AR).

[0005] Representative examples of small display devices applicable to goggle-type or eyeglass-type devices include display devices equipped with liquid crystal elements, and display devices equipped with organic EL (Electro Luminescence) elements or light-emitting diodes (LEDs: Light Emitting Diodes).

[0006] A display device equipped with an organic EL element does not require a backlight, which is necessary in a liquid crystal display device, and therefore can realize a thin, lightweight, high-contrast, and low-power display device. For example, an example of a display device using an organic EL element is described in Patent Document 1.

[0007] Furthermore, in order to reduce the production cost and mounting area of ​​a driver IC provided in a display device, Patent Document 2 discloses a technique in which part of the circuitry constituting the source driver is formed on a glass substrate in the same manner as the pixel circuit.

[0008] JP 2002-324673 A JP 2019-20687 A

[0009] Electronic devices used in VR, AR, and the like are a type of wearable device, and it is preferable that they are small and lightweight to improve portability and wearability. Therefore, it is desirable that the components that make up the electronic devices are small while still fulfilling the necessary functions.

[0010] In order to reduce the size of a display device, it is necessary to increase the pixel density and narrow the area outside the display area (frame).

[0011] A display device has a driver circuit for driving the pixel circuits. The driver circuit is generally configured to be mounted on an IC chip, or to have a portion of the driver circuit monolithically formed on the same substrate as the pixel circuit. Both configurations utilize the frame area, which limits how narrow the frame can be.

[0012] To further narrow the frame, it is preferable to arrange the driver circuit and the display area so that they overlap. For example, by forming pixel circuits using transistors that can be formed as thin films on the silicon substrate on which the driver circuit is formed, the frame can be made extremely narrow. Furthermore, by forming part of the driver circuit using transistors that can be formed as thin films, the degree of freedom in the circuits to be provided on the silicon substrate can be increased.

[0013] Therefore, an object of one embodiment of the present invention is to provide a small-sized display device. Another object is to provide a display device with a narrow frame. Another object is to provide a display device that can operate at high speed. Another object is to provide a display device with low power consumption. Another object is to provide a high-performance display device. Another object is to provide a novel display device. Another object is to provide an electronic device including the display device. Another object is to provide an electronic device with low power consumption. Another object is to provide a novel electronic device.

[0014] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these can be extracted from the description of the specification, drawings, claims, etc.

[0015] One embodiment of the present invention is a display device having a stacked structure of a driver circuit and a pixel circuit. A transistor constituting part of an element of the driver circuit includes a metal oxide in a semiconductor layer and has a structure suitable for high-speed operation.

[0016] A first aspect of the present invention is a display device including a pixel circuit and a driver circuit having a region overlapping with the pixel circuit, the driver circuit including a first circuit and a second circuit, the second circuit having a region overlapping with the first circuit, the pixel circuit having a region overlapping with the second circuit, the first circuit including a first transistor having silicon in a channel formation region, the second circuit including a second transistor having metal oxide in a semiconductor layer, the pixel circuit including a third transistor having metal oxide in a semiconductor layer, and the second transistor being a transistor whose channel formation region is provided along a side surface of an insulating layer.

[0017] In a first aspect, the pixel element may have a first layer, a second layer, and a third layer, the second layer being provided between the first layer and the third layer, the pixel circuit being provided in the third layer, the first circuit being provided in the first layer, and the second circuit being provided in the second layer.

[0018] A second aspect of the present invention is a display device having a first layer, a second layer, and a third layer, the second layer being provided between the first layer and the third layer, a pixel circuit being provided in the third layer, a driver circuit for the pixel circuit being provided in the first layer and the second layer, a first circuit being an element of the driver circuit being provided in the first layer, and a second circuit being an element of the driver circuit being provided in the second layer, the first circuit having a first transistor having silicon in a channel formation region, the second circuit having a second transistor having metal oxide in a semiconductor layer, the pixel circuit having a third transistor having metal oxide in the semiconductor layer, and the second transistor being a transistor whose channel formation region is provided along a side surface of an insulating layer included in the second layer.

[0019] A third aspect of the present invention is a liquid crystal display device having a first layer, a second layer, and a third layer, the second layer being provided between the first layer and the third layer, the second layer and the third layer being provided with pixel circuits, the first layer and the second layer being provided with drive circuits for the pixel circuits, the first layer being provided with a first circuit which is an element of the drive circuit, the second layer being provided with a second circuit which is an element of the drive circuit and a first element of the pixel circuit, the third layer being provided with the second element of the pixel circuit, and the first circuit being a The display device includes a first transistor having silicon in a channel formation region, a second circuit having a second transistor having metal oxide in a semiconductor layer, a pixel circuit having a fourth transistor having metal oxide in a semiconductor layer as a first element and a third transistor having metal oxide in a semiconductor layer as a second element, and the second transistor and the fourth transistor are transistors whose channel formation regions are provided along side surfaces of an insulating layer included in the second layer.

[0020] In the third aspect, it is preferable that the drive transistor of the pixel circuit is formed of a third transistor, the selection transistor of the pixel circuit is formed of a fourth transistor, the third transistor has a first conductive layer functioning as a first gate electrode and a second conductive layer functioning as a second gate, the first conductive layer and the second conductive layer are electrically connected, and the second conductive layer is electrically connected to one of the source electrode or the drain electrode of the fourth transistor.

[0021] In the first to third aspects, in a stack in which a first conductive layer, an insulating layer, and a second conductive layer are stacked in that order, openings can be provided in the insulating layer and the second conductive layer so as to reach the first conductive layer.

[0022] A transistor having a channel formation region provided along a side surface of an insulating layer can have a semiconductor layer having a metal oxide provided so as to cover an opening, a second insulating layer provided over the semiconductor layer having a metal oxide and the second conductive layer so as to cover a recess resulting from the opening, and a third conductive layer provided over the second insulating layer so as to fill the recess resulting from the opening.

[0023] In the first to third aspects, the first circuit and the second circuit are elements of a source driver, and the second circuit may include a pass transistor logic circuit or a latch circuit.

[0024] In the first to third aspects, the drive circuit is provided in a rectangular region when viewed from above, and the drive circuit can drive a plurality of pixel circuits provided on the rectangular region. Furthermore, a plurality of rectangular regions can be arranged in a matrix.

[0025] In the first to third aspects, the pixel circuit preferably has an organic EL element.

[0026] Note that an electronic device including the above-described display device, a lens, and a diopter adjustment mechanism is also one embodiment of the present invention.

[0027] According to one embodiment of the present invention, a small-sized display device can be provided. Alternatively, a display device with a narrow frame can be provided. Alternatively, a display device capable of high-speed operation can be provided. Alternatively, a display device with low power consumption can be provided. Alternatively, a high-performance display device can be provided. Alternatively, a novel display device can be provided. Alternatively, an electronic device including the display device can be provided. Alternatively, an electronic device with low power consumption can be provided. Alternatively, a novel electronic device can be provided.

[0028] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these can be extracted from the description in the specification, drawings, claims, etc.

[0029] FIG. 1 is a diagram illustrating the configuration of a display device. FIGS. 2A to 2C are diagrams illustrating the configuration of a display device. FIG. 3 is a block diagram illustrating a display device. FIG. 4 is a circuit diagram of a voltage generation circuit and a pass transistor logic circuit. FIGS. 5A to 5C are circuit diagrams of a latch circuit. FIGS. 6A to 6D are circuit diagrams of a pixel circuit. FIGS. 7A and 7B are diagrams illustrating vertical transistors. FIGS. 8A to 8C are diagrams illustrating an example configuration of a display panel. FIGS. 9A and 9B are diagrams illustrating an example configuration of a display panel. FIGS. 10A to 10F are diagrams illustrating an example configuration of a pixel. FIGS. 11A and 11B are diagrams illustrating an example configuration of a display panel. FIG. 12 is a diagram illustrating an example configuration of a display panel. FIG. 13 is a diagram illustrating an example configuration of a display panel. FIG. 14 is a diagram illustrating an example configuration of a display panel. FIGS. 15A to 15F are diagrams illustrating an example configuration of a light-emitting device. FIGS. 16A to 16C are diagrams illustrating an example configuration of a light-emitting device. 17A to 17F are diagrams illustrating an electronic device.

[0030] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art will readily understand that various modifications in form and detail may be made 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. In the configuration of the invention described below, the same parts or parts having similar functions will be designated by the same reference numerals in different drawings, and repeated description thereof may be omitted. Hatching of the same elements constituting the drawings may be omitted or changed as appropriate in different drawings.

[0031] Furthermore, even if a circuit diagram shows a single element, that element may be configured as multiple elements as long as there is no functional problem. For example, multiple transistors operating as switches may be connected in series or parallel. Also, a capacitance element may be divided and placed in multiple locations.

[0032] Furthermore, one conductor may have multiple functions, such as wiring, electrode, and terminal, and in this specification, multiple names may be used for the same element. Also, even when elements are shown as being directly connected to each other on a circuit diagram, in reality, the elements may be connected via one or more conductors, and in this specification, such a configuration is also included in the category of direct connection.

[0033] Furthermore, in drawings illustrating a laminated structure, elements other than those of each layer may be included. In a configuration in which two layers are in contact with each other, an element disposed near the boundary between the layers is illustrated as an element of one layer for convenience, but it may also be an element of the other layer.

[0034] Embodiment 1 In this embodiment, a display device according to one embodiment of the present invention will be described.

[0035] One embodiment of the present invention is a narrow-frame display device in which a driver circuit and a pixel circuit are stacked. The driver circuit is provided in a first layer and a second layer, and the pixel circuit is provided in a third layer. The second layer is located between the first layer and the third layer. Note that part of the pixel circuit can also be provided in the second layer.

[0036] The first layer includes a transistor having silicon in a semiconductor layer, and the second and third layers include transistors having metal oxide in a semiconductor layer. The transistor in the second layer has a shorter channel length than the transistor in the third layer and has a structure suitable for high-speed circuit operation.

[0037] This structure allows a narrow frame and a small display device to be formed. Furthermore, since a part of the driver circuit can be provided in the second layer, the area occupied by the driver circuit in the first layer can be reduced. Therefore, circuits other than the driver circuit can be provided in the first layer, and the display device can have high performance.

[0038] Furthermore, since the driver circuits provided in the first and second layers are arranged overlapping the pixel circuits, the wiring length can be shortened. This allows for reduced wiring resistance and wiring capacitance, resulting in less signal delay and a display device with low power consumption. Furthermore, by dividing the driver circuits into multiple parts and operating them in parallel, high-speed operation of the display device is possible.

[0039] In addition, in a configuration in which the driver circuit is divided into multiple sections, the amount of data transmission can be reduced by varying the frame frequency and display resolution for each display area, thereby achieving high-speed operation and low power consumption. For example, the display near the line of sight can be displayed at a high resolution and a high frame frequency, and the display outside the line of sight can be displayed at a low resolution and a low frame frequency. This type of operation is also called foveal rendering.

[0040] FIG. 1 illustrates a display device according to one embodiment of the present invention. The display device 10 has a stacked structure including a layer 20, a layer 30a, and a layer 30b, and the layers are shown separated from each other in FIG. 1 . Note that the layers 30a and 30b may be referred to as the layer 30 without distinction. A wiring layer or the like may be provided between the layers.

[0041] The layer 20 is provided with components of a circuit that drives the pixel circuits PIX provided in the layer 30b. For example, the layer 20 may be provided with a gate driver 22, a circuit 21a that is a component of the source driver 21, a functional circuit 23, and the like. The gate driver 22 has a function of selecting the pixel circuit PIX to which image data is to be supplied. The source driver 21 has a function of supplying image data to the pixel circuit PIX. The functional circuit 23 may be a memory circuit that temporarily stores image data or correction data, a timing generation circuit, a power supply circuit, an arithmetic circuit, or the like.

[0042] The pair of drive circuits (gate driver 22, source driver 21) can be arranged, for example, in a rectangular region 25 when viewed from above. A plurality of regions 25 are arranged in a matrix, and the drive circuits in the regions 25 drive the divided pixel arrays 31 (plurality of pixel circuits PIX) on the regions 25, so that the entire display region can be divided into a plurality of regions and driven.

[0043] When the drive circuit is provided in the frame, the degree of freedom in arranging the drive circuit is limited, which limits the number of divisions that can be driven. On the other hand, in this configuration, the drive circuit can be arranged overlapping the pixel circuits, which increases the number of divisions that can be driven.

[0044] For example, if the number of regions 25 each having a pair of drive circuits is 32 (4 x 8), the display region can be divided into 32 regions and driven in parallel, allowing for high-speed display operations. Furthermore, the aforementioned foveated rendering becomes possible. The number of regions to be driven is not limited to this number and can be determined appropriately depending on the size, resolution, display function, and other factors of the display region.

[0045] Because the driver circuit and the functional circuit 23 are required to operate at high speed, it is preferable that the transistors constituting them are capable of high-speed operation. For example, a transistor having high mobility and containing silicon in a channel formation region (hereinafter referred to as a Si transistor) can be used as the transistor. In this case, the layer 20 can have a single-crystal silicon substrate, an SOI (Silicon on Insulator) substrate, a glass substrate with polycrystalline silicon formed on its surface, or the like.

[0046] The layer 30a may be provided with a circuit 21b, which is a component of the source driver 21. The layer 30b may also be provided with a divided pixel array 31. The divided pixel array 31 has a configuration in which a plurality of pixel circuits PIX are arranged in a matrix. The display area has a configuration in which the divided pixel arrays 31 are arranged in a matrix. Note that some of the transistors that make up the pixel circuit PIX may be provided in the layer 30a.

[0047] The circuit of the layer 30 (layers 30a and 30b) is preferably formed by a transistor having a thin-film semiconductor layer in a channel formation region. The thin-film semiconductor layer can be formed using a film formation process, and therefore can be easily formed on a Si transistor via an insulating layer without using a bonding process or the like.

[0048] For the semiconductor layer that can be formed as a thin film, polycrystalline silicon, amorphous silicon, metal oxide, or the like can be used. In particular, it is preferable to use metal oxide, which does not require a crystallization step or the like and can form a transistor with relatively high mobility.

[0049] Here, the circuit 21b provided in the layer 30a is preferably formed using a transistor suitable for high-speed operation of the circuit because it is a component of the source driver 21. In one embodiment of the present invention, a vertical transistor using a metal oxide for a semiconductor layer (hereinafter referred to as a first OS transistor) is used as the transistor.

[0050] A vertical transistor is a transistor in which a channel formation region is provided in a semiconductor layer formed along the side surface of an insulating layer, and the channel length is determined depending on the thickness of the insulating layer. Vertical transistors have the advantage that the channel length can be formed short without relying heavily on lithography accuracy. By forming a transistor with a short channel length, the on-current can be increased. Therefore, vertical transistors can be said to be transistors suitable for high-speed circuit operation.

[0051] It is preferable to use a light-emitting element that does not require a light source as the display element of the pixel circuit PIX. As the light-emitting element, an organic EL element or a micro LED (Light Emitting Diode) can be used.

[0052] It is preferable that a pixel circuit PIX having a light-emitting element uses a plurality of transistors with different characteristics. Therefore, the pixel circuits PIX provided in the layer 30b use transistors whose channel lengths can be differentiated by a lithography process.

[0053] In one embodiment of the present invention, the transistor is a transistor (hereinafter referred to as a second OS transistor) that uses a metal oxide in a channel formation region and has a structure different from that of the first OS transistor. The second OS transistor may have a structure such as a planar transistor, a staggered transistor, an inverted staggered transistor, a trench transistor, or a fin transistor. The second OS transistor may have either a top-gate or bottom-gate transistor structure. Note that the first OS transistor provided in the layer 30 a can also be used as some of the transistors included in the pixel circuit PIX.

[0054] 2A to 2C are diagrams showing an example of the arrangement of a pair of drive circuits (a source driver 21 and a gate driver 22) and a functional circuit 23 provided in the region 25 shown in Fig. 1, and a divided pixel array 31 provided thereon. The pair of drive circuits can drive the divided pixel array 31 provided on the region 25.

[0055] 2A shows an example in which a circuit 21b and a divided pixel array 31 (pixel circuit PIX) are provided over a pair of driver circuit and functional circuit 23. The circuit 21b includes a first OS transistor provided in layer 30a, and the pixel circuit PIX includes a second OS transistor provided in layer 30b. The circuit 21b has an area overlapping with one or more of the circuit 21a, the gate driver 22, and the functional circuit 23. The circuit 21b also has an area overlapping with the pixel circuit PIX. This configuration is effective for narrowing the frame.

[0056] 2B is a modification of FIG. 2A. The circuit 21b includes a first OS transistor provided in the layer 30a, and the pixel circuit PIX includes the first OS transistor provided in the layer 30a and a second OS transistor provided in the layer 30b. The circuit 21b has an area overlapping with any one of the circuit 21a, the gate driver 22, and the functional circuit 23. The circuit 21b also has an area overlapping with the pixel circuit PIX.

[0057] This configuration not only narrows the frame but also facilitates high-performance pixels. Since the components of the pixel circuit PIX can be stacked, the number of transistors per unit area of ​​the pixel circuit PIX can be increased. This makes it easier to add a correction circuit or the like to the pixel circuit PIX.

[0058] 2C shows an example in which a circuit 21b and a divided pixel array 31 (pixel circuit PIX) are provided on a pair of drive circuits and functional circuits 23. Note that FIG. 2C is illustrated with a portion divided for clarity.

[0059] The circuit 21b and the pixel circuit PIX each include a first OS transistor provided in the layer 30a and a second OS transistor provided in the layer 30b. The circuit 21b overlaps with at least one of the circuit 21a, the gate driver 22, and the functional circuit 23, but does not overlap with the pixel circuit PIX. That is, the circuit 21b is formed in a region between pixels.

[0060] In this configuration, the circuit 21b also includes the first OS transistor and the second OS transistor, and thus the circuit 21b can have a higher degree of freedom in design in addition to the advantages of FIG. 2B.

[0061] 3 shows a block diagram of the display device 10. The display device 10 includes a source driver 21 (circuits 21a and 21b), a gate driver 22, a functional circuit 23, a divided pixel array 31, and the like.

[0062] The circuit 21a, which is a component of the source driver 21, may include a receiver circuit 51, a serial-parallel converter circuit 52, a shift register circuit 53, a latch circuit 54, a level shift circuit 55, a voltage generation circuit 56 (R-DAC), a bandgap reference circuit 57 (BGR), a bias generation circuit 58 (BIAS-GEN), and a buffer amplifier circuit 59.

[0063] The circuit 21b, which is a component of the source driver 21, can include a latch circuit 34, a pass transistor logic circuit 35, etc. The latch circuit 34 may be an element of the circuit 21a.

[0064] In the circuit 21a, serial video data (digital data) is first input to a receiver circuit 51 and converted into parallel video data by a serial-to-parallel converter circuit 52. The parallel video data is distributed and held by a plurality of latch circuits 54 by a shift register circuit 53. Each piece of video data held in the plurality of latch circuits is boosted by a level shift circuit 55 and output to the circuit 21b.

[0065] The boosted parallel video data is input to the pass transistor logic circuit 35 via the plurality of latch circuits 34 included in the circuit 21b. In the pass transistor logic circuit 35, the parallel video data (digital data) is converted into analog data and output to the buffer amplifier circuit 59. The analog data is amplified by the buffer amplifier circuit 59 and output as analog video data to the pixel circuits PIX included in the divided pixel array 31.

[0066] Here, the pass transistor logic circuit 35 is a circuit that has the function of converting input digital data into analog data. The pass transistor logic circuit 35 requires a large number of transistors depending on the number of gradations of the video data, and therefore occupies a relatively large area. Furthermore, to increase the output current of the pass transistor logic circuit 35, it is preferable that the transistors that make up the circuit have a high withstand voltage.

[0067] Therefore, it is not necessarily appropriate to form the pass transistor logic circuit 35 in the layer 20 using Si transistors, as with other circuits that handle digital data. The pass transistor logic circuit 35 can also be configured as a unipolar circuit, not a CMOS circuit. Therefore, in one embodiment of the present invention, the pass transistor logic circuit 35 is formed in the layer 30 using first OS transistors as an element of the circuit 21b.

[0068] Since a transistor using metal oxide has a lower off-state current than a transistor using silicon, there is almost no fluctuation in data value due to the influence of a leakage current of the transistor during transmission or temporary storage of analog data. Furthermore, a transistor using metal oxide can withstand higher voltage than a transistor using silicon. Furthermore, the first OS transistor has a short channel length and is easily increased in on-state current, making it suitable for high-speed circuit operation. Therefore, by using the first OS transistor in the pass-transistor logic circuit 35, processing and transmission of a relatively high-voltage analog signal can be performed quickly and reliably.

[0069] Furthermore, by providing the pass transistor logic circuit 35 in the layer 30, the area in the layer 20 for arranging the functional circuit 23 and the like can be increased, which contributes to the high performance of the display device.

[0070] The latch circuit 34 is also preferably formed in the layer 30 as a component of the circuit 21b using a first OS transistor. The first OS transistor has a structure in which a semiconductor layer, an insulating layer, and a conductive layer are formed along the bottom and side surfaces of a trench, overlapping each other. This structure can also be used as a trench-type MOS capacitor with a small occupancy area by changing the connection form of the conductive layers. Alternatively, a trench-type MIM capacitor with a small occupancy area can be formed by removing the semiconductor layer. Therefore, the area occupied by the latch circuit 34, which is configured with a transistor and a capacitor, can be reduced. Note that the latch circuit 34 may also be provided in the layer 20 as a component of the circuit 21a.

[0071] Fig. 4 shows a configuration example of the pass transistor logic circuit 35. Fig. 4 also shows a configuration example of a voltage generating circuit 56 (R-DAC) connected to the pass transistor logic circuit 35.

[0072] The pass transistor logic circuit 35 is a circuit that has the function of converting input digital data into analog data, and the voltage generation circuit 56 is a circuit that has the function of generating a voltage of the analog data that is output from the pass transistor logic circuit 35. It can be said that the pass transistor logic circuit 35 and the voltage generation circuit 56 constitute a D / A (digital-to-analog) conversion circuit.

[0073] 4 is a circuit that outputs analog data corresponding to 8-bit digital data to an output terminal (OUT). Note that the number of bits of the input digital data is not limited to this.

[0074] First, the voltage generation circuit 56 will be described. Fig. 4 shows an example of a circuit of a resistor voltage division type (resistor string type) voltage generation circuit 56. The voltage generation circuit 56 is a circuit for generating a plurality of voltages (256 voltages in this case), and has a configuration in which a plurality of resistance elements RES are connected in series.

[0075] In the voltage generating circuit 56 shown in FIG. 4, a potential V ２５５ is applied to the other end, and a potential V ０ A plurality of resistor elements RES are used to provide a voltage V ２５５ -V ０ is divided by 256 and output as an output voltage to the pass transistor logic circuit 35. ２５５ corresponds to the output potential corresponding to the gradation value 255, and the potential V ０ corresponds to the output potential corresponding to the gradation value 0.

[0076] Here, the reference potential is V ２５５ And, V ０ The configuration using the two potentials V ２５５ and potential V ０The greater the number of reference potentials, the more stable the output potential of the voltage generating circuit 56 can be.

[0077] The configuration of the voltage generating circuit 56 is not limited to this, and various configurations can be used as long as the circuit is capable of generating a plurality of potentials.

[0078] Furthermore, although FIG. 4 shows a configuration in which one voltage generation circuit 56 is connected to one pass transistor logic circuit 35, a configuration in which one voltage generation circuit 56 is connected to a plurality of pass transistor logic circuits 35 and supplies potential may also be used.

[0079] Next, the pass transistor logic circuit 35 will be described. The pass transistor logic circuit 35 has a plurality of switches SW whose conduction state is controlled by input data DATA(0) through DATA(7) and their inverted data DATA_B(0) through DATA_B(7). Here, for example, DATA(0) is the first bit of 8-bit data, and DATA_B(7) is the inverted eighth bit of data.

[0080] By controlling the conductive state of the switch SW of the pass transistor logic circuit 35, the data is converted from digital to analog, and the voltage of the data output from the output terminal (OUT) becomes a voltage equivalent to the gradation voltage supplied to the divided pixel array 31.

[0081] Here, first OS transistors are used as the multiple switches SW. The pass-transistor logic circuit 35 receives digital data amplified by the level shift circuit 55 to increase the output current. Therefore, it is preferable that the transistors used in the pass-transistor logic circuit 35 have high withstand voltage.

[0082] A transistor having a metal oxide in a channel formation region has a higher breakdown voltage characteristic than a transistor having silicon, and is therefore suitable for circuits with a high driving voltage. Furthermore, by using a transistor having a short channel length and a large on-state current, such as the first OS transistor, the operating frequency and output characteristics of the pass-transistor logic circuit 35 can be improved.

[0083] Fig. 5A shows a circuit diagram of a latch circuit 34 applicable to the latch circuit 34. The latch circuit 34 shown in Fig. 5A is a sample-and-hold circuit capable of holding 1-bit digital data.

[0084] The latch circuit 34 includes two transistors and two capacitance elements. ＳＡＭＰ and latch signal S ＬＡＴ The latch circuit 34 has a function of sampling data DATA(i) (i is a bit number) in response to a precharge signal S ＰＲＥ Depending on the ＰＲＥ It can be precharged to

[0085] 5B shows an example in which two capacitors are formed using transistors. Each capacitor has a structure in which the source and drain of the transistor are connected. This allows the two transistors and the two capacitors to be formed in the same process. Note that using the first OS transistor as a capacitor has the advantage of easily increasing capacitance.

[0086] 5C shows an example of the configuration of the latch circuit 34 having two holding nodes. With this configuration, the next frame of data can be written to the node closer to the input side while the output data is held in the node closer to the output side of the two holding nodes. Specifically, when the latch signal S ＬＡＴ２ and latch signal S ＬＡＴ２Ｂ The data held in the node close to the input side is sampled in response to the sampling signal SＳＡＭＰ and latch signal S ＬＡＴ１ In response to this, data DATA(i) of the next frame is sampled and held at a node close to the input side. Note that each capacitive element shown in FIG. 5C may be formed using a transistor, as in FIG. 5B.

[0087] 6A to 6C are diagrams illustrating examples of circuits that can be applied to the pixel circuits PIX of the divided pixel array 31. FIG.

[0088] 6A includes a light-emitting device EL1, transistors M1, M2, and M3, and a capacitance element C1. Here, a light-emitting diode is used as the light-emitting device EL1. It is preferable to use an organic EL element that emits visible light as the light-emitting device EL1.

[0089] The gate of the transistor M1 is electrically connected to the wiring G1, one of the source or the drain is electrically connected to the wiring S1, and the other of the source or the drain is electrically connected to one electrode of the capacitor C1 and the gate of the transistor M2. One of the source or the drain of the transistor M2 is electrically connected to the wiring V2, and the other is electrically connected to the anode of the light-emitting device EL1 and one of the source or the drain of the transistor M3. The gate of the transistor M3 is electrically connected to the wiring G2, and the other of the source or the drain is electrically connected to the wiring V0. The cathode of the light-emitting device EL1 is electrically connected to the wiring V1.

[0090] A constant potential is supplied to the wiring V1 and the wiring V2. Light can be emitted by setting the anode side of the light-emitting device EL1 at a high potential and the cathode side at a low potential. The transistor M1 is controlled by a signal supplied to the wiring G1 and functions as a selection transistor for controlling the selection state of the circuit PIX1. The transistor M2 also functions as a drive transistor for controlling the current flowing through the light-emitting device EL1 in accordance with the potential supplied to its gate.

[0091] When transistor M1 is in a conductive state, the potential supplied to wiring S1 is supplied to the gate of transistor M2, and the light emission brightness of light-emitting device EL1 can be controlled according to the potential. Transistor M3 is controlled by a signal supplied to wiring G2. This allows the potential between transistor M3 and light-emitting device EL1 to be reset to a constant potential supplied from wiring V0, and a potential can be written to the gate of transistor M2 while the source potential of transistor M2 is stabilized.

[0092] 6B, each transistor included in the circuit PIX1 can be provided with two gates. In this specification, one of the two gates is referred to as a first gate or a front gate, and the other of the two gates is referred to as a second gate or a back gate.

[0093] 6B shows a configuration in which the front gate and back gate are connected and the same signal is supplied to them. This configuration can increase the on-state current. Note that a configuration in which the two gates are not connected and a constant potential is applied to the back gate may also be used. This configuration can control the threshold voltage of the transistor.

[0094] The structure in which a transistor has a back gate can also be applied to a circuit PIX2 described below. In addition, the circuits PIX1 and PIX2 may include both transistors with and without a back gate.

[0095] 6C shows an example of a circuit PIX2 that is different from the circuit PIX1. The circuit PIX2 has a boost function and includes a light-emitting device EL2, a transistor M4, a transistor M5, a transistor M6, a transistor M7, a capacitor C2, and a capacitor C3.

[0096] The transistor M4 has a gate electrically connected to the wiring G1, one of its source and drain electrically connected to the wiring S4, and the other of its source and drain electrically connected to one electrode of the capacitor C2, one electrode of the capacitor C3, and the gate of the transistor M6. The transistor M5 has a gate electrically connected to the wiring G6, one of its source and drain electrically connected to the wiring S5, and the other of its source and drain electrically connected to the other electrode of the capacitor C3.

[0097] One of the source and drain of transistor M6 is electrically connected to wiring V2, and the other is electrically connected to the anode of light-emitting device EL2 and one of the source and drain of transistor M7. The gate of transistor M7 is electrically connected to wiring G2, and the other of the source and drain is electrically connected to wiring V0. The cathode of light-emitting device EL2 is electrically connected to wiring V1.

[0098] The transistor M4 is controlled by a signal supplied to the wiring G1, and the transistor M5 is controlled by a signal supplied to the wiring G6. The transistor M6 functions as a drive transistor that controls the current flowing through the light-emitting device EL2 in accordance with the potential supplied to its gate.

[0099] The light emission luminance of the light-emitting device EL2 can be controlled according to the potential supplied to the gate of the transistor M6. The transistor M7 is controlled by a signal supplied to the wiring G2. The potential between the transistor M6 and the light-emitting device EL2 can be reset to a constant potential supplied from the wiring V0, and a potential can be written to the gate of the transistor M6 while the source potential of the transistor M6 is stabilized. Furthermore, the light emission of the light-emitting device EL2 can be suppressed by setting the potential supplied from the wiring V0 to the same potential as or lower than the wiring V1.

[0100] The boosting function of the circuit PIX2 will be described below.

[0101] First, the potential "D1" of the wiring S4 is supplied to the gate of the transistor M6 via the transistor M4, and at the same timing, the reference potential "V ｒｅｆ At this time, the capacitance element C3 is supplied with "D1-V ｒｅｆ Next, the gate of the transistor M6 is set to a floating state, and the potential "D2" of the wiring S5 is supplied to the other electrode of the capacitor C3 via the transistor M5. Here, the potential "D2" is a potential for addition.

[0102] At this time, the capacitance value of the capacitive element C3 is C ３ , the capacitance value of the capacitive element C2 is C ２ , the capacitance value of the gate of the transistor M6 is C Ｍ６ Then, the potential of the gate of the transistor M6 is D1+(C ３ / (C ３ +C ２ +C Ｍ６ ) × (D2 − V ｒｅｆ )) where C ３ The value of C ２ +C Ｍ６ If we assume that the value is sufficiently larger than the value of C ３ / (C ３ +C ２ +C Ｍ６ ) is close to 1. Therefore, the potential of the gate of the transistor M6 is "D1 + (D2 - V ｒｅｆ )" and D1 = D2, and V ｒｅｆ = 0, then "D1 + (D2 - V ｒｅｆ ))" = "2D1".

[0103] In other words, if the circuit is designed appropriately, a potential that is approximately twice the potential that can be input from the wiring S4 or S5 can be supplied to the gate of the transistor M6.

[0104] This effect allows a high voltage to be generated within the pixel circuit, thereby lowering the voltage input to the pixel circuit and reducing the power consumption of the drive circuit.

[0105] The circuit PIX2 may have the configuration shown in Fig. 6D. The circuit PIX2 shown in Fig. 6D differs from the circuit PIX2 shown in Fig. 6C in that it includes a transistor M8. The gate of the transistor M8 is electrically connected to a wiring G1, and one of the source or the drain is electrically connected to the other of the source or the drain of the transistor M5 and the other electrode of the capacitor C3, and the other of the source or the drain is electrically connected to a wiring V0. The one of the source or the drain of the transistor M5 is connected to a wiring S4.

[0106] 6C, the circuit PIX2 supplies the reference potential and the potential for addition to the other electrode of the capacitor C3 via the transistor M5 as described above. In this case, two wirings S4 and S5 are required, and the reference potential and the potential for addition must be alternately rewritten in the wiring S5.

[0107] 6D, the number of transistors M8 is increased, but a dedicated path for supplying the reference potential is provided, thereby reducing the number of wirings S5. Furthermore, the gate of transistor M8 can be connected to wiring G1, and wiring V0 can be used as the wiring for supplying the reference potential, so the number of wirings connected to transistor M8 does not increase. Furthermore, since the reference potential and the potential for addition are not alternately rewritten on a single wiring, high-speed operation with low power consumption is possible.

[0108] 6C and 6D, the reference potential "V ｒｅｆ In this case, a potential about three times the potential that can be input from the wiring S4 or S5 can be supplied to the gate of the transistor M6. Note that the inverted potential means a potential whose absolute value of the difference from a certain reference potential is the same (or approximately the same) but which is different from the original potential. The original potential is "D1", the inverted potential is "D1B", and the reference potential is V ０ When V ０ = (D1+D1B) / 2.

[0109] In the display device of this embodiment, an image may be displayed by causing the light-emitting device to emit light in a pulsed manner. By shortening the driving time of the light-emitting device, it is possible to reduce the power consumption and heat generation of the display device.

[0110] Here, each of the transistors included in the circuits PIX1 and PIX2 is preferably a transistor using a metal oxide (oxide semiconductor) for a semiconductor layer in which a channel is formed.

[0111] A transistor using a metal oxide, which has a wider band gap and a lower carrier density than silicon, can achieve an extremely small off-state current, which enables charge stored in a capacitor connected in series with the transistor to be held for a long period of time.

[0112] In other words, because data can be retained for a long time, image display can be maintained even if the frame frequency is reduced to, for example, 1 Hz or less. By reducing the frame frequency, the power consumption required for rewriting data can be reduced, thereby enabling the display device to consume less power. In addition, the ability to reduce the frame frequency is also effective for foveated rendering.

[0113] Although an example using n-channel transistors is shown in FIGS. 6A to 6D, p-channel transistors can also be used.

[0114] By manufacturing a display device using the above-described embodiment of the present invention, the frame of the display device can be narrowed, the functionality of the display device can be improved, and the display device can operate at high speed.

[0115] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0116] Embodiment 2 In this embodiment, a vertical transistor corresponding to the first OS transistor described in Embodiment 1 will be described.

[0117] 7A and 7B are diagrams illustrating a vertical transistor. Fig. 7A is a top view. Fig. 7B is a cross-sectional perspective view illustrating the depth direction of region d shown in Fig. 7A. Note that for clarity, some elements are omitted in Fig. 7A. Also, in Fig. 7B, the conductive layer 104 is indicated by a dashed line.

[0118] The vertical transistor 100 can be provided over a substrate 102. Note that in the case where the transistor 100 is formed in the layer 30a described in Embodiment 1, the substrate 102 corresponds to the layer 20.

[0119] The transistor 100 includes a conductive layer 104, a conductive layer 104e, an insulating layer 106, a semiconductor layer 108, a conductive layer 112a, and a conductive layer 112b. The conductive layer 104 is a gate wiring and is electrically connected to the conductive layer 104e, which functions as a gate electrode. A part of the insulating layer 106 functions as a gate insulating layer. The conductive layer 112a functions as one of a source electrode and a drain electrode. The conductive layer 112b functions as the other of the source electrode and the drain electrode.

[0120] In the semiconductor layer 108, the entire region that overlaps with the gate electrode between the source electrode and the drain electrode via the gate insulating layer functions as a channel formation region. In addition, in the semiconductor layer 108, the region in contact with the source electrode functions as a source region, and the region in contact with the drain electrode functions as a drain region.

[0121] A conductive layer 112a is provided on the substrate 102, an insulating layer 110 is provided on the conductive layer 112a, and a conductive layer 112b is provided on the insulating layer 110. The insulating layer 110 has a region sandwiched between the conductive layer 112a and the conductive layer 112b. The conductive layer 112a has a region overlapping with the conductive layer 112b with the insulating layer 110 interposed therebetween. The insulating layer 110 and the conductive layer 112b have an opening 141 that reaches the conductive layer 112a.

[0122] The conductive layer 112a and the conductive layer 112b may each have a stacked-layer structure. Figure 7B and other figures show an example in which the conductive layer 112a has a stacked-layer structure of the conductive layer 112a_1 and the conductive layer 112a_2. Note that Figure 7B shows an example in which the conductive layer 112a_1 has a region where the conductive layer 112a_2 is not provided and is in contact with the semiconductor layer 108. However, the conductive layer 112a_2 and the semiconductor layer 108 may also be in contact with each other.

[0123] The top surface shape of the opening 141 can be, for example, circular or elliptical. By making the top surface shape of the opening 141 circular, the processing accuracy when forming the opening 141 can be improved, and the opening 141 can be formed in a fine size. The top surface shape of the opening 141 may be a polygon such as a triangle, a quadrangle (including a rectangle, a rhombus, and a square), or a pentagon, or a polygon with rounded corners. The opening 141 can be formed using, for example, a resist mask.

[0124] The semiconductor layer 108 is provided to cover the opening 141. The semiconductor layer 108 has regions in contact with the top surface and side surfaces of the conductive layer 112b, the side surfaces of the insulating layer 110, and the top surface of the conductive layer 112a. The semiconductor layer 108 is electrically connected to the conductive layer 112a through the opening 141. The semiconductor layer 108 has a shape that follows the shapes of the top surface and side surfaces of the conductive layer 112b, the side surfaces of the insulating layer 110, and the top surface of the conductive layer 112a.

[0125] 7B and the like, the semiconductor layer 108 has a single-layer structure; however, one embodiment of the present invention is not limited to this. The semiconductor layer 108 may have a stacked structure of two or more layers.

[0126] The insulating layer 106 functioning as a gate insulating layer of the transistor 100 is provided over the semiconductor layer 108 , the conductive layer 112 b , and the insulating layer 110 so as to cover the recessed portion resulting from the opening 141 .

[0127] The conductive layer 104e of the transistor 100 is provided on the insulating layer 106 so as to fill the recess resulting from the opening 141. Here, it is preferable that an insulating layer 150 having an opening 151 that reaches the opening 141 and the insulating layer 106 is provided on the insulating layer 106.

[0128] The insulating layer 150 can be used as an insulating layer for forming a buried electrode in a damascene process. That is, the conductive layer 104e is provided on the insulating layer 106 so as to fill the recess resulting from the opening 141 and the opening 151 of the insulating layer 150. The conductive layer 104 can be formed on the conductive layer 104e and the insulating layer 150 that have been planarized in the damascene process.

[0129] In the opening 141, the conductive layer 104e has a region overlapping with the semiconductor layer 108 with the insulating layer 106 interposed therebetween. The conductive layer 104e also has a region overlapping with the conductive layer 112a with the insulating layer 106 and the semiconductor layer 108 interposed therebetween and a region overlapping with the conductive layer 112b. The conductive layer 104e preferably covers an end of the conductive layer 112b on the opening 141 side. With this structure, the entire region of the semiconductor layer 108 that overlaps with the gate electrode with the gate insulating layer interposed therebetween can function as a channel formation region between the source electrode and the drain electrode.

[0130] The transistor 100 is a so-called top-gate transistor having a gate electrode above the semiconductor layer 108. Furthermore, since the bottom surface of the semiconductor layer 108 is in contact with a source electrode or a drain electrode, the transistor 100 can be called a TGBC (Top Gate Bottom Contact) transistor.

[0131] The conductive layers 112a, 112b, 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.

[0132] In the transistor of one embodiment of the present invention, the conductive layers 112a, 112b, 104, and 112b, which function as wirings, can be formed by processing different conductive films. Therefore, one or more other conductive layers can be overlapped with any one of the conductive layers, which increases the flexibility of the layout and reduces the area occupied by the circuit.

[0133] Next, a description will be given of the channel length and the channel width of the transistor 100. 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, a region in contact with the conductive layer 112b functions as the other of the source region and the drain region, and a region between the source region and the drain region functions as a channel formation region.

[0134] The channel length of the transistor 100 is the distance between the source region and the drain region. In Figure 7B, the channel length L100 of the transistor 100 is indicated by a dashed double-headed arrow. In a cross-sectional view, the channel length L100 is the distance between the edge of the region where the semiconductor layer 108 and the conductive layer 112a contact each other and the edge of the region where the semiconductor layer 108 and the conductive layer 112b contact each other.

[0135] In other words, the channel length L100 is determined by the film thickness of the insulating layer 110 and the angle between the side surface of the insulating layer 110 on the opening 141 side and the upper surface of the conductive layer 112a, and is not affected by the performance of the exposure equipment used to fabricate the transistor. Therefore, the channel length L100 can be set to a value smaller than the limit resolution of the exposure equipment, and a transistor with a fine size can be realized.

[0136] The on-state current of the transistor 100 can be increased by reducing the channel length L100. A circuit capable of high-speed operation can be manufactured by using the transistor 100. Furthermore, the transistor can be miniaturized, which enables the area occupied by the circuit to be reduced.

[0137] 7B and the like show a cross-sectional configuration in which the side surface of the insulating layer 110 on the opening 141 side has a straight line shape; however, one embodiment of the present invention is not limited to this. In a cross-sectional view, the side surface of the insulating layer 110 on the opening 141 side may have a curved line shape, or the side surface may have both a straight line region and a curved line region.

[0138] The channel width of the transistor 100 is the width of the source region or the width of the drain region in a direction perpendicular to the channel length direction. That is, the channel width is the width of the region where the semiconductor layer 108 and the conductive layer 112a contact or the width of the region where the semiconductor layer 108 and the conductive layer 112b contact in a direction perpendicular to the channel length direction. Here, the channel width of the transistor 100 is described as the width of the region where the semiconductor layer 108 and the conductive layer 112b contact in a direction perpendicular to the channel length direction. In Figures 7A and 7B, the channel width W100 of the transistor 100 is indicated by a solid double-headed arrow. The channel width W100 is the length of the bottom end of the conductive layer 112b on the opening 141 side in a top view.

[0139] The channel width W100 is determined by the top surface shape of the opening 141. When the top surface shape of the opening 141 is circular, the diameter of the opening 141 is set to D141, and the film thickness of the conductive layer 112b is assumed to be negligible, then the channel width W100 can be calculated as "D141 × π".

[0140] That is, the transistor 100 has a large channel width relative to the area it occupies. By increasing the channel width W100, the on-state current of the transistor 100 can be increased, and a circuit capable of high-speed operation can be manufactured.

[0141] Components included in the transistor 100 of this embodiment will be described below.

[0142] [Transistor Components] [Semiconductor Layer 108] The semiconductor material that can be used for the semiconductor layer 108 is not particularly limited. For example, an elemental semiconductor or a compound semiconductor can be used. As the elemental semiconductor, for example, silicon or germanium can be used. As the compound semiconductor, for example, gallium arsenide and silicon germanium can be used. As the compound semiconductor, an organic substance having semiconductor properties or a metal oxide (also called an oxide semiconductor) having semiconductor properties can be used. Note that these semiconductor materials may contain impurities as dopants.

[0143] The crystallinity of the semiconductor material used for the semiconductor layer 108 is not particularly limited, and any of an amorphous semiconductor and a crystalline semiconductor (a single-crystalline semiconductor, a polycrystalline semiconductor, a microcrystalline semiconductor, or a semiconductor having a crystalline region in part) may be used. Use of a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0144] The semiconductor layer 108 preferably includes a metal oxide (oxide semiconductor). 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 includes at least indium (In) or zinc (Zn). The metal oxide preferably includes two or three elements selected from indium, element M, and zinc. The element M is one or more elements selected from gallium, aluminum, silicon, boron, yttrium, tin, antimony, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, cobalt, and magnesium. In particular, the element M is preferably one or more elements selected from aluminum, gallium, yttrium, and tin. The element M is more preferably gallium.

[0145] The semiconductor layer 108 can be formed using, for example, indium oxide, indium gallium oxide (In—Ga oxide), indium zinc oxide (In—Zn oxide), indium tin oxide (In—Sn oxide), indium titanium oxide (In—Ti oxide), gallium zinc oxide (Ga—Zn oxide), indium aluminum zinc oxide (In—Al—Zn oxide, also referred to as IAZO), indium tin zinc oxide (In—Sn—Zn oxide), 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), indium gallium aluminum zinc oxide (In—Ga—Al—Zn oxide, also referred to as IGAZO or IAGZO), or indium tin oxide containing silicon.

[0146] Here, the composition of the metal oxide in the semiconductor layer 108 significantly affects the electrical characteristics and reliability of the transistor 100. For example, 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, a transistor with a large on-state current can be realized.

[0147] When an In—Zn oxide is used for the semiconductor layer 108, it is preferable to use a metal oxide in which the atomic ratio of indium is equal to or greater than the atomic ratio of zinc. For example, a metal oxide in which the atomic ratio of metal elements is In:Zn=1:1, In:Zn=2:1, In:Zn=3:1, In:Zn=4:1, In:Zn=5:1, In:Zn=7:1, or In:Zn=10:1, or a ratio close to these, can be used.

[0148] When an In—Sn oxide is used for the semiconductor layer 108, it is preferable to use a metal oxide in which the atomic ratio of indium is equal to or greater than the atomic ratio of tin. For example, a metal oxide in which the atomic ratio of metal elements is In:Sn=1:1, In:Sn=2:1, In:Sn=3:1, In:Sn=4:1, In:Sn=5:1, In:Sn=7:1, or In:Sn=10:1, or a ratio close to these values, can be used.

[0149] When an In-Sn-Zn oxide is used for the semiconductor layer 108, a metal oxide in which the atomic ratio of indium is higher than that of tin can be used. Furthermore, it is preferable to use a metal oxide in which the atomic ratio of zinc is higher than that of tin. For example, the atomic ratios of metal elements may be In:Sn:Zn=2:1:3, In:Sn:Zn=3:1:2, In:Sn:Zn=4:2:3, In:Sn:Zn=4:2:4.1, In:Sn:Zn=5:1:3, In:Sn:Zn=5:1:6, In:Sn:Zn=5:1:7, In:Sn:Zn=5:1:8, In:Sn:Zn=6:1:6, In :Sn:Zn=10:1:3, In:Sn:Zn=10:1:6, In:Sn:Zn=10:1:7, In:Sn:Zn=10:1:8, In:Sn:Zn=5:2:5, In:Sn:Zn=10:1:10, In:Sn:Zn=20:1:10, In:Sn:Zn=40:1:10, or metal oxides thereof having a ratio close to these can be used.

[0150] When an In-Al-Zn oxide is used for the semiconductor layer 108, a metal oxide in which the atomic ratio of indium is higher than that of aluminum can be used. Furthermore, it is preferable to use a metal oxide in which the atomic ratio of zinc is higher than that of aluminum. For example, the atomic ratios of metal elements may be In:Al:Zn=2:1:3, In:Al:Zn=3:1:2, In:Al:Zn=4:2:3, In:Al:Zn=4:2:4.1, In:Al:Zn=5:1:3, In:Al:Zn=5:1:6, In:Al:Zn=5:1:7, In:Al:Zn=5:1:8, In:Al:Zn=6:1:6, In In:Al:Zn=10:1:3, In:Al:Zn=10:1:6, In:Al:Zn=10:1:7, In:Al:Zn=10:1:8, In:Al:Zn=5:2:5, In:Al:Zn=10:1:10, In:Al:Zn=20:1:10, In:Al:Zn=40:1:10, or metal oxides thereof having a similar ratio can be used.

[0151] When an In—Ga—Zn oxide is used for the semiconductor layer 108, a metal oxide in which the atomic ratio of indium to the sum of the atomic numbers of all contained metal elements is higher than the atomic ratio of gallium can be used. Furthermore, it is more preferable to use a metal oxide in which the atomic ratio of zinc is higher than the atomic ratio of gallium. For example, the semiconductor layer 108 may have atomic ratios of metal elements of In:Ga:Zn=2:1:3, In:Ga:Zn=3:1:2, In:Ga:Zn=4:2:3, In:Ga:Zn=4:2:4.1, In:Ga:Zn=5:1:3, In:Ga:Zn=5:1:6, In:Ga:Zn=5:1:7, In:Ga:Zn=5:1:8, or In:Ga:Zn=6:1. :6, In:Ga:Zn=10:1:3, In:Ga:Zn=10:1:6, In:Ga:Zn=10:1:7, In:Ga:Zn=10:1:8, In:Ga:Zn=5:2:5, In:Ga:Zn=10:1:10, In:Ga:Zn=20:1:10, In:Ga:Zn=40:1:10, or metal oxides thereof can be used.

[0152] When an In-M-Zn oxide is used for the semiconductor layer 108, a metal oxide in which the atomic ratio of indium to the sum of the atomic numbers of all contained metal elements is higher than the atomic ratio of the element M can be used. Furthermore, it is more preferable to use a metal oxide in which the atomic ratio of zinc is higher than the atomic ratio of the element M. For example, the semiconductor layer 108 may have atomic ratios of metal elements of In:M:Zn=2:1:3, 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: In:M:Zn=10:1:6, In:M:Zn=10:1:3, In:M:Zn=10:1:6, In:M:Zn=10:1:7, In:M:Zn=10:1:8, In:M:Zn=5:2:5, In:M:Zn=10:1:10, In:M:Zn=20:1:10, In:M:Zn=40:1:10, or metal oxides thereof having a similar structure can be used.

[0153] By increasing the indium content of the metal oxide, a transistor with a large on-state current can be obtained. By applying the transistor to a transistor that requires a high on-state current, a circuit with excellent electrical characteristics can be formed.

[0154] The composition of the metal oxide can be analyzed by, for example, energy dispersive X-ray spectrometry (EDX), X-ray photoelectron spectrometry (XPS), inductively coupled plasma mass spectrometry (ICP-MS), or inductively coupled plasma atomic emission spectrometry (ICP-AES). Alternatively, a combination of these techniques may be used for the analysis. For elements with low content, the actual content may differ from the content obtained by analysis due to the influence of analytical accuracy. For example, when the content of element M is low, the content of element M obtained by analysis may be lower than the actual content.

[0155] In this specification, a "nearby composition" includes a range of ±30% of the desired atomic ratio. For example, when an atomic ratio is described as In:M:Zn = 4:2:3 or a composition thereabout, this includes a case where, when the atomic ratio of indium is 4, the atomic ratio of M is 1 or more and 3 or less, and the atomic ratio of zinc is 2 or more and 4 or less. Furthermore, when an atomic ratio is described as In:M:Zn = 5:1:6 or a composition thereabout, this includes a case where, when the atomic ratio of indium is 5, the atomic ratio of M is more than 0.1 and 2 or less, and the atomic ratio of zinc is 5 or more and 7 or less. Furthermore, when an atomic ratio is described as In:M:Zn = 1:1:1 or a composition thereabout, this includes a case where, when the atomic ratio of indium is 1, the atomic ratio of M is more than 0.1 and 2 or less, and the atomic ratio of zinc is more than 0.1 and 2 or less.

[0156] The metal oxide can be preferably formed by sputtering or atomic layer deposition (ALD). When forming a metal oxide by sputtering, the atomic ratio of the target may differ from the atomic ratio of the metal oxide. In particular, the atomic ratio of zinc in the metal oxide may be smaller than the atomic ratio of the target. Specifically, the atomic ratio of zinc in the metal oxide may be approximately 40% to 90% of the atomic ratio of zinc contained in the target.

[0157] 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.

[0158] The two or more metal oxide layers included in the semiconductor layer 108 may have different compositions. For example, a stacked structure of a first metal oxide layer having an atomic ratio of In:M:Zn=1:3:4 or a composition similar thereto and a second metal oxide layer having an atomic ratio of In:M:Zn=1:1:1 or a composition similar thereto, provided on the first metal oxide layer, can be preferably used. Furthermore, it is particularly preferable to use gallium or aluminum as the element M. 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) can be used.

[0159] It is preferable to use a crystalline metal oxide layer for the semiconductor layer 108. For example, a metal oxide layer having a c-axis aligned crystal (CAAC) structure, a polycrystalline structure, a nanocrystalline (nc) structure, or the like can be used. 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 transistor can be realized.

[0160] 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.

[0161] 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, where the second metal oxide layer has 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. 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 with the same composition, for example, the same sputtering target can be used to form the layers, thereby reducing manufacturing costs. For example, by using the same sputtering target and varying the oxygen flow rate, a stacked structure of two or more metal oxide layers with different crystallinity can be formed. Note that the two or more metal oxide layers included in the semiconductor layer 108 may have different compositions.

[0162] 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 −３ The 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:

[0163] A transistor using an oxide semiconductor (hereinafter referred to as an OS transistor) has significantly higher field-effect mobility than a transistor using amorphous silicon. Furthermore, an OS transistor has significantly lower source-drain leakage current in an off state (hereinafter also referred to as 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.

[0164] [Insulating Layer 110] When an oxide semiconductor is used for the semiconductor layer 108, an inorganic insulating material can be suitably used for the insulating layer 110 (the insulating layer 110a, the insulating layer 110b, and the insulating layer 110c). Note that the insulating layer 110 may have a stacked structure of an inorganic insulating material and an organic insulating material.

[0165] The inorganic insulating material can be one or more of oxide, oxynitride, nitride oxide, and nitride. For example, the insulating layer 110 can be one or more of silicon oxide, silicon oxynitride, aluminum oxide, hafnium oxide, yttrium oxide, zirconium oxide, gallium oxide, tantalum oxide, magnesium oxide, lanthanum oxide, cerium oxide, neodymium oxide, silicon nitride, silicon nitride oxide, and aluminum nitride.

[0166] In this specification and the like, an oxynitride refers to a material whose composition contains more oxygen than nitrogen. A nitride oxide refers to a material whose composition contains more nitrogen than oxygen. For example, silicon oxynitride refers to a material whose composition contains more oxygen than nitrogen, and silicon nitride oxide refers to a material whose composition contains more nitrogen than oxygen.

[0167] The insulating layer 110b is preferably formed using an oxide or an oxynitride. The insulating layer 110b is preferably formed using a film that releases oxygen when heated. For example, silicon oxide or silicon oxynitride can be suitably used for the insulating layer 110b.

[0168] When the insulating layer 110b releases oxygen, oxygen can be supplied from the insulating layer 110b to the semiconductor layer 108. When oxygen is supplied from the insulating layer 110b to the semiconductor layer 108, particularly to the channel formation region of the semiconductor layer 108, oxygen vacancies (V Ｏ ) and V Ｏ H (defects in which hydrogen enters oxygen vacancies) can be reduced, resulting in a transistor with good electrical characteristics and high reliability. The insulating layer 110b preferably has a high oxygen diffusion coefficient. By increasing the oxygen diffusion coefficient of the insulating layer 110b, oxygen can be easily diffused in the insulating layer 110b, and oxygen can be efficiently supplied from the insulating layer 110b to the semiconductor layer 108. Other treatments for supplying oxygen to the semiconductor layer 108 include heat treatment in an atmosphere containing oxygen and plasma treatment in an atmosphere containing oxygen.

[0169] Oxygen vacancies (V Ｏ ) and V Ｏ In particular, when the channel length L100 is short, oxygen vacancies (V Ｏ ) and V Ｏ For example, if VH is introduced from the source or drain region to the channel forming region, the influence of VH on the electrical characteristics and reliability will increase. Ｏ The diffusion of H increases the carrier concentration in the channel formation region, which may cause a change in the threshold voltage of the transistor 100 or a decrease in reliability. Ｏ The influence of the diffusion of H on the electrical characteristics and reliability becomes greater as the channel length L100 of the transistor 100 becomes shorter. 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 (V Ｏ ) and V Ｏ H can be reduced. Therefore, a transistor having a short channel length and having good electrical characteristics and high reliability can be realized.

[0170] The insulating layers 110a and 110c are preferably impermeable to oxygen. The insulating layers 110a and 110c function as blocking films that suppress oxygen from being released from the insulating layer 110b. Furthermore, the insulating layers 110a and 110c are preferably impermeable to hydrogen. The insulating layers 110a and 110c function as blocking films that suppress hydrogen from diffusing from outside the transistor to the semiconductor layer 108 through the insulating layer 110. The insulating layers 110a and 110c preferably have high film densities. Increasing the film densities of the insulating layers 110a and 110c can improve the blocking properties of oxygen and hydrogen. The film densities of the insulating layers 110a and 110c are preferably higher than that of the insulating layer 110b. When silicon oxide or silicon oxynitride is used for the insulating layer 110b, the insulating layers 110a and 110c can each preferably be made of, for example, silicon nitride, silicon nitride oxide, or aluminum oxide. The insulating layers 110a and 110c each preferably have a region with a higher nitrogen content than the insulating layer 110b. The insulating layers 110a and 110c can each be made of, for example, a material with a higher nitrogen content than the insulating layer 110b. The insulating layers 110a and 110c can each preferably be made of, for example, nitride or nitride oxide. The insulating layers 110a and 110c can each be made of, for example, silicon nitride or silicon nitride oxide.

[0171] When oxygen contained in the insulating layer 110b diffuses upward from a region of the insulating layer 110b that is not in contact with the semiconductor layer 108 (for example, the upper surface of the insulating layer 110b), the amount of oxygen supplied from the insulating layer 110b to the semiconductor layer 108 may decrease. By providing the insulating layer 110c on the insulating layer 110b, it is possible to prevent the oxygen contained in the insulating layer 110b from diffusing from a region of the insulating layer 110 that is not in contact with the semiconductor layer 108. Similarly, by providing the insulating layer 110a below the insulating layer 110b, it is possible to prevent the oxygen from diffusing downward from a region of the insulating layer 110 that is not in contact with the semiconductor layer 108. Therefore, the amount of oxygen supplied from the insulating layer 110b to the semiconductor layer 108 increases, and oxygen vacancies (V Ｏ ) and V Ｏ H can be reduced. Therefore, a highly reliable transistor can be obtained that exhibits favorable electrical characteristics.

[0172] The oxygen contained in the insulating layer 110b may oxidize the conductive layer 112a and the conductive layer 112b, resulting in an increase in resistance. Furthermore, the oxygen contained in the insulating layer 110b may oxidize the conductive layer 112a and the conductive layer 112b, resulting in a decrease in the amount of oxygen supplied from the insulating layer 110b to the semiconductor layer 108. 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, reducing oxygen vacancies (V Ｏ ) and V Ｏ H can be reduced, and a highly reliable transistor can be obtained that exhibits favorable electrical characteristics.

[0173] When hydrogen diffuses into the semiconductor layer 108, it reacts with oxygen atoms contained in the oxide semiconductor to form water, and oxygen vacancies (V Ｏ ) may be formed. ＯBy providing the insulating layer 110a and the insulating layer 110c, oxygen vacancies (V Ｏ ) and V Ｏ H can be reduced, and a highly reliable transistor can be obtained that exhibits favorable electrical characteristics.

[0174] The insulating layers 110a and 110c preferably have thicknesses that allow them to function as blocking films for oxygen and hydrogen. If the insulating layers 110a and 110c are too thin, their function as blocking films may be reduced. On the other hand, if the insulating layers 110a and 110c are too thick, the region of the semiconductor layer 108 in contact with the insulating layer 110b may be narrowed, and the amount of oxygen supplied from the insulating layer 110b to the semiconductor layer 108 may be reduced. The insulating layers 110a and 110c may each be thinner than the insulating layer 110b.

[0175] In the transistor 100, oxygen is supplied from the insulating layer 110 to the semiconductor layer 108, and oxygen vacancies (V Ｏ ) and V Ｏ Therefore, a transistor having good electrical characteristics and high reliability can be obtained.

[0176] Note that either the insulating layer 110a or the insulating layer 110c, or both of them, may not be provided.

[0177] [Conductive Layer 112a, Conductive Layer 112b, and Conductive Layer 104e] The conductive layers 112a, 112b, and 104e, which function as a source electrode, a drain electrode, or a gate electrode, can be formed using one or more of chromium, copper, aluminum, gold, silver, zinc, tantalum, titanium, tungsten, manganese, nickel, iron, cobalt, molybdenum, and niobium, or an alloy containing one or more of the above metals. The conductive layers 112a, 112b, and 104e can each be preferably formed using a low-resistance conductive material containing one or more of copper, silver, gold, and aluminum. Copper and aluminum are particularly preferred because of their excellent mass productivity.

[0178] The conductive layer 112a, the conductive layer 112b, and the conductive layer 104e can each be a metal oxide film (also referred to as an oxide conductor). Examples of oxide conductors (OC) include In—Sn oxide (ITO), In—W oxide, In—W—Zn oxide, In—Ti oxide, In—Ti—Sn oxide, In—Zn oxide, In—Sn—Si oxide (ITSO), and In—Ga—Zn oxide.

[0179] Here, oxide conductors (OC) will be explained. For example, 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 more conductive and becomes an electric conductor. A metal oxide that has become an electric conductor can be called an oxide conductor.

[0180] The conductive layers 112a, 112b, and 104e 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.

[0181] The conductive layer 112a, the conductive layer 112b, and the conductive layer 104e may each be a Cu-X alloy film (X is Mn, Ni, Cr, Fe, Co, Mo, Ta, or Ti). By using a Cu-X alloy film, they can be processed by a wet etching process, which makes it possible to reduce manufacturing costs.

[0182] Note that the conductive layer 112a, the conductive layer 112b, and the conductive layer 104e may be formed using the same material or different materials.

[0183] Here, the conductive layers 112a and 112b will be specifically described using an example in which the semiconductor layer 108 is formed using a metal oxide.

[0184] When an oxide semiconductor is used for the semiconductor layer 108, the conductive layers 112a and 112b may be oxidized by oxygen contained in the semiconductor layer 108, resulting in an increase in resistance. The conductive layers 112a and 112b may be oxidized by oxygen contained in the insulating layer 110b, resulting in an increase in resistance. Furthermore, the conductive layers 112a and 112b may be oxidized by oxygen contained in the semiconductor layer 108, resulting in an oxygen deficiency (V Ｏ The conductive layers 112a and 112b are oxidized by oxygen contained in the insulating layer 110b, which may decrease the amount of oxygen supplied from the insulating layer 110b to the semiconductor layer 108.

[0185] The conductive layers 112a and 112b are preferably made of a material that is resistant to oxidation. The conductive layers 112a and 112b are preferably made of an oxide conductor. For example, In—Sn oxide (ITO) or In—Sn—Si oxide (ITSO) can be suitably used. The conductive layer 112a may be made of a nitride conductor. Examples of nitride conductors include tantalum nitride and titanium nitride. The conductive layer 112a may have a stacked structure of the above-mentioned materials.

[0186] By using a material that is resistant to oxidation for the conductive layer 112a and the conductive layer 112b, it is possible to prevent oxidation by oxygen contained in the semiconductor layer 108 or oxygen contained in the insulating layer 110b, which would otherwise increase the resistance. Ｏ ) in the semiconductor layer 108 can be suppressed, and the amount of oxygen supplied from the insulating layer 110b to the semiconductor layer 108 can be increased. Ｏ ) and V Ｏ H can be reduced, and a highly reliable transistor can be obtained that exhibits favorable electrical characteristics.

[0187] Similarly, by using a material that is resistant to oxidation for the conductive layer 112b, an increase in resistance can be suppressed. Note that the conductive layers 112a and 112b may be formed using the same material or different materials.

[0188] The conductive layer 112b has a region in contact with the transistor 100. By using a material that is not easily oxidized for the conductive layer 112b, oxygen vacancies (V Ｏ ) and V Ｏ H can be reduced.

[0189] As described above, the conductive layer 112a and the conductive layer 112b in contact with the semiconductor layer 108 are preferably made of a material that is resistant to oxidation. However, when a material that is resistant to oxidation is used, the resistance may become high. Since the conductive layer 112a and the conductive layer 112b function as wirings, it is preferable that the resistance be low. Therefore, by using a material that is resistant to oxidation for the conductive layer 112a_1 having a region in contact with the semiconductor layer 108 and using a material with low resistance for the conductive layer 112a_2 not having a region in contact with the semiconductor layer 108, the resistance of the conductive layer 112a can be reduced. Furthermore, oxygen vacancies (V Ｏ ) and V Ｏ H can be reduced, and a highly reliable transistor can be obtained that exhibits favorable electrical characteristics.

[0190] As described above, when the channel length L100 is short, oxygen vacancies (V Ｏ ) and V Ｏ By using a material that is not easily oxidized for the conductive layer 112a_1, oxygen vacancies (V Ｏ ) and V Ｏ It is possible to suppress an increase in H. Therefore, a transistor having a short channel length, good electrical characteristics, and high reliability can be realized.

[0191] The conductive layer 112a_1 can preferably be made of one or more of an oxide conductor and a nitride conductor. The conductive layer 112a_2 can preferably be made of a material having lower resistance than the conductive layer 112a_1. The conductive layer 112a_2 can preferably 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 metals. Specifically, the conductive layer 112a_1 can preferably be made of In—Sn—Si oxide (ITSO), and the conductive layer 112a_2 can preferably be made of tungsten.

[0192] Note that the structure of the conductive layer 112a may be determined depending on the wiring resistance required for the conductive layer 112a. For example, when the length of the wiring (conductive layer 112a) is short and the required wiring resistance is relatively high, the conductive layer 112a may have a single-layer structure and may be made of a material that is not easily oxidized. On the other hand, when the length of the wiring (conductive layer 112a) is long and the required wiring resistance is relatively low, it is preferable that the conductive layer 112a have a stacked structure of a material that is not easily oxidized and a material that has low resistance.

[0193] The structure of the conductive layer 112a can be applied to other conductive layers.

[0194] [Insulating Layer 106] The insulating layer 106, which functions as a gate insulating layer, preferably has a low defect density. A low defect density in the insulating layer 106 enables a transistor to exhibit favorable electrical characteristics. Furthermore, the insulating layer 106 preferably has a high withstand voltage. A high withstand voltage of the insulating layer 106 enables a highly reliable transistor.

[0195] The insulating layer 106 can be formed using, for example, one or more of an oxide, an oxynitride, a nitride oxide, and a nitride having insulating properties. The insulating layer 106 can be formed using, for example, one or more of silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, aluminum nitride, hafnium oxide, hafnium oxynitride, gallium oxide, gallium oxynitride, yttrium oxide, yttrium oxynitride, and Ga—Zn oxide. The insulating layer 106 can be formed as a single layer or a stacked layer. The insulating layer 106 can be formed as, for example, a stacked layer structure of an oxide and a nitride.

[0196] In a miniaturized transistor, if the thickness of the gate insulating layer becomes thin, leakage current may increase. By using a material with a high relative dielectric constant (also called a high-k material) for the gate insulating layer, it is possible to reduce the voltage during transistor operation while maintaining the physical film thickness. Examples of high-k materials include gallium oxide, hafnium oxide, zirconium oxide, oxides containing aluminum and hafnium, oxynitrides containing aluminum and hafnium, oxides containing silicon and hafnium, oxynitrides containing silicon and hafnium, and nitrides containing silicon and hafnium.

[0197] The insulating layer 106 preferably releases little impurities (for example, water and hydrogen) from itself. When the insulating layer 106 releases little impurities, the impurities are prevented from diffusing into the semiconductor layer 108, and a highly reliable transistor can be obtained, which has good electrical characteristics.

[0198] Here, the insulating layer 106 will be specifically described using an example in which a metal oxide is used for the semiconductor layer 108 .

[0199] In order to improve the interface characteristics with the semiconductor layer 108, it is preferable to use an oxide for at least the side of the insulating layer 106 that is in contact with the semiconductor layer 108. For example, the insulating layer 106 can be preferably made of one or more of silicon oxide and silicon oxynitride. It is more preferable to use a film that releases oxygen by heating for the insulating layer 106.

[0200] The insulating layer 106 may have a stacked structure. The insulating layer 106 can have a stacked structure of an oxide film on the side in contact with the semiconductor layer 108 and a nitride film on the side in contact with the conductive layer 104e. For example, one or more of silicon oxide and silicon oxynitride can be preferably used as the oxide film. For example, silicon nitride can be preferably used as the nitride film.

[0201] [Insulating Layer 150] The insulating layer 150 can be made of the same material as the insulating layer 110. The insulating layer 150 is preferably formed of a material that has a high etching selectivity with respect to the insulating layer 106 and is more easily etched than the insulating layer 106. Note that although Fig. 7B shows an example in which the insulating layer 150 is a single layer, it may be a two-layer structure.

[0202] [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, 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 an organic resin substrate may be used as the substrate 102. Furthermore, any of these substrates on which semiconductor elements are provided may also be used as the substrate 102. The shape of the semiconductor substrate and the insulating substrate may be circular or rectangular.

[0203] 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.

[0204] The above is a description of the components of the transistor 100.

[0205] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0206] In this embodiment, a structure example of a display panel that can be applied to an electronic device of one embodiment of the present invention will be described. The display panel exemplified below can be applied to the display device 10 in Embodiment 1.

[0207] One embodiment of the present invention is a display panel having light-emitting elements (also referred to as light-emitting devices). The display panel has two or more pixels that emit light of different colors. Each pixel has a light-emitting element. Each light-emitting element has a pair of electrodes and an EL layer therebetween. The light-emitting element is preferably an organic EL element (organic electroluminescent element). Two or more light-emitting elements that emit light of different colors each have an EL layer containing a different light-emitting material. For example, a full-color display panel can be realized by having three types of light-emitting elements that emit red (R), green (G), or blue (B) light, respectively.

[0208] When fabricating a display panel with multiple light-emitting elements that emit different colors of light, it is necessary to form at least one layer containing a light-emitting material (light-emitting layer) in an island shape. To fabricate part or all of the EL layer separately, a method for forming island-shaped organic films by vapor deposition using a shadow mask such as a metal mask is known. However, this method can result in deviations from the design in the shape and position of the island-shaped organic film due to various factors, such as the accuracy of the metal mask, misalignment between the metal mask and the substrate, metal mask deflection, and spreading of the contours of the deposited film due to vapor scattering, making it difficult to achieve high-resolution and high-aperture display panels. Furthermore, during vapor deposition, the contours of the layer can become blurred, resulting in thinning of the edges. In other words, the thickness of the island-shaped light-emitting layer can vary depending on the location. Furthermore, when fabricating large, high-resolution, or high-definition display panels, there is a concern that low dimensional accuracy of the metal mask and deformation due to heat can reduce manufacturing yield. Therefore, measures have been taken to artificially increase the resolution (also known as pixel density) by adopting special pixel arrangements such as a pentile array.

[0209] In this specification, the term "island-like" refers to a state in which two or more layers formed of the same material in the same process are physically separated. For example, an island-like light-emitting layer refers to a state in which the light-emitting layer is physically separated from an adjacent light-emitting layer.

[0210] In one embodiment of the present invention, an EL layer is processed into a fine pattern by photolithography without using a shadow mask such as a fine metal mask (FMM). This makes it possible to realize a display panel with high definition and a large aperture ratio, which have been difficult to achieve until now. Furthermore, because the EL layer can be individually fabricated, a display panel with extremely vivid images, high contrast, and high display quality can be realized. For example, the EL layer may be processed into a fine pattern by using both a metal mask and photolithography.

[0211] Furthermore, the EL layer can be partially or entirely separated physically. This can suppress leakage current between adjacent light-emitting elements through a layer shared between the light-emitting elements (also referred to as a common layer). This can prevent crosstalk caused by unintended light emission, thereby realizing a display panel with extremely high contrast. In particular, a display panel with high current efficiency at low luminance can be realized.

[0212] One embodiment of the present invention can also be a display panel that combines a white-emitting light-emitting element and a color filter. In this case, light-emitting elements provided in pixels (subpixels) that emit light of different colors can have the same structure, and all layers can be common layers. Furthermore, part or all of each EL layer can be separated by a process using photolithography. This suppresses leakage current through the common layer, thereby achieving a display panel with high contrast. In particular, in an element having a tandem structure in which multiple light-emitting layers are stacked via a highly conductive intermediate layer, leakage current through the intermediate layer can be effectively prevented, thereby achieving a display panel that combines high brightness, high definition, and high contrast.

[0213] When the EL layer is processed using lithography, a portion of the light-emitting layer may be exposed, which may cause deterioration. Therefore, it is preferable to provide an insulating layer that covers at least the side surfaces of the island-shaped light-emitting layer. The insulating layer may also be configured to cover a portion of the top surface of the island-shaped EL layer. The insulating layer is preferably made of a material that has barrier properties against water and oxygen. For example, an inorganic insulating film that is less likely to diffuse water or oxygen can be used. This suppresses deterioration of the EL layer and realizes a highly reliable display panel.

[0214] Furthermore, there is a region (recess) between two adjacent light-emitting elements where the EL layer of either light-emitting element is not provided. When a common electrode, or a common electrode and a common layer, is formed to cover the recess, a phenomenon in which the common electrode is separated by a step at the edge of the EL layer (also called a step discontinuity) may occur, resulting in insulation of the common electrode on the EL layer. Therefore, it is preferable to use a configuration in which the local step located between two adjacent light-emitting elements is filled with a resin layer functioning as a planarizing film (also called LFP: Local Filling Planarization). The resin layer functions as a planarizing film. This suppresses step discontinuity in the common layer or common electrode, thereby achieving a highly reliable display panel.

[0215] A more specific example of the structure of a display panel according to one embodiment of the present invention will be described below with reference to the drawings.

[0216] 8A is a schematic top view of a display panel 200 according to one embodiment of the present invention. The display panel 200 includes a plurality of light-emitting elements 210R that exhibit red light, a plurality of light-emitting elements 210G that exhibit green light, and a plurality of light-emitting elements 210B that exhibit blue light over a layer 201. In FIG. 8A, the light-emitting regions of the light-emitting elements are labeled with R, G, and B to easily distinguish the light-emitting elements from one another. Note that the layer 201 can be an element included in the layer 30b described in Embodiment 1, for example.

[0217] The light-emitting elements 210R, 210G, and 210B are arranged in a matrix. Fig. 8A shows a so-called stripe arrangement, in which light-emitting elements of the same color are arranged in one direction. The arrangement of the light-emitting elements is not limited to this, and other arrangements such as an S-stripe arrangement, a delta arrangement, a Bayer arrangement, or a zigzag arrangement may also be used. Alternatively, a pentile arrangement or a diamond arrangement may also be used.

[0218] As the light-emitting element 210R, the light-emitting element 210G, and the light-emitting element 210B, for example, an OLED (organic light-emitting diode) or a QLED (quantum-dot light-emitting diode) is preferably used. Examples of the light-emitting material contained in the EL element include a material that emits fluorescence (fluorescent material), a material that emits phosphorescence (phosphorescent material), and a material that exhibits thermally activated delayed fluorescence (thermally activated delayed fluorescence: TADF material). As the light-emitting material contained in the EL element, not only organic compounds but also inorganic compounds (such as quantum dot materials) can be used.

[0219] 8A also shows a connection electrode 211C that is electrically connected to the common electrode 213. The connection electrode 211C is given a potential (e.g., an anode potential or a cathode potential) to be supplied to the common electrode 213. The connection electrode 211C is provided outside the display area where the light-emitting elements 210R and the like are arranged.

[0220] The connection electrode 211C can be provided along the periphery of the display area. For example, it may be provided along one side of the periphery of the display area, or it may be provided over two or more sides of the periphery of the display area. That is, when the top surface shape of the display area is rectangular, the top surface shape of the connection electrode 211C can be a strip shape (rectangle), an L-shape, a U-shape (square bracket shape), a square shape, or the like.

[0221] 8B and 8C are schematic cross-sectional views corresponding to dashed dotted lines A1-A2 and A3-A4 in Fig. 8A, respectively. Fig. 8B shows a schematic cross-sectional view of light-emitting element 210R, light-emitting element 210G, and light-emitting element 210B, and Fig. 8C shows a schematic cross-sectional view of connection portion 230 where connection electrode 211C and common electrode 213 are connected.

[0222] The light-emitting element 210R has a pixel electrode 211R, an organic layer 212R, a common layer 214, and a common electrode 213. The light-emitting element 210G has a pixel electrode 211G, an organic layer 212G, a common layer 214, and a common electrode 213. The light-emitting element 210B has a pixel electrode 211B, an organic layer 212B, a common layer 214, and a common electrode 213. The common layer 214 and the common electrode 213 are provided in common to the light-emitting element 210R, the light-emitting element 210G, and the light-emitting element 210B.

[0223] The organic layer 212R of the light-emitting element 210R contains a light-emitting organic compound that emits at least red light. The organic layer 212G of the light-emitting element 210G contains a light-emitting organic compound that emits at least green light. The organic layer 212B of the light-emitting element 210B contains a light-emitting organic compound that emits at least blue light. The organic layer 212R, the organic layer 212G, and the organic layer 212B can also be called EL layers, and each contains at least a layer containing a light-emitting substance (light-emitting layer).

[0224] Hereinafter, when describing matters common to light-emitting element 210R, light-emitting element 210G, and light-emitting element 210B, they may be referred to as light-emitting element 210. Similarly, when describing matters common to components distinguished by alphabets, such as organic layer 212R, organic layer 212G, and organic layer 212B, they may be described using reference numerals without the alphabets.

[0225] The organic layer 212 and the common layer 214 can each independently have one or more of an electron injection layer, an electron transport layer, a hole injection layer, and a hole transport layer. For example, the organic layer 212 can have a stacked structure of a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer from the pixel electrode 211 side, and the common layer 214 can have an electron injection layer.

[0226] The pixel electrode 211R, pixel electrode 211G, and pixel electrode 211B are provided for each light-emitting element. The common electrode 213 and common layer 214 are provided as a continuous layer common to each light-emitting element. A conductive film transmissive to visible light is used for either the pixel electrode or the common electrode 213, and a conductive film reflective to visible light is used for the other. By making each pixel electrode transmissive and the common electrode 213 reflective, a bottom-emission display panel can be achieved. Conversely, by making each pixel electrode reflective and the common electrode 213 transmissive, a top-emission display panel can be achieved. Note that by making both the pixel electrodes and the common electrode 213 transmissive, a dual-emission display panel can be achieved.

[0227] A protective layer 221 is provided on the common electrode 213 to cover the light emitting elements 210R, 210G, and 210B. The protective layer 221 has a function of preventing impurities such as water from diffusing from above into each light emitting element.

[0228] The edge of the pixel electrode 211 preferably has a tapered shape. When the edge of the pixel electrode 211 has a tapered shape, the organic layer 212 provided along the edge of the pixel electrode 211 can also have a tapered shape. By tapering the edge of the pixel electrode 211, the coverage of the organic layer 212 provided over the edge of the pixel electrode 211 can be improved. Furthermore, by tapering the side surface of the pixel electrode 211, foreign matter (for example, also referred to as dust or particles) during the manufacturing process can be easily removed by a process such as cleaning, which is preferable.

[0229] In this specification and the like, the term "tapered shape" refers to a shape in which at least a part of a side surface of a structure is inclined with respect to a substrate surface. For example, it is preferable that the structure has a region in which the angle between the inclined side surface and the substrate surface (also referred to as the taper angle) is less than 90°.

[0230] The organic layer 212 is processed into an island shape using photolithography. As a result, the angle between the top surface and the side surface of the organic layer 212 at its edge is close to 90 degrees. On the other hand, an organic film formed using FMM (Fine Metal Mask) or the like tends to become gradually thinner closer to the edge. For example, the top surface is formed in a sloped shape over a range of 1 μm to 10 μm, making it difficult to distinguish between the top surface and the side surface.

[0231] Between two adjacent light emitting elements, there are an insulating layer 225, a resin layer 226 and a layer 228.

[0232] Between two adjacent light-emitting elements, the side surfaces of the organic layers 212 face each other with the resin layer 226 interposed therebetween. The resin layer 226 is located between the two adjacent light-emitting elements and is provided so as to fill the ends of each organic layer 212 and the region between the two organic layers 212. The resin layer 226 has a smooth, convex upper surface, and a common layer 214 and a common electrode 213 are provided to cover the upper surface of the resin layer 226.

[0233] The resin layer 226 functions as a planarization film that fills in a step between two adjacent light-emitting elements. By providing the resin layer 226, it is possible to prevent a phenomenon (also called step disconnection) in which the common electrode 213 is divided by a step at the end of the organic layer 212, and the common electrode on the organic layer 212 is isolated. The resin layer 226 can also be called LFP (Local Filling Planarization).

[0234] An insulating layer containing an organic material can be suitably used as the resin layer 226. For example, acrylic resin, polyimide resin, epoxy resin, imide resin, polyamide resin, polyimideamide resin, silicone resin, siloxane resin, benzocyclobutene resin, phenol resin, precursors of these resins, etc. can be used as the resin layer 226. Alternatively, organic materials such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or alcohol-soluble polyamide resin can be used as the resin layer 226.

[0235] Furthermore, a photosensitive resin can be used as the resin layer 226. A photoresist can be used as the photosensitive resin. The photosensitive resin can be a positive-type material or a negative-type material.

[0236] The resin layer 226 may contain a material that absorbs visible light. For example, the resin layer 226 itself may be made of a material that absorbs visible light, or the resin layer 226 may contain a pigment that absorbs visible light. For example, the resin layer 226 may be a resin that can be used as a color filter that transmits red, blue, or green light and absorbs other light, or a resin that contains carbon black as a pigment and functions as a black matrix.

[0237] The insulating layer 225 is provided in contact with the side surface of the organic layer 212. The insulating layer 225 is also provided to cover the upper end portion of the organic layer 212. A portion of the insulating layer 225 is provided in contact with the upper surface of the layer 201.

[0238] The insulating layer 225 is located between the resin layer 226 and the organic layer 212, and functions as a protective film for preventing the resin layer 226 from contacting the organic layer 212. If the organic layer 212 and the resin layer 226 come into contact with each other, the organic layer 212 may be dissolved by an organic solvent or the like used when forming the resin layer 226. Therefore, by providing the insulating layer 225 between the organic layer 212 and the resin layer 226, it is possible to protect the side surfaces of the organic layer 212.

[0239] The insulating layer 225 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 225. The insulating layer 225 may have a single-layer structure or a stacked-layer structure. Examples of oxide insulating films include a silicon oxide film, an aluminum oxide film, a magnesium oxide film, an indium gallium zinc oxide film, a gallium oxide film, a germanium oxide film, an yttrium oxide film, a zirconium oxide film, a lanthanum oxide film, a neodymium oxide film, a hafnium oxide film, and a tantalum oxide 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 and an aluminum oxynitride film. Examples of nitride oxide insulating films include a silicon nitride oxide film and an aluminum nitride oxide film. In particular, by using an inorganic insulating film such as a metal oxide film, an aluminum oxide film, or a silicon oxide film formed by an ALD method as the insulating layer 225, an insulating layer 225 with few pinholes and excellent protection of the EL layer can be formed.

[0240] In this specification and elsewhere, an oxynitride refers to a material whose composition contains more oxygen than nitrogen, and a nitride oxide refers to a material whose composition contains more nitrogen than oxygen. For example, silicon oxynitride refers to a material whose composition contains more oxygen than nitrogen, and silicon nitride oxide refers to a material whose composition contains more nitrogen than oxygen.

[0241] The insulating layer 225 can be formed by a sputtering method, a CVD method, a PLD method, an ALD method, or the like. The insulating layer 225 is preferably formed by an ALD method because it has good coverage.

[0242] Furthermore, a reflective film (e.g., a metal film containing one or more selected from silver, palladium, copper, titanium, aluminum, etc.) may be provided between the insulating layer 225 and the resin layer 226, so that the light emitted from the light-emitting layer is reflected by the reflective film, thereby improving the light extraction efficiency.

[0243] The layer 228 is a remaining portion of a protective layer (also referred to as a mask layer or a sacrificial layer) for protecting the organic layer 212 during etching of the organic layer 212. The layer 228 can be made of a material that can be used for the insulating layer 225. In particular, it is preferable to use the same material for the layer 228 and the insulating layer 225 because a common processing device or the like can be used for both.

[0244] In particular, inorganic insulating films such as metal oxide films such as aluminum oxide films and hafnium oxide films, or silicon oxide films formed by the ALD method have few pinholes and therefore have an excellent function of protecting the EL layer, and can be suitably used for the insulating layer 225 and the layer 228.

[0245] The protective layer 221 may have, for example, a single-layer structure or a multilayer structure including at least an inorganic insulating film. Examples of the inorganic insulating film include oxide films or nitride films such as a silicon oxide film, a silicon oxynitride film, a silicon nitride oxide film, a silicon nitride film, an aluminum oxide film, an aluminum oxynitride film, and a hafnium oxide film. Alternatively, the protective layer 221 may be made of a semiconductor material or a conductive material such as indium gallium oxide, indium zinc oxide, indium tin oxide, or indium gallium zinc oxide.

[0246] The protective layer 221 may also be a laminated film of an inorganic insulating film and an organic insulating film. For example, a configuration in which an organic insulating film is sandwiched between a pair of inorganic insulating films is preferable. Furthermore, it is preferable that the organic insulating film functions as a planarizing film. This allows the upper surface of the organic insulating film to be flat, improving the coverage of the inorganic insulating film thereon and enhancing the barrier properties. Furthermore, since the upper surface of the protective layer 221 is flat, when a structure (e.g., a color filter, a touch sensor electrode, a lens array, etc.) is provided above the protective layer 221, the influence of uneven shapes caused by the structure below can be reduced, which is preferable.

[0247] 8C shows a connection portion 230 where the connection electrode 211C and the common electrode 213 are electrically connected. In the connection portion 230, an opening is provided in the insulating layer 225 and the resin layer 226 above the connection electrode 211C. The connection electrode 211C and the common electrode 213 are electrically connected through the opening.

[0248] 8C shows the connection portion 230 where the connection electrode 211C and the common electrode 213 are electrically connected, but the common electrode 213 may be provided on the connection electrode 211C via the common layer 214. In particular, when a carrier injection layer is used for the common layer 214, the electrical resistivity of the material used for the common layer 214 is sufficiently low and the common layer 214 can be formed thin, so that there is often no problem even if the common layer 214 is located at the connection portion 230. This allows the common electrode 213 and the common layer 214 to be formed using the same masking mask, thereby reducing manufacturing costs.

[0249] [Configuration Example 2] The following describes a display panel having a configuration that is partially different from that of the above-described configuration example 1. Note that parts common to the above-described configuration example 1 will be referred to, and descriptions thereof may be omitted.

[0250] 9A shows a schematic cross-sectional view of the display panel 200a. The display panel 200a differs from the display panel 200 mainly in that the light-emitting elements have a different configuration and that a colored layer is provided.

[0251] The display panel 200a includes a light-emitting element 210W that emits white light. The light-emitting element 210W includes a pixel electrode 211, an organic layer 212W, a common layer 214, and a common electrode 213. The organic layer 212W emits white light. For example, the organic layer 212W may be configured to include two or more light-emitting materials whose emitted light colors are complementary to each other. For example, the organic layer 212W may be configured to include a light-emitting organic compound that emits red light, a light-emitting organic compound that emits green light, and a light-emitting organic compound that emits blue light. Alternatively, the organic layer 212W may be configured to include a light-emitting organic compound that emits blue light and a light-emitting organic compound that emits yellow light.

[0252] The organic layers 212W are separated between two adjacent light-emitting elements 210W. This makes it possible to suppress leakage current flowing between adjacent light-emitting elements 210W via the organic layers 212W, thereby suppressing crosstalk caused by the leakage current. This makes it possible to realize a display panel with high contrast and color reproducibility.

[0253] An insulating layer 222 that functions as a planarizing film is provided on the protective layer 221, and a coloring layer 216R, a coloring layer 216G, and a coloring layer 216B are provided on the insulating layer 222.

[0254] The insulating layer 222 can be an organic resin film or an inorganic insulating film with a flattened upper surface. The insulating layer 222 forms the surface on which the colored layers 216R, 216G, and 216B are formed. Therefore, the flat upper surface of the insulating layer 222 allows the thickness of the colored layers 216R and the like to be uniform, thereby improving the color purity of the light extracted from each light-emitting element. Note that if the thickness of the colored layers 216R and the like is uneven, the amount of light absorption varies depending on the location of the colored layer 216R, which may result in a decrease in color purity.

[0255] Configuration Example 3 FIG. 9B shows a schematic cross-sectional view of a display panel 200b.

[0256] The light-emitting element 210R has a pixel electrode 211, a conductive layer 215R, an organic layer 212W, and a common electrode 213. The light-emitting element 210G has a pixel electrode 211, a conductive layer 215G, an organic layer 212W, and a common electrode 213. The light-emitting element 210B has a pixel electrode 211, a conductive layer 215B, an organic layer 212W, and a common electrode 213. The conductive layer 215R, the conductive layer 215G, and the conductive layer 215B each have light-transmitting properties and function as an optical adjustment layer.

[0257] A microresonator (microcavity) structure can be realized by using a film that reflects visible light for pixel electrode 211 and a film that is both reflective and transparent to visible light for common electrode 213. In this case, by adjusting the thicknesses of conductive layer 215R, conductive layer 215G, and conductive layer 215B so as to provide optimal optical path lengths, even when organic layer 212 that emits white light is used, light of different wavelengths that are intensified can be obtained from light-emitting element 210R, light-emitting element 210G, and light-emitting element 210B.

[0258] Furthermore, colored layers 216R, 216G, and 216B are provided on the optical paths of the light emitting elements 210R, 210G, and 210B, respectively, so that light with high color purity can be obtained.

[0259] An insulating layer 223 is also provided to cover the edges of the pixel electrode 211 and the optical adjustment layer. The insulating layer 223 preferably has tapered edges. Providing the insulating layer 223 can improve coverage by the organic layer 212W, the common electrode 213, the protective layer 221, and the like that are formed thereon.

[0260] The organic layer 212W and the common electrode 213 are each provided as a continuous film in common to each light-emitting element, which is preferable because it can greatly simplify the manufacturing process of the display panel.

[0261] Here, it is preferable that the edge of pixel electrode 211 has a shape that is nearly perpendicular to the upper surface of layer 201. This makes it possible to form a steeply inclined portion on the surface of insulating layer 223, and to form a thin portion in part of organic layer 212W that covers this portion, or to divide part of organic layer 212W. Therefore, it is possible to suppress leakage current that occurs through organic layer 212W between adjacent light-emitting elements without processing organic layer 212W using a photolithography method or the like.

[0262] The above is a description of an example of the configuration of the display panel.

[0263] [Pixel Layout] The following mainly describes pixel layouts that are different from that shown in Fig. 8A. There are no particular limitations on the arrangement of light-emitting elements (sub-pixels), and various methods can be applied.

[0264] Examples of the top surface shape of the sub-pixel include a triangle, a quadrangle (including a rectangle and a square), a polygon such as a pentagon, a polygon with rounded corners, an ellipse, a circle, etc. Here, the top surface shape of the sub-pixel corresponds to the top surface shape of the light-emitting region of the light-emitting element.

[0265] An S-stripe arrangement is applied to pixel 250 shown in Fig. 10A. Pixel 250 shown in Fig. 10A is composed of three sub-pixels: light-emitting elements 210a, 210b, and 210c. For example, light-emitting element 210a may be a blue light-emitting element, light-emitting element 210b may be a red light-emitting element, and light-emitting element 210c may be a green light-emitting element.

[0266] The pixel 250 shown in FIG. 10B includes a light-emitting element 210a having a generally trapezoidal or triangular top surface shape with rounded corners, a light-emitting element 210b having a generally trapezoidal or triangular top surface shape with rounded corners, and a light-emitting element 210c having a generally rectangular or hexagonal top surface shape with rounded corners. Furthermore, the light-emitting element 210a has a larger light-emitting area than the light-emitting element 210b. In this manner, the shape and size of each light-emitting element can be determined independently. For example, the more reliable the light-emitting element, the smaller the size can be. For example, the light-emitting element 210a may be a green light-emitting element, the light-emitting element 210b may be a red light-emitting element, and the light-emitting element 210c may be a blue light-emitting element.

[0267] The pixels 224a and 224b shown in Fig. 10C are arranged in a Pentile arrangement. Fig. 10C shows an example in which a pixel 224a having a light-emitting element 210a and a light-emitting element 210b and a pixel 224b having a light-emitting element 210b and a light-emitting element 210c are alternately arranged. For example, the light-emitting element 210a may be a red light-emitting element, the light-emitting element 210b may be a green light-emitting element, and the light-emitting element 210c may be a blue light-emitting element.

[0268] 10D and 10E are arranged in a delta configuration. Pixel 224a has two light-emitting elements (light-emitting elements 210a and 210B) in the top row (first row) and one light-emitting element (light-emitting element 210c) in the bottom row (second row). Pixel 224b has one light-emitting element (light-emitting element 210c) in the top row (first row) and two light-emitting elements (light-emitting elements 210a and 210b) in the bottom row (second row). For example, light-emitting element 210a may be a red light-emitting element, light-emitting element 210b may be a green light-emitting element, and light-emitting element 210c may be a blue light-emitting element.

[0269] FIG. 10D shows an example in which each light-emitting element has a substantially rectangular top surface shape with rounded corners, and FIG. 10E shows an example in which each light-emitting element has a circular top surface shape.

[0270] 10F shows an example in which light-emitting elements of each color are arranged in a zigzag pattern. Specifically, when viewed from above, the positions of the upper edges of two light-emitting elements arranged in a column (e.g., light-emitting element 210a and light-emitting element 210B, or light-emitting element 210b and light-emitting element 210c) are offset. For example, light-emitting element 210a may be a red light-emitting element, light-emitting element 210b may be a green light-emitting element, and light-emitting element 210c may be a blue light-emitting element.

[0271] In photolithography, the finer the pattern to be processed, the more significant the effect of light diffraction becomes. This reduces the fidelity of the photomask pattern when it is transferred by exposure, making it difficult to process the resist mask into the desired shape. Therefore, even if the photomask pattern is rectangular, it is likely to have rounded corners. As a result, the top surface shape of the light-emitting element may be polygonal with rounded corners, elliptical, circular, or the like.

[0272] Furthermore, in a method for manufacturing a display panel according to one embodiment of the present invention, the EL layer is processed into an island shape using a resist mask. The resist film formed on the EL layer needs to be cured at a temperature lower than the heat resistance temperature of the EL layer. Therefore, depending on the heat resistance temperature of the material for the EL layer and the curing temperature of the resist material, the resist film may not be cured sufficiently. A resist film that is not cured sufficiently may have a shape that deviates from the desired shape during processing. As a result, the top surface shape of the EL layer may become a polygon with rounded corners, an ellipse, a circle, or the like. For example, when a resist mask with a square top surface shape is formed, a resist mask with a circular top surface shape may be formed, resulting in a circular top surface shape of the EL layer.

[0273] In order to form the top surface of the EL layer into a desired shape, a technique for correcting a mask pattern in advance (OPC (Optical Proximity Correction) technique) may be used so that the design pattern and the transfer pattern coincide with each other. Specifically, the OPC technique adds a correction pattern to the corners of figures on the mask pattern.

[0274] This concludes the description of the pixel layout.

[0275] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0276] Embodiment 4 In this embodiment, another structural example of a display panel that can be applied to an electronic device according to one embodiment of the present invention will be described.

[0277] The display panel of this embodiment is a high-definition display panel, and is particularly suitable for use as a display unit for VR devices such as head-mounted displays and wearable devices that can be worn on the head, such as glasses-type AR devices. The display panel of this embodiment can have the configuration of the display device 10 shown in embodiment 1.

[0278] 11A is a perspective view of a display module 280. The display module 280 includes a display panel 200A and an FPC 290. The display panel 200A can have the same structure as the display device 10 described in Embodiment 1.

[0279] The display module 280 includes a substrate 291, a substrate 292, and a display portion 281. The display portion 281 is a region for displaying an image. The substrate 291 corresponds to the layer 20 described in Embodiment 1, and a layer 30 including a light-emitting element and the like are provided between the substrate 291 and the substrate 292. The substrate 292 can be a glass substrate or the like that has high transmittance for light emitted from the light-emitting element.

[0280] 11B is a perspective view schematically illustrating the configuration on the substrate 291 side. A circuit portion 282, a circuit portion 283 on the circuit portion 282, and a circuit portion 284 on the circuit portion 283 are stacked over the substrate 291. Here, the circuit portion 282 is provided with the circuit 21a described in Embodiment 1. The circuit portion 283 is provided with the circuit 21b described in Embodiment 1. The circuit portion 284 is provided with the pixel circuit PIX described in Embodiment 1.

[0281] Furthermore, a terminal portion 285 for connection to the FPC 290 is provided on the substrate 291. The terminal portion 285 and the circuit portion 282 are electrically connected by a wiring portion 286 made up of a plurality of wires.

[0282] The circuit section 284 has a plurality of periodically arranged pixels 284a. An enlarged view of one pixel 284a is shown on the right side of Fig. 11B. The pixel 284a has a light-emitting element 210R that emits red light, a light-emitting element 210G that emits green light, and a light-emitting element 210B that emits blue light.

[0283] The circuit portion 284 also has a plurality of pixel circuits PIX arranged periodically. Each pixel circuit PIX is a circuit that controls the light emission of three light-emitting devices included in one pixel 284a. One pixel circuit PIX may be configured to have three circuits that control the light emission of one light-emitting device. For example, the pixel circuit PIX may be configured to have at least one selection transistor, one current control transistor (drive transistor), and a capacitor element for each light-emitting device. In this case, a gate signal is input to the gate of the selection transistor, and a source signal is input to the source. This realizes an active matrix display panel.

[0284] The circuit portion 282 and the circuit portion 283 have circuits for driving the pixel circuits PIX. The FPC 290 functions as wiring for supplying video data, a power supply potential, and the like from the outside to the circuit portion 282. An IC may be mounted on the FPC 290.

[0285] The display module 280 can be configured such that both the circuit unit 283 and the circuit unit 282 are stacked below the circuit unit 284, thereby enabling the aperture ratio (effective display area ratio) of the display unit 281 to be extremely high. For example, the aperture ratio of the display unit 281 can be 40% or more and less than 100%, preferably 50% or more and 95% or less, and more preferably 60% or more and 95% or less. Furthermore, the pixels 284a can be arranged at an extremely high density, enabling the resolution of the display unit 281 to be extremely high. For example, it is preferable that the pixels 284a be arranged in the display unit 281 at a resolution of 2000 ppi or more, preferably 3000 ppi or more, more preferably 5000 ppi or more, and even more preferably 6000 ppi or more, and 20,000 ppi or less, or 30,000 ppi or less.

[0286] Because such a display module 280 has extremely high resolution, it can be suitably used in VR devices such as head-mounted displays, or in glasses-type AR devices. For example, even in a configuration in which the display unit of the display module 280 is viewed through lenses, the display module 280 has an extremely high-resolution display unit 281, so even when the display unit is enlarged with lenses, the pixels are not visible, allowing for a highly immersive display. Furthermore, the display module 280 is not limited to this, and can be suitably used in electronic devices with relatively small display units. For example, it can be suitably used in the display unit of a wearable electronic device such as a wristwatch.

[0287] 12 has a stacked structure of a transistor 310 having a channel formed in a substrate 301, a transistor 320A having a channel formed in a semiconductor layer containing metal oxide, and a transistor 320B. Note that the stacked structure shown in FIG. 12 is an example of the structure shown in FIG. 2A.

[0288] 11A and 11B , the transistor 310, the transistor 320A, and the transistor 320B correspond to the Si transistor provided in the layer 20, the first OS transistor provided in the layer 30a, and the second OS transistor provided in the layer 30b, respectively, which are described in Embodiment 1.

[0289] The transistor 310 and the transistor 320A can be used as transistors that form a driver circuit (gate driver, source driver) for driving a pixel circuit or a functional circuit, and the transistor 320B can be used as a transistor that forms a pixel circuit.

[0290] The transistor 310 is a transistor having a channel formation region in a substrate 301. A semiconductor substrate such as a single crystal silicon substrate can be used as the substrate 301. Note that although a planar transistor is illustrated as an example of the transistor 310 in FIG. 12, a fin transistor may also be used.

[0291] The transistor 310 includes a part of a substrate 301, a conductive layer 311, a low-resistance region 312, an insulating layer 313, and an insulating layer 314. The conductive layer 311 functions as a gate electrode. The insulating layer 313 is located between the substrate 301 and the conductive layer 311 and functions as a gate insulating layer. The low-resistance region 312 is a region in which the substrate 301 is doped with impurities and functions as either a source or a drain. The insulating layer 314 is provided to cover a side surface of the conductive layer 311.

[0292] An element isolation layer 315 is provided between two adjacent transistors 310 so as to be embedded in the substrate 301 .

[0293] An insulating layer 261 is provided to cover the transistor 310, and a conductive layer 251 and a conductive layer 252 are provided over the insulating layer 261. An insulating layer 262 is provided to cover the conductive layers 251 and 252. The conductive layers 251 and 252 function as wirings. An insulating layer 332 is provided over the insulating layer 262, and a transistor 320A is provided over the insulating layer 332.

[0294] The insulating layer 332 functions as a barrier layer that prevents impurities such as water or hydrogen from diffusing into the transistor 320A from the substrate 301. For example, the insulating layer 332 can be a film through which hydrogen or oxygen diffuses less easily than a silicon oxide film, such as an aluminum oxide film, a hafnium oxide film, or a silicon nitride film.

[0295] The transistor 320A is a vertical transistor, and the description of the first OS transistor in Embodiment 1 can be referred to for details.

[0296] The transistor 320A is electrically connected to the transistor 310 via a plug 272, a conductive layer 251, and a plug 271. An insulating layer 333, an insulating layer 335, an insulating layer 336, a plug 275 electrically connected to the transistor 320A, a conductive layer 253 electrically connected to the plug 275, and the like can be provided over the transistor 320A as needed.

[0297] An insulating layer 334 is provided over the transistor 320A, and the transistor 320B is provided over the insulating layer 334. The insulating layer 334 can be formed using an insulating film similar to that of the insulating layer 332.

[0298] The transistor 320B is a transistor in which a metal oxide (also referred to as an oxide semiconductor) is used for a semiconductor layer in which a channel is formed, and corresponds to the second OS transistor described in Embodiment 1. The transistor 320B corresponds to the transistor M2 or M6 which is a driving transistor in the pixel circuit illustrated in FIG. 6A or 6B.

[0299] The transistor 320B includes a semiconductor layer 321 , an insulating layer 323 , a conductive layer 324 , a pair of conductive layers 325 , an insulating layer 326 , and a conductive layer 327 .

[0300] A conductive layer 327 is provided over the insulating layer 334, and an insulating layer 326 is provided to cover the conductive layer 327. The conductive layer 327 functions as a first gate electrode of the transistor 320B, and part of the insulating layer 326 functions as a first gate insulating layer. An oxide insulating film such as a silicon oxide film is preferably used for at least a portion of the insulating layer 326 that is in contact with the semiconductor layer 321. The top surface of the insulating layer 326 is preferably planarized.

[0301] The semiconductor layer 321 is provided over the insulating layer 326. The semiconductor layer 321 preferably includes a metal oxide (also referred to as an oxide semiconductor) film exhibiting semiconductor characteristics. A pair of conductive layers 325 is provided on and in contact with the semiconductor layer 321 and functions as a source electrode and a drain electrode.

[0302] An insulating layer 328 is provided to cover top surfaces and side surfaces of the pair of conductive layers 325 and side surfaces of the semiconductor layer 321, and an insulating layer 264 is provided over the insulating layer 328. The insulating layer 328 functions as a barrier layer that prevents impurities such as water or hydrogen from diffusing from the insulating layer 264 or the like into the semiconductor layer 321 and prevents oxygen from being released from the semiconductor layer 321. The insulating layer 328 can be an insulating film similar to the insulating layer 332.

[0303] An opening reaching the semiconductor layer 321 is provided in the insulating layer 328 and the insulating layer 264. An insulating layer 323 in contact with the top surface of the semiconductor layer 321 and a conductive layer 324 are buried in the opening. The conductive layer 324 functions as a second gate electrode, and the insulating layer 323 functions as a second gate insulating layer.

[0304] The upper surfaces of the conductive layer 324, the insulating layer 323, and the insulating layer 264 are planarized so that their heights are the same or approximately the same, and insulating layers 329 and 265 are provided to cover them.

[0305] The insulating layer 264 and the insulating layer 265 function as interlayer insulating layers. The insulating layer 329 functions as a barrier layer that prevents impurities such as water or hydrogen from diffusing from the insulating layer 265 or the like to the transistor 320B. The insulating layer 329 can be formed using an insulating film similar to the insulating layer 332.

[0306] A plug 274 electrically connected to one of the pair of conductive layers 325 is provided so as to be embedded in the insulating layer 265, the insulating layer 329, and the insulating layer 264. Here, the plug 274 preferably has a first conductive layer covering the side surfaces of the openings of the insulating layer 265, the insulating layer 329, the insulating layer 264, and the insulating layer 328 and a part of the upper surface of the conductive layer 325, and a second conductive layer in contact with the upper surface of the first conductive layer. In this case, it is preferable to use a conductive material through which hydrogen and oxygen do not easily diffuse as the first conductive layer.

[0307] The transistor 320B may have a structure such as a planar transistor, a staggered transistor, an inverted staggered transistor, a trench transistor, a fin transistor, or the like. The transistor may have either a top-gate or bottom-gate structure.

[0308] The transistor 320B has a structure in which a semiconductor layer in which a channel is formed is sandwiched between two gates. The two gates may be connected and the transistor may be driven by supplying the same signal to them. Alternatively, the threshold voltage of the transistor may be controlled by applying a potential for controlling the threshold voltage to one of the two gates and a potential for driving to the other.

[0309] The crystallinity of the semiconductor material used for the semiconductor layer of the transistor 320B is not particularly limited, and any of an amorphous semiconductor, a single crystal 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. The use of a single crystal semiconductor or a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0310] The band gap of the metal oxide used for the semiconductor layer of the transistor 320B is preferably 2 eV or more, more preferably 2.5 eV or more. The use of a metal oxide with a wide band gap can reduce the off-state current of the OS transistor. Note that the transistor 320B (second OS transistor) can be formed using a metal oxide similar to the metal oxide that can be used for the first OS transistor described in Embodiment 2.

[0311] An OS transistor has significantly higher field-effect mobility than a transistor using amorphous silicon. Furthermore, an OS transistor has significantly lower source-drain leakage current in an off state (hereinafter also referred to as off-state current), and can retain 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 display panel.

[0312] Furthermore, to increase the emission luminance of a light-emitting device included in a pixel circuit, it is necessary to increase the amount of current flowing through the light-emitting device. 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 source-drain withstand voltage 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 device and increase the emission luminance of the light-emitting device.

[0313] Furthermore, when a transistor operates in the saturation region, the change in source-drain current of an OS transistor is smaller than that of a Si transistor in response to a change in gate-source voltage. 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 through the light-emitting device. This allows for a larger gradation in the pixel circuit.

[0314] Furthermore, in terms of the saturation characteristics of the current that flows when a transistor operates in the 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 through a light-emitting device, even when the current-voltage characteristics of an EL device vary. In other words, when an OS transistor operates in the saturation region, the source-drain current of the OS transistor remains almost unchanged even when the source-drain voltage increases, thereby stabilizing the light-emitting luminance of the light-emitting device.

[0315] As described above, by using an OS transistor for a driving transistor included in a pixel circuit, it is possible to achieve "reduced power consumption," "increased light emission luminance," "multiple gray levels," "suppressed variations in light-emitting devices," and the like.

[0316] An insulating layer 265 is provided over the insulating layer 329, and a capacitor 240 is provided over the insulating layer 265. The capacitor 240 and the transistor 320B are electrically connected by a plug 274. The capacitor 240 corresponds to the transistor capacitor C1 or the capacitor C2 shown in FIGS.

[0317] The capacitor 240 has a conductive layer 241, a conductive layer 245, and an insulating layer 243 located therebetween. The conductive layer 241 functions as one electrode of the capacitor 240, the conductive layer 245 functions as the other electrode of the capacitor 240, and the insulating layer 243 functions as a dielectric of the capacitor 240.

[0318] The conductive layer 241 is provided over the insulating layer 265 and is buried in the insulating layer 254. The conductive layer 241 is electrically connected to one of the source and drain of the transistor 320B by a plug 256 buried in the insulating layer 255a. The insulating layer 243 is provided to cover the conductive layer 241. The conductive layer 245 is provided in a region overlapping with the conductive layer 241 with the insulating layer 243 interposed therebetween.

[0319] An insulating layer 255a is provided to cover the capacitor 240, an insulating layer 255b is provided over the insulating layer 255a, and an insulating layer 255c is provided over the insulating layer 255b.

[0320] An inorganic insulating film can be preferably used for each of the insulating layers 255a, 255b, and 255c. For example, it is preferable to use a silicon oxide film for the insulating layer 255a and the insulating layer 255c, and a silicon nitride film for the insulating layer 255b. This allows the insulating layer 255b to function as an etching protection film. In this embodiment, an example is shown in which part of the insulating layer 255c is etched to form a recess, but the insulating layer 255c does not necessarily have to have a recess.

[0321] The light-emitting elements 210R, 210G, and 210B are provided over the insulating layer 255c. Embodiment 3 can be referred to for the structures of the light-emitting elements 210R, 210G, and 210B.

[0322] The display panel 200A has a separate light-emitting device for each emitted color, so there is little change in chromaticity between light emitted at low and high luminance. Furthermore, because the organic layers 212R, 212G, and 212B are spaced apart from one another, crosstalk between adjacent subpixels can be suppressed even in a high-resolution display panel. This makes it possible to realize a high-resolution display panel with high display quality.

[0323] In the region between adjacent light emitting elements, an insulating layer 225, a resin layer 226, and a layer 228 are provided.

[0324] The pixel electrodes 211R, 211G, and 211B of the light-emitting element are electrically connected to one of the source and drain of the transistor 320B via a plug 256 embedded in the insulating layers 255a, 255b, and 255c, a conductive layer 241 embedded in the insulating layer 254, and a plug 274 embedded in the insulating layer 265. The height of the top surface of the insulating layer 255c and the height of the top surface of the plug 256 are the same or approximately the same. Various conductive materials can be used for the plug.

[0325] In addition, a protective layer 221 is provided on light emitting elements 210R, 210G, and 210B. A substrate 270 is attached to protective layer 221 with an adhesive layer 276. Substrate 270 corresponds to substrate 292 in FIG. 11A.

[0326] No insulating layer covering the upper end of each pixel electrode 211 is provided between two adjacent pixel electrodes 211. This allows the distance between adjacent light-emitting elements to be extremely narrow, resulting in a high-definition or high-resolution display panel.

[0327] In the above description, the first OS transistor is formed over the Si transistor with an insulating layer interposed therebetween and the two are electrically connected to each other through a plug. However, the Si transistor and the first OS transistor may be electrically connected to each other by bonding.

[0328] 13 illustrates a structure in which a transistor 310 (a Si transistor) and a transistor 320A (a first OS transistor) formed over a substrate 301 are electrically connected by bonding. Note that a description of the structure of layers above the transistor 320A will be omitted.

[0329] The transistor 320A is formed using a silicon substrate 302 as a support substrate. An insulating layer 266 is formed on a first surface of the silicon substrate 302, and a conductive layer 258 is provided on the insulating layer 266. One of the source or drain of the transistor 320A is electrically connected to the conductive layer 258 via a plug 272 embedded in an insulating layer 262 and an insulating layer 332 provided on the insulating layer 266 and the conductive layer 258.

[0330] Moreover, an insulating layer 267 is formed on a second surface of the silicon substrate 302 opposite to the first surface, and an insulating layer 268 and a conductive layer 259 are provided on the insulating layer 267. Here, the insulating layer 268 and the conductive layer 259 also function as bonding layers, and the conductive layer 259 has a region buried in the insulating layer 268, and the top surfaces of both are flattened.

[0331] Furthermore, a through hole is formed in the silicon substrate 302, and the conductive layer 258 and the conductive layer 259 are electrically connected by a through electrode 257 formed in the through hole via an insulating layer.

[0332] An insulating layer 261 is provided over the transistor 310 provided over the substrate 301, and an insulating layer 269 and a conductive layer 251 are provided over the insulating layer 261. Here, the insulating layer 269 and the conductive layer 251 also function as bonding layers, the conductive layer 251 has a region buried in the insulating layer 269, and the top surfaces of both are planarized.

[0333] Bonding can be achieved by bringing the surfaces of the insulating layer 268 and the insulating layer 269 into contact with each other, and the surfaces of the conductive layer 259 and the conductive layer 251 into contact with each other. Thus, the transistor 310 and the transistor 320A can be electrically connected by being attached to each other.

[0334] Note that insulating layer 268 and insulating layer 269 are preferably inorganic insulating layers formed of the same material. Furthermore, it is preferable to use the same conductive material for conductive layer 259 and conductive layer 251. For example, a metal film containing an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W, or a metal nitride film containing the above-mentioned elements (titanium nitride film, molybdenum nitride film, tungsten nitride film), etc., can be used. In particular, copper is preferably used for conductive layer 259 and conductive layer 251 because of its ease of bonding.

[0335] Although the transistor 320A is used as a transistor included in a driver circuit or a functional circuit in the above example, the transistor 320A can also be used as a transistor included in a pixel circuit.

[0336] 14 shows an example in which the transistor 320A is used as a selection transistor in a pixel circuit. Since it is preferable for the selection transistor of the pixel circuit to be capable of high-speed driving, it may be configured as a vertical transistor with a high on-state current. On the other hand, since it is preferable for the drive transistor to have good saturation characteristics, it is preferable to use a transistor with a relatively long channel length. Therefore, it is preferable to provide the drive transistor as a transistor whose channel length can be determined in a lithography process.

[0337] Here, if the transistor 320B has a configuration in which the front gate and the back gate are electrically connected, similar to the transistor M2 (driving transistor) shown in Figure 6B, one of the source or drain of the transistor 320A can be electrically connected to the conductive layer 327, which is the back gate of the transistor 320B.

[0338] That is, one of the source and drain of the transistor 320A and the gate of the transistor 320B can be electrically connected with a simpler structure than a structure in which the gate of the transistor 320A is formed only by the conductive layer 324 (without a back gate).

[0339] Note that while Figure 14 shows a configuration in which transistors 320A and 320B are electrically connected via plug 275, conductive layer 253, and plug 273, transistors 320A and 320B may be electrically connected by only one of plug 275 or plug 273.

[0340] Although FIG. 14 does not show the transistor 320A as an element of the driving circuit, the transistor 320A can be used as an element of both the pixel circuit and the driving circuit by using the configuration shown in FIG. 2B or FIG. 2C.

[0341] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0342] Embodiment 5 In this embodiment, a light-emitting device (light-emitting element) that can be used for a display panel of one embodiment of the present invention will be described.

[0343] 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.

[0344] In this specification, a structure in which at least light-emitting layers are separately fabricated for light-emitting devices with different emission wavelengths may be referred to as an SBS (Side By Side) structure. The SBS structure allows the materials and configuration to be optimized for each light-emitting device, increasing the freedom in material and configuration selection and facilitating improvements in brightness and reliability.

[0345] 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 from each other depending on their cross-sectional shapes or characteristics. Furthermore, one layer may have two or three functions among the carrier injection layer, carrier transport layer, and carrier block layer.

[0346] In this specification and the like, a light-emitting device (also referred to as a light-emitting element) has an EL layer between a pair of electrodes. The EL layer has at least a light-emitting layer. Here, 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).

[0347] As the light-emitting device, for example, an OLED (organic light-emitting diode) or a QLED (quantum-dot light-emitting diode) is preferably used. Examples of the light-emitting material contained in the light-emitting device include a fluorescent material (fluorescent material), a phosphorescent material (phosphorescent material), a material that exhibits thermally activated delayed fluorescence (thermally activated delayed fluorescence: TADF material), and an inorganic compound (quantum dot material, etc.). Furthermore, an LED such as a micro LED can also be used as the light-emitting device.

[0348] The light emitting device can emit light of infrared, red, green, blue, cyan, magenta, yellow, white, etc. The color purity can be improved by providing the light emitting device with a microcavity structure.

[0349] 15A, the light-emitting device has an EL layer 763 between a pair of electrodes (a lower electrode 761 and an upper electrode 762). The EL layer 763 can be composed of multiple layers, such as a layer 780, a light-emitting layer 771, and a layer 790.

[0350] The light-emitting layer 771 contains at least a light-emitting substance (also referred to as a light-emitting material).

[0351] When the lower electrode 761 is an anode and the upper electrode 762 is a cathode, the layer 780 includes one or more of a layer containing a substance with high hole-injecting properties (hole-injecting layer), a layer containing a substance with high hole-transporting properties (hole-transporting layer), and a layer containing a substance with high electron-blocking properties (electron-blocking layer). The layer 790 also includes one or more of a layer containing a substance with high electron-injecting properties (electron-injecting layer), a layer containing a substance with high electron-transporting properties (electron-transporting layer), and a layer containing a substance with high hole-blocking properties (hole-blocking layer). When the lower electrode 761 is a cathode and the upper electrode 762 is an anode, the layers 780 and 790 have the opposite structures to those described above.

[0352] A structure including the layer 780, the light-emitting layer 771, and the layer 790 provided between a pair of electrodes can function as a single light-emitting unit, and the structure of FIG. 15A is referred to as a single structure in this specification.

[0353] 15B shows a modified example of the EL layer 763 included in the light-emitting device shown in Fig. 15A. Specifically, the light-emitting device shown in Fig. 15B includes a layer 781 on a lower electrode 761, a layer 782 on the layer 781, a light-emitting layer 771 on the layer 782, a layer 791 on the light-emitting layer 771, a layer 792 on the layer 791, and an upper electrode 762 on the layer 792.

[0354] When the lower electrode 761 is an anode and the upper electrode 762 is a cathode, for example, the layer 781 can be a hole injection layer, the layer 782 can be a hole transport layer, the layer 791 can be an electron transport layer, and the layer 792 can be an electron injection layer. When the lower electrode 761 is a cathode and the upper electrode 762 is an anode, the layer 781 can be an electron injection layer, the layer 782 can be an electron transport layer, the layer 791 can be a hole transport layer, and the layer 792 can be a hole injection layer. Such a layer structure allows carriers to be efficiently injected into the light-emitting layer 771, and the efficiency of carrier recombination in the light-emitting layer 771 can be increased.

[0355] 15C and 15D, a variation of the single structure is a configuration in which multiple light-emitting layers (light-emitting layers 771, 772, and 773) are provided between layer 780 and layer 790. While FIGS. 15C and 15D show an example having three light-emitting layers, the number of light-emitting layers in a single-structure light-emitting device may be two, four, or more. Furthermore, a single-structure light-emitting device may have a buffer layer between the two light-emitting layers.

[0356] 15E and 15F, a configuration in which a plurality of light-emitting units (light-emitting unit 763a and light-emitting unit 763b) are connected in series via a charge generation layer 785 (also referred to as an intermediate layer) is referred to as a tandem structure in this specification. The tandem structure may also be referred to as a stack structure. The tandem structure can provide a light-emitting device capable of emitting high-luminance light. Furthermore, the tandem structure can reduce the current required to obtain the same luminance compared to a single structure, thereby improving reliability.

[0357] 15D and 15F are examples in which the display panel has a layer 764 that overlaps with the light-emitting device. Fig. 15D is an example in which the layer 764 overlaps with the light-emitting device shown in Fig. 15C, and Fig. 15F is an example in which the layer 764 overlaps with the light-emitting device shown in Fig. 15E.

[0358] The layer 764 can be a color conversion layer, a color filter (coloring layer), or both.

[0359] 15C and 15D , light-emitting layers 771, 772, and 773 may be made of light-emitting materials that emit light of the same color, or even the same light-emitting material. For example, light-emitting layers 771, 772, and 773 may be made of a light-emitting material that emits blue light. In the subpixel that emits blue light, blue light emitted by the light-emitting device can be extracted. Furthermore, in the subpixels that emit red light and the subpixels that emit green light, a color conversion layer can be provided as layer 764 shown in FIG. 15D to convert blue light emitted by the light-emitting device into light with a longer wavelength, thereby allowing red or green light to be extracted.

[0360] Furthermore, light-emitting materials with different emission colors may be used for the light-emitting layers 771, 772, and 773. When the lights emitted by the light-emitting layers 771, 772, and 773 are complementary in color, white light can be obtained. For example, a light-emitting device with a single structure preferably has a light-emitting layer containing a light-emitting material that emits blue light and a light-emitting layer containing a light-emitting material that emits visible light with a wavelength longer than blue.

[0361] For example, when a light-emitting device with a single structure has three light-emitting layers, it preferably has a light-emitting layer containing a light-emitting material that emits red (R) light, a light-emitting layer containing a light-emitting material that emits green (G) light, and a light-emitting layer containing a light-emitting material that emits blue (B) light. The stacking order of the light-emitting layers can be R, G, B from the anode side, or R, B, G from the anode side, etc. In this case, a buffer layer may be provided between R and G or B.

[0362] For example, when a light-emitting device with a single structure has two light-emitting layers, it is preferable that the light-emitting layer has a light-emitting substance that emits blue (B) light and the light-emitting layer has a light-emitting substance that emits yellow light. This structure is sometimes called a BY single.

[0363] 15D, a color filter may be provided as the layer 764. When white light passes through the color filter, light of a desired color can be obtained.

[0364] A light-emitting device that emits white light preferably contains two or more types of light-emitting materials. To obtain white light emission, light-emitting materials can be selected so that the light emitted from each of the two or more light-emitting materials has 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 complementary to each other, a light-emitting device that emits white light as a whole can be obtained. The same applies to a light-emitting device having three or more light-emitting layers.

[0365] 15E and 15F, the light-emitting layer 771 and the light-emitting layer 772 may be made of a light-emitting material that emits light of the same color, or even the same light-emitting material.

[0366] For example, in the light-emitting devices included in the subpixels emitting light of each color, light-emitting materials emitting blue light may be used for the light-emitting layers 771 and 772. In the subpixel emitting blue light, the blue light emitted by the light-emitting device can be extracted. In the subpixel emitting red light and the subpixel emitting green light, a color conversion layer is provided as the layer 764 shown in FIG. 15F to convert the blue light emitted by the light-emitting device into light with a longer wavelength, thereby allowing red or green light to be extracted.

[0367] Furthermore, when the light-emitting devices having the configurations shown in FIG. 15E or 15F are used for the subpixels emitting light of each color, different light-emitting materials may be used for each subpixel. Specifically, in a light-emitting device included in a subpixel emitting red light, light-emitting materials that emit red light may be used for the light-emitting layers 771 and 772, respectively. Similarly, in a light-emitting device included in a subpixel emitting green light, light-emitting materials that emit green light may be used for the light-emitting layers 771 and 772, respectively. In a light-emitting device included in a subpixel emitting blue light, light-emitting materials that emit blue light may be used for the light-emitting layers 771 and 772, respectively. A display panel having such a configuration can be said to employ a tandem-structure light-emitting device and also have an SBS structure. Therefore, it can have the advantages of both the tandem structure and the SBS structure. This allows for a highly reliable light-emitting device to be realized.

[0368] 15E and 15F, light-emitting layers 771 and 772 may be made of light-emitting materials that emit light of different colors. When the light emitted by light-emitting layer 771 and the light emitted by light-emitting layer 772 are complementary colors, white light can be obtained. A color filter may be provided as layer 764 shown in FIG. 15F. When white light passes through the color filter, light of a desired color can be obtained.

[0369] 15E and 15F show an example in which the light-emitting unit 763a has one light-emitting layer 771 and the light-emitting unit 763b has one light-emitting layer 772, but this is not limiting. Each of the light-emitting unit 763a and the light-emitting unit 763b may have two or more light-emitting layers.

[0370] 15E and 15F show examples of light emitting devices having two light emitting units, but the present invention is not limited to this. The light emitting device may have three or more light emitting units.

[0371] Specifically, the light-emitting device configurations shown in FIGS. 16A to 16C can be given.

[0372] 16A shows a configuration having three light-emitting units. Note that a configuration having two light-emitting units may be called a two-stage tandem structure, and a configuration having three light-emitting units may be called a three-stage tandem structure.

[0373] 16A , a plurality of light-emitting units (light-emitting unit 763a, light-emitting unit 763b, and light-emitting unit 763c) are connected in series via charge generation layer 785. Light-emitting unit 763a includes layer 780a, light-emitting layer 771, and layer 790a, light-emitting unit 763b includes layer 780b, light-emitting layer 772, and layer 790b, and light-emitting unit 763c includes layer 780c, light-emitting layer 773, and layer 790c.

[0374] 16A , it is preferable that the light-emitting layers 771, 772, and 773 each contain a light-emitting material that emits light of the same color. Specifically, the light-emitting layers 771, 772, and 773 may each contain a red (R) light-emitting material (a so-called R\R\R three-stage tandem structure), the light-emitting layers 771, 772, and 773 may each contain a green (G) light-emitting material (a so-called G\G\G three-stage tandem structure), or the light-emitting layers 771, 772, and 773 may each contain a blue (B) light-emitting material (a so-called B\B\B three-stage tandem structure).

[0375] Note that the light-emitting materials that emit light of the same color are not limited to the above configuration. For example, as shown in FIG. 16B , a tandem light-emitting device may be used in which light-emitting units having multiple light-emitting materials are stacked. FIG. 16B shows a configuration in which multiple light-emitting units (light-emitting unit 763a and light-emitting unit 763b) are connected in series via charge generation layer 785. Furthermore, light-emitting unit 763a includes layer 780a, light-emitting layer 771a, light-emitting layer 771b, light-emitting layer 771c, and layer 790a. Light-emitting unit 763b includes layer 780b, light-emitting layer 772a, light-emitting layer 772b, light-emitting layer 772c, and layer 790b.

[0376] In the structure shown in FIG. 16B , light-emitting layers 771a, 771b, and 771c are configured to emit white light (W) by selecting light-emitting materials with complementary colors. Light-emitting layers 772a, 772b, and 772c are configured to emit white light (W) by selecting light-emitting materials with complementary colors. That is, the structure shown in FIG. 16C has a two-tiered W / W tandem structure. Note that the stacking order of the light-emitting materials with complementary colors for light-emitting layers 771a, 771b, and 771c is not particularly limited. The implementer can select the optimal stacking order as appropriate. Although not shown, a three-tiered W / W / W tandem structure or a four-tiered or more tandem structure may also be used.

[0377] In addition, when a light-emitting device having a tandem structure is used, there are a B\Y two-stage tandem structure having a light-emitting unit that emits yellow (Y) light and a light-emitting unit that emits blue (B) light, a R·G\B two-stage tandem structure having a light-emitting unit that emits red (R) and green (G) light and a light-emitting unit that emits blue (B) light, a light-emitting unit that emits yellow (Y) light and a light-emitting unit that emits blue (B) light, and a light-emitting unit that emits blue (B) light. Examples of such a tandem structure include a B\Y\B three-stage tandem structure having, in this order, a light-emitting unit that emits blue (B) light, a light-emitting unit that emits yellow-green (YG) light, and a light-emitting unit that emits blue (B) light, and a B\G\B three-stage tandem structure having, in this order, a light-emitting unit that emits blue (B) light, a light-emitting unit that emits green (G) light, and a light-emitting unit that emits blue (B) light.

[0378] Furthermore, as shown in FIG. 16C, a light-emitting unit having one light-emitting substance and a light-emitting unit having a plurality of light-emitting substances may be combined.

[0379] 16C , a plurality of light-emitting units (light-emitting unit 763a, light-emitting unit 763b, and light-emitting unit 763c) are connected in series via charge generation layer 785. Light-emitting unit 763a includes layer 780a, light-emitting layer 771, and layer 790a, light-emitting unit 763b includes layer 780b, light-emitting layer 772a, light-emitting layer 772b, light-emitting layer 772c, and layer 790b, and light-emitting unit 763c includes layer 780c, light-emitting layer 773, and layer 790c.

[0380] For example, in the configuration shown in Figure 16C, a three-stage tandem structure of B\R·G·YG\B can be applied, in which light-emitting unit 763a is a light-emitting unit that emits blue (B) light, light-emitting unit 763b is a light-emitting unit that emits red (R), green (G), and yellow-green (YG) light, and light-emitting unit 763c is a light-emitting unit that emits blue (B) light.

[0381] 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.

[0382] 15C and 15D, the layer 780 and the layer 790 may each independently have a laminated structure made up of two or more layers, as shown in FIG. 15B.

[0383] 15E and 15F, light-emitting unit 763a includes layer 780a, light-emitting layer 771, and layer 790a, and light-emitting unit 763b includes layer 780b, light-emitting layer 772, and layer 790b.

[0384] When the lower electrode 761 is an anode and the upper electrode 762 is a cathode, the layers 780a and 780b each have one or more of a hole injection layer, a hole transport layer, and an electron blocking layer. The layers 790a and 790b each have one or more of an electron injection layer, an electron transport layer, and a hole blocking layer. When the lower electrode 761 is a cathode and the upper electrode 762 is an anode, the layers 780a and 790a have the opposite structures to those described above, and the layers 780b and 790b also have the opposite structures to those described above.

[0385] When the lower electrode 761 is an anode and the upper electrode 762 is a cathode, for example, the layer 780a may have a hole injection layer, a hole transport layer on the hole injection layer, and an electron blocking layer on the hole transport layer. The layer 790a may have an electron transport layer and a hole blocking layer between the light-emitting layer 771 and the electron transport layer. The layer 780b may have a hole transport layer and an electron blocking layer on the hole transport layer. The layer 790b may have an electron transport layer, an electron injection layer on the electron transport layer, and a hole blocking layer between the light-emitting layer 772 and the electron transport layer. When the lower electrode 761 is a cathode and the upper electrode 762 is an anode, for example, the layer 780a may have an electron injection layer, an electron transport layer on the electron injection layer, and an electron blocking layer on the electron transport layer. Layer 790a has a hole transport layer and may further have an electron blocking layer between light-emitting layer 771 and the hole transport layer. Layer 780b has an electron transport layer and may further have a hole blocking layer on the electron transport layer. Layer 790b has a hole transport layer and a hole injection layer on the hole transport layer and may further have an electron blocking layer between light-emitting layer 772 and the hole transport layer.

[0386] When a light-emitting device having a tandem structure is fabricated, two light-emitting units are stacked via a charge generation layer 785. The charge generation layer 785 has at least a charge generation region. The charge generation layer 785 has a function of injecting electrons into one of the two light-emitting units and injecting holes into the other when a voltage is applied between a pair of electrodes.

[0387] Next, materials that can be used in light-emitting devices will be described.

[0388] Of the lower electrode 761 and the upper electrode 762, a conductive film that transmits visible light is used for the electrode from which light is extracted. It is preferable to use a conductive film that reflects visible light for the electrode from which light is not extracted. When the display panel has a light-emitting device that emits infrared light, it is preferable to use a conductive film that transmits visible light and infrared light for the electrode from which light is extracted, and a conductive film that reflects visible light and infrared light for the electrode from which light is not extracted.

[0389] 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, the electrode is preferably disposed between the reflective layer and the EL layer 763. That is, light emitted from the EL layer 763 may be reflected by the reflective layer and extracted from the display panel.

[0390] Materials for forming the pair of electrodes of a light-emitting device can include metals, alloys, electrically conductive compounds, and mixtures thereof. Specific examples of such materials include metals such as aluminum, 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 alloys, such as an aluminum-nickel-lanthanum alloy (Al-Ni-La), 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.

[0391] A microresonator (microcavity) structure is preferably applied to the light-emitting device. Therefore, one of a pair of electrodes of the light-emitting device is preferably an electrode that is transparent and reflective to visible light (semi-transmissive / semi-reflective electrode), and the other is preferably an electrode that is reflective to visible light (reflective electrode). By having the light-emitting device have a microcavity structure, light emitted from the light-emitting layer can be resonated between the two electrodes, thereby intensifying the light emitted from the light-emitting device.

[0392] The semi-transmitting / semi-reflective electrode can have a stacked structure of a conductive layer that can be used as a reflective electrode and a conductive layer that can be used as an electrode that is transparent to visible light (also referred to as a transparent electrode).

[0393] 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 a light-emitting device. 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. The resistivity of these electrodes is 1×10 −２ Preferably, it is Ωcm or less.

[0394] The light-emitting device has at least a light-emitting layer. The light-emitting device may further include a layer other than the light-emitting layer, which layer contains a substance with high hole-injection properties, a substance with high hole-transport properties, a hole-blocking material, a substance with high electron-transport properties, an electron-blocking material, a substance with high electron-injection properties, or a bipolar substance (a substance with high electron-transport properties and high hole-transport properties). For example, the light-emitting device may have, in addition to the light-emitting layer, one or more layers selected from a hole-injection layer, a hole-transport layer, a hole-blocking layer, a charge-generating layer, an electron-blocking layer, an electron-transport layer, and an electron-injection layer.

[0395] The light-emitting device 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 device can be formed by a method such as vapor deposition (including vacuum vapor deposition), transfer, printing, inkjet printing, or coating.

[0396] The light-emitting layer contains one or more light-emitting materials. As the light-emitting material, a material that emits light of blue, purple, blue-purple, green, yellow-green, yellow, orange, red, or the like is appropriately used. Furthermore, a material that emits near-infrared light can also be used as the light-emitting material.

[0397] The light-emitting material may include a fluorescent material, a phosphorescent material, a TADF material, and a quantum dot material.

[0398] Examples of fluorescent materials include pyrene derivatives, anthracene derivatives, triphenylene derivatives, fluorene derivatives, carbazole derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, dibenzoquinoxaline derivatives, quinoxaline derivatives, pyridine derivatives, pyrimidine derivatives, phenanthrene derivatives, and naphthalene derivatives.

[0399] Examples of phosphorescent materials include organometallic complexes (particularly iridium complexes) having a 4H-triazole skeleton, a 1H-triazole skeleton, an imidazole skeleton, a pyrimidine skeleton, a pyrazine skeleton, or a pyridine skeleton; organometallic complexes (particularly iridium complexes) having a phenylpyridine derivative having an electron-withdrawing group as a ligand; platinum complexes; and rare earth metal complexes.

[0400] The light-emitting layer may contain one or more organic compounds (host material, assist material, etc.) in addition to the 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. As the hole-transporting material, a material with high hole transport properties that can be used in the hole-transporting layer, which will be described later, can be used. As the electron-transporting material, a material with high electron transport properties that can be used in the electron-transporting layer, which will be described later, can be used. Furthermore, as the one or more organic compounds, a bipolar material or a TADF material may be used.

[0401] The light-emitting layer preferably includes, for example, a phosphorescent material and a hole-transporting material and an electron-transporting material that are a combination that easily forms an exciplex. This configuration allows for 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 for efficient emission. This configuration simultaneously enables high efficiency, low-voltage operation, and long life of the light-emitting device.

[0402] The hole injection layer is a layer that injects holes from the anode into the hole transport layer and contains a material with high hole injection properties, such as an aromatic amine compound and a composite material containing a hole transport material and an acceptor material (electron acceptor material).

[0403] As the hole transporting material, a material having high hole transporting properties that can be used for the hole transport layer, which will be described later, can be used.

[0404] Examples of acceptable materials include oxides of metals belonging to Groups 4 to 8 of the periodic table. Specific examples include molybdenum oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, tungsten oxide, manganese oxide, and rhenium oxide. Among these, molybdenum oxide is particularly preferred because it is stable in the atmosphere, has low hygroscopicity, and is easy to handle. Also, organic acceptable materials containing fluorine can be used. Other acceptable materials include quinodimethane derivatives, chloranil derivatives, and hexaazatriphenylene derivatives.

[0405] For example, as a material with high hole injection properties, a material containing a hole transporting material and an oxide of a metal belonging to Groups 4 to 8 of the periodic table (typically, molybdenum oxide) may be used.

[0406] The hole transport layer is a layer that transports holes injected from the anode by the hole injection layer to the light emitting layer. The hole transport layer is a layer that contains a hole transport material. The hole transport material is a material having a concentration of 1×10 −６ cm ２ A substance having a hole mobility of 1 / Vs or more is preferred. Note that other substances can also be used as long as they have a higher hole transporting property than electron transporting property. As the hole transporting material, a material having a high hole transporting property, such as a π-electron-rich heteroaromatic compound (e.g., a carbazole derivative, a thiophene derivative, a furan derivative, etc.) or an aromatic amine (a compound having an aromatic amine skeleton), is preferred.

[0407] The electron blocking layer is provided in contact with the light-emitting layer. The electron blocking layer is a layer containing a material that has hole transport properties and can block electrons. The electron blocking layer can be made of a material that has electron blocking properties among the hole transport materials described above.

[0408] The electron blocking layer has hole transport properties and can therefore also be called a hole transport layer. Furthermore, a layer of the hole transport layer that has electron blocking properties can also be called an electron blocking layer.

[0409] The electron transport layer is a layer that transports electrons injected from the cathode by the electron injection layer to the light emitting layer. The electron transport layer is a layer that contains an electron transporting material. The electron transporting material is a material having a molecular weight of 1×10 −６ cm ２ A substance having an electron mobility of 1 / Vs or more is preferred. Note that other substances can also be used as long as they have a higher electron transporting property than holes. Examples of electron-transporting materials that can be used include metal complexes having a quinoline skeleton, metal complexes having a benzoquinoline skeleton, metal complexes having an oxazole skeleton, and metal complexes having a thiazole skeleton, as well as oxadiazole derivatives, triazole derivatives, imidazole derivatives, oxazole derivatives, thiazole derivatives, phenanthroline derivatives, quinoline derivatives having a quinoline ligand, benzoquinoline derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, and other π-electron-deficient heteroaromatic compounds including nitrogen-containing heteroaromatic compounds.

[0410] The hole-blocking layer is provided in contact with the light-emitting layer. The hole-blocking layer is a layer containing a material that has electron transport properties and can block holes. The hole-blocking layer can be made of a material that has hole-blocking properties and is selected from the above electron-transporting materials.

[0411] The hole blocking layer has electron transport properties and can therefore also be called an electron transport layer. Furthermore, a layer of the electron transport layer that has hole blocking properties can also be called a hole blocking layer.

[0412] The electron injection layer is a layer that injects electrons from the cathode to the electron transport layer and contains a material with high electron injection properties. Examples of the material with high electron injection properties include alkali metals, alkaline earth metals, and compounds thereof. Examples of the material with high electron injection properties include a composite material containing an electron transport material and a donor material (electron donor material).

[0413] Furthermore, it is preferable that the LUMO level of a material with high electron injection properties has a small difference (specifically, 0.5 eV or less) from the work function value of the material used for the cathode.

[0414] The electron injection layer may contain, for example, lithium, cesium, ytterbium, lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF ｘ , where X is an arbitrary number), 8-(quinolinolato)lithium (abbreviation: Liq), 2-(2-pyridyl)phenolatolithium (abbreviation: LiPP), 2-(2-pyridyl)-3-pyridinolatolithium (abbreviation: LiPPy), 4-phenyl-2-(2-pyridyl)phenolatolithium (abbreviation: LiPPP), lithium oxide (LiO ｘ ), alkali metals such as cesium carbonate, alkaline earth metals, or compounds thereof can be used. The electron injection layer may have a stacked structure of two or more layers. For example, the stacked structure may have a structure in which lithium fluoride is used as the first layer and ytterbium is provided as the second layer.

[0415] The electron injection layer may contain an electron transporting material. For example, a compound having an unshared electron pair and an electron-deficient heteroaromatic ring can be used as the electron transporting material. Specifically, a compound having at least one of a pyridine ring, a diazine ring (pyrimidine ring, pyrazine ring, pyridazine ring), and a triazine ring can be used.

[0416] The lowest unoccupied molecular orbital (LUMO) level of an organic compound having an unshared electron pair is preferably −3.6 eV or more and −2.3 eV or less. Generally, the highest occupied molecular orbital (HOMO) level and the LUMO level of an organic compound can be estimated by CV (cyclic voltammetry), photoelectron spectroscopy, optical absorption spectroscopy, inverse photoelectron spectroscopy, or the like.

[0417] For example, 4,7-diphenyl-1,10-phenanthroline (abbreviation: BPhen), 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), diquinoxalino[2,3-a:2′,3′-c]phenazine (abbreviation: HATNA), 2,4,6-tris[3′-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), etc. can be used as the organic compound having an unshared electron pair. Note that NBPhen has a higher glass transition point (Tg) and is superior in heat resistance compared to BPhen.

[0418] As described above, the charge generation layer has at least a charge generation region. The charge generation region preferably contains an acceptor material, for example, a hole transport material and an acceptor material applicable to the hole injection layer.

[0419] The charge generation layer preferably includes a layer containing a material with high electron injection properties. This layer may also be called an electron injection buffer layer. The electron injection buffer layer is preferably provided between the charge generation region and the electron transport layer. By providing the electron injection buffer layer, the injection barrier between the charge generation region and the electron transport layer can be alleviated, so that electrons generated in the charge generation region can be easily injected into the electron transport layer.

[0420] The electron injection buffer layer preferably contains an alkali metal or an alkaline earth metal, and may contain, for example, an alkali metal compound or an alkaline earth metal compound. Specifically, the electron injection buffer layer preferably contains an inorganic compound containing an alkali metal and oxygen, or an inorganic compound containing an alkaline earth metal and oxygen, and may contain an inorganic compound containing lithium and oxygen (lithium oxide (Li ２ In addition, the electron injection buffer layer can be suitably made of the materials applicable to the electron injection layer described above.

[0421] The charge generation layer preferably has a layer containing a material with high electron transport properties. This layer can also be called an electron relay layer. The electron relay layer is preferably provided between the charge generation region and the electron injection buffer layer. When the charge generation layer does not have an electron injection buffer layer, the electron relay layer is preferably provided between the charge generation region and the electron transport layer. The electron relay layer has the function of preventing interaction between the charge generation region and the electron injection buffer layer (or the electron transport layer) and smoothly transferring electrons.

[0422] For the electron relay layer, it is preferable to use a phthalocyanine-based material such as copper (II) phthalocyanine (abbreviated as CuPc) or a metal complex having a metal-oxygen bond and an aromatic ligand.

[0423] It should be noted that the charge generation region, electron injection buffer layer, and electron relay layer may not be clearly distinguishable from one another depending on their cross-sectional shapes or characteristics.

[0424] The charge generation layer may contain a donor material instead of an acceptor material. For example, the charge generation layer may contain a layer containing an electron transport material and a donor material that can be used for the electron injection layer.

[0425] When light-emitting units are stacked, an increase in driving voltage can be suppressed by providing a charge generating layer between two light-emitting units.

[0426] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0427] Embodiment 6 In this embodiment, electronic devices to which a display device according to one embodiment of the present invention can be applied will be described.

[0428] A display device according to one embodiment of the present invention can be applied to a display portion of an electronic device. Therefore, an electronic device with high display quality, extremely high resolution, or high reliability can be realized.

[0429] Examples of electronic devices using a display device according to one embodiment of the present invention include display devices such as televisions and monitors, lighting devices, desktop or notebook personal computers, word processors, and DVD (Digital Versatile Examples of such equipment include image playback devices that play back still images or videos stored on recording media such as a CD or DVD, portable CD players, radios, tape recorders, headphone stereos, stereos, table clocks, wall clocks, cordless telephone handsets, transceivers, car phones, mobile phones, personal digital assistants, tablet terminals, portable game machines, fixed game machines such as pachinko machines, calculators, electronic organizers, e-book terminals, electronic translators, voice input devices, video cameras, digital still cameras, electric shavers, high-frequency heating devices such as microwave ovens, air conditioning equipment such as electric rice cookers, electric washing machines, electric vacuum cleaners, hot water heaters, electric fans, hair dryers, air conditioners, humidifiers, and dehumidifiers, dishwashers, dish dryers, clothes dryers, futon dryers, electric refrigerators, electric freezers, electric refrigerator-freezers, DNA storage freezers, flashlights, tools such as chainsaws, smoke detectors, and medical equipment such as dialysis machines. Further examples include industrial equipment such as emergency lights, traffic lights, conveyor belts, elevators, escalators, industrial robots, power storage systems, and power storage devices for power leveling and smart grids. Mobile vehicles propelled by fuel-powered engines or electric motors powered by power from power storage devices may also be included in the category of electronic devices. Examples of such mobile vehicles include electric vehicles (EVs), hybrid vehicles (HVs) that combine internal combustion engines and electric motors, plug-in hybrid vehicles (PHVs), tracked vehicles in which the tires and wheels of these vehicles are replaced with tracks, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, golf carts, small or large ships, submarines, helicopters, aircraft, rockets, artificial satellites, space probes, planetary probes, and spaceships.

[0430] An electronic device according to one embodiment of the present invention may include a secondary battery (battery), and it is preferable that the secondary battery can be charged using contactless power transmission.

[0431] Examples of secondary batteries include lithium ion secondary batteries, nickel-metal hydride batteries, nickel-cadmium batteries, organic radical batteries, lead-acid batteries, air secondary batteries, nickel-zinc batteries, and silver-zinc batteries.

[0432] An electronic device according to one embodiment of the present invention may include an antenna. By receiving a signal through the antenna, images, information, and the like can be displayed on a display portion. When the electronic device includes an antenna and a secondary battery, the antenna may be used for contactless power transmission.

[0433] An electronic device according to one embodiment of the present invention may have a sensor (including the function of detecting, detecting or measuring force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor or infrared rays).

[0434] An electronic device according to one embodiment of the present invention can have various functions, such as a function to display various information (still images, videos, text images, etc.) on a display unit, a touch panel function, a function to display a calendar, date, time, etc., a function to execute various software (programs), a wireless communication function, a function to read programs or data recorded on a recording medium, etc.

[0435] Furthermore, electronic devices having multiple display units can have a function of mainly displaying image information on one part of the display units and mainly displaying text information on another part, or a function of displaying a stereoscopic image by displaying an image taking into account parallax on the multiple display units. Furthermore, electronic devices having an image receiving unit can have a function of capturing a still image or a video, a function of automatically or manually correcting the captured image, a function of storing the captured image in a recording medium (external or built in the electronic device), a function of displaying the captured image on the display unit, etc. Note that the functions of the electronic device of one embodiment of the present invention are not limited to these, and can have various functions.

[0436] A display device according to an embodiment of the present invention can display high-resolution images. Therefore, the display device can be particularly suitably used in portable electronic devices, wearable electronic devices, e-book readers, etc. For example, the display device can be suitably used in xR devices such as VR devices and AR devices.

[0437] FIG. 17A is a diagram showing the appearance of the camera 8000 with the viewfinder 8100 attached.

[0438] The camera 8000 includes a housing 8001, a display unit 8002, operation buttons 8003, a shutter button 8004, and the like. A detachable lens 8006 is attached to the camera 8000. Note that the lens 8006 and the housing of the camera 8000 may be integrated together.

[0439] The camera 8000 can capture an image by pressing a shutter button 8004 or touching a display portion 8002 that functions as a touch panel.

[0440] The housing 8001 has a mount with electrodes, and can be connected to a finder 8100 as well as a strobe device and the like.

[0441] The finder 8100 includes a housing 8101, a display portion 8102, a button 8103, and the like.

[0442] The housing 8101 is attached to the camera 8000 by a mount that engages with the mount of the camera 8000. The viewfinder 8100 can display an image received from the camera 8000 on a display portion 8102.

[0443] The button 8103 has a function as a power button or the like.

[0444] A display device according to one embodiment of the present invention can be applied to a display portion 8002 of a camera 8000 and a display portion 8102 of a finder 8100. Note that the finder 8100 may be built in the camera 8000.

[0445] FIG. 17B is a diagram showing the appearance of the head-mounted display 8200.

[0446] The head-mounted display 8200 includes a mounting portion 8201, a lens 8202, a main body 8203, a display portion 8204, and a cable 8205. The mounting portion 8201 has a built-in battery 8206.

[0447] A cable 8205 supplies power from a battery 8206 to the main body 8203. The main body 8203 includes a wireless receiver or the like and can display received video information on a display portion 8204. The main body 8203 also includes a camera and can use information on the movement of the user's eyeballs or eyelids as an input means.

[0448] The wearing unit 8201 may have a function of recognizing the line of sight by providing a plurality of electrodes at positions that come into contact with the user and capable of detecting a current that flows in association with the movement of the user's eyeballs. The wearing unit 8201 may also have a function of monitoring the user's pulse rate based on the current that flows through the electrodes. The wearing unit 8201 may also have various sensors such as a temperature sensor, a pressure sensor, and an acceleration sensor, and may also have a function of displaying biometric information of the user on the display unit 8204 and a function of changing an image displayed on the display unit 8204 in accordance with the movement of the user's head.

[0449] A display device according to one embodiment of the present invention can be applied to the display portion 8204.

[0450] 17C to 17E are diagrams showing the appearance of a head mounted display 8300. The head mounted display 8300 includes a housing 8301, a display portion 8302, a band-shaped fixture 8304, and a pair of lenses 8305.

[0451] A user can view the display on the display portion 8302 through the lens 8305. Note that it is preferable to curve the display portion 8302 because the user can feel a high sense of presence. In addition, by viewing different images displayed in different regions of the display portion 8302 through the lens 8305, three-dimensional display using parallax can be performed. Note that the present invention is not limited to a configuration in which one display portion 8302 is provided, and two display portions 8302 may be provided, with one display portion provided for each eye of the user.

[0452] A display device according to one embodiment of the present invention can be applied to the display portion 8302. The display device according to one embodiment of the present invention can also achieve extremely high definition. For example, even when the display is enlarged and viewed using the lens 8305 as shown in FIG. 17E , the pixels are difficult for a user to view. That is, the display portion 8302 can be used to allow a user to view a highly realistic image.

[0453] 17F is a diagram showing the appearance of a goggle-type head-mounted display 8400. The head-mounted display 8400 includes a pair of housings 8401, an attachment portion 8402, and a buffer member 8403. A display portion 8404 and a lens 8405 are provided in each of the pair of housings 8401. By displaying different images on the pair of display portions 8404, three-dimensional display using parallax can be performed.

[0454] A user can view the display portion 8404 through the lens 8405. The lens 8405 has a diopter adjustment mechanism, and the position of the lens 8405 can be adjusted according to the user's eyesight. The display portion 8404 is preferably a square or a horizontally long rectangle. This can enhance the sense of realism.

[0455] The wearing section 8402 is preferably adjustable to fit the size of the user's face and has plasticity and elasticity to prevent it from slipping off. Furthermore, a portion of the wearing section 8402 preferably has a vibration mechanism that functions as a bone conduction earphone. This allows the user to enjoy video and audio simply by wearing the earphone, without the need for separate audio equipment such as earphones or speakers. The housing 8401 may also have a function for outputting audio data via wireless communication.

[0456] The mounting portion 8402 and the buffer member 8403 are portions that come into contact with the user's face (forehead, cheeks, etc.). The close contact of the buffer member 8403 with the user's face can prevent light leakage and enhance the sense of immersion. The buffer member 8403 is preferably made of a soft material so that it can be in close contact with the user's face when the user wears the head-mounted display 8400. For example, materials such as rubber, silicone rubber, urethane, and sponge can be used. Furthermore, using a sponge or the like with its surface covered with cloth, leather (natural leather or synthetic leather), or the like can prevent gaps from forming between the user's face and the buffer member 8403, thereby effectively preventing light leakage. Furthermore, using such a material is preferable because it feels pleasant to the touch and prevents the user from feeling cold when worn in cold seasons. It is preferable that the buffer member 8403 or the mounting portion 8402, or other components that come into contact with the user's skin, are removable for easy cleaning or replacement.

[0457] This embodiment mode can be implemented by appropriately combining at least a part thereof with other embodiment modes described in this specification.

[0458] PIX: pixel circuit, RES: resistive element, SW: switch, 10: display device, 20: layer, 21a: circuit, 21b: circuit, 21: source driver, 22: gate driver, 23: functional circuit, 25: region, 30a: layer, 30b: layer, 30: layer, 31: divided pixel array, 34: latch circuit, 35: pass transistor logic circuit, 51: receiver circuit, 52: serial-to-parallel converter circuit, 53: shift register circuit, 54: latch circuit, 55: level shift circuit, 56: voltage generation circuit, 57: bandgap reference circuit, 58: bias generation circuit, 5 9: buffer amplifier circuit, 100: transistor, 102: substrate, 104e: conductive layer, 104: conductive layer, 106: insulating layer, 108: semiconductor layer, 110a: insulating layer, 110b: insulating layer, 110c: insulating layer, 110: insulating layer, 112a: conductive layer, 112a_1: conductive layer, 112a_2: conductive layer, 112b: conductive layer, 141: opening, 150: insulating layer, 151: opening, 200A: display panel, 200a: display panel, 200b: display panel, 200: display panel, 201: layer, 210a: light-emitting element, 210B: light-emitting element, 210b: light-emitting element, 210c: light-emitting element , 210G: light-emitting element, 210R: light-emitting element, 210: light-emitting element, 211B: pixel electrode, 211C: connection electrode, 211G: pixel electrode, 211R: pixel electrode, 211: pixel electrode, 212b: conductive layer, 212B: organic layer, 212G: organic layer, 212R: organic layer, 212W: organic layer, 212: organic layer, 213: common electrode, 214: common layer, 215B: conductive layer, 215G: conductive layer, 215R: conductive layer, 216B: colored layer, 216G: colored layer, 216R: colored layer, 221: protective layer, 222: insulating layer, 223: insulating layer, 224a: pixel, 224b: pixel, 225: insulating layer, 226: resin layer, 228: layer, 230: connection portion, 240: capacitance, 241: conductive layer, 243: insulating layer, 245: conductive layer, 250: pixel, 251: conductive layer, 252: conductive layer, 253: conductive layer, 254: insulating layer, 255a: insulating layer, 255b: insulating layer, 255c: insulating layer, 256: plug, 257: through electrode, 258: conductive layer, 259: conductive layer, 261: insulating layer, 262: insulating layer, 264: insulating layer, 265: insulating layer, 266: insulating layer, 267: insulating layer, 268: insulating layer, 270: substrate, 271: plug, 272: plug, 273: plug, 274: plug,275: plug, 276: adhesive layer, 280: display module, 281: display section, 282: circuit section, 283: circuit section, 284a: pixel, 284: circuit section, 285: terminal section, 286: wiring section, 290: FPC, 291: substrate, 292: substrate, 301: substrate, 310: transistor, 311: conductive layer, 312: low resistance region, 313: insulating layer, 314: insulating layer, 315: element isolation layer, 320A: transistor, 320B: transistor, 321: semiconductor layer, 323: Insulating layer, 324: conductive layer, 325: conductive layer, 326: insulating layer, 327: conductive layer, 328: insulating layer, 329: insulating layer, 332: insulating layer, 333: insulating layer, 334: insulating layer, 335: insulating layer, 336: insulating layer, 761: lower electrode, 762: upper electrode, 763a: light-emitting unit, 763b: light-emitting unit, 763c: light-emitting unit, 763: EL layer, 764: layer, 771a: light-emitting layer, 771b: light-emitting layer, 771c: light-emitting layer, 771: light-emitting layer, 772a: light-emitting layer, 72b: light-emitting layer, 772c: light-emitting layer, 772: light-emitting layer, 773: light-emitting layer, 780a: layer, 780b: layer, 780c: layer, 780: layer, 781: layer, 782: layer, 785: charge-generating layer, 790a: layer, 790b: layer, 790c: layer, 790: layer, 791: layer, 792: layer, 8000: camera, 8001: housing, 8002: display unit, 8003: operation button, 8004: shutter button, 8006: lens, 8100: viewfinder, 8101: housing, 8102 : Display unit, 8103: Button, 8200: Head mounted display, 8201: Mounting unit, 8202: Lens, 8203: Main body, 8204: Display unit, 8205: Cable, 8206: Battery, 8300: Head mounted display, 8301: Housing, 8302: Display unit, 8304: Fixing device, 8305: Lens, 8400: Head mounted display, 8401: Housing, 8402: Mounting unit, 8403: Cushioning member, 8404: Display unit, 8405: Lens,

Claims

1. a pixel circuit; and a drive circuit having an area overlapping the pixel circuit; the drive circuit includes a first circuit and a second circuit; the second circuit has an area overlapping with the first circuit; the pixel circuit has an area overlapping with the second circuit, the first circuit includes a first transistor having silicon in a channel forming region; the second circuit includes a second transistor having a metal oxide in a channel formation region; the pixel circuit includes a third transistor having a metal oxide in a channel formation region, a first conductive layer, a second conductive layer, a first insulating layer, a third conductive layer, a semiconductor layer, a second insulating layer, and a fourth conductive layer on a substrate; the second conductive layer has a region in contact with an upper surface of the first conductive layer and has a first opening; the first insulating layer has a region in contact with an upper surface of the second conductive layer and a region in contact with an upper surface of the first conductive layer, and has a second opening; the third conductive layer has a region in contact with an upper surface of the first insulating layer and has a third opening; the first opening, the second opening, and the third opening overlap each other; the semiconductor layer has a region in contact with the first conductive layer inside the first opening, a region along a sidewall of the second opening, and a region along a sidewall of the third opening; the second insulating layer has a region in contact with an upper surface of the semiconductor layer, the fourth conductive layer has a region in contact with an upper surface of the second insulating layer, an upper surface of the semiconductor layer has a first recess that reflects the second opening and the third opening; an upper surface of the second insulating layer has a second recess that reflects the first recess; the fourth conductive layer has a region embedded in the second recess, the first conductive layer and the second conductive layer function as one of a source electrode and a drain electrode of the second transistor; the third conductive layer functions as the other of the source electrode and the drain electrode of the second transistor, the semiconductor layer has a channel formation region of the second transistor, the fourth conductive layer functions as a gate electrode of the second transistor, the first conductive layer and the third conductive layer include one or more of an oxide conductor and a nitride conductor; the second conductive layer comprises one or more of copper, aluminum, titanium, tungsten, and molybdenum; The display device, wherein the second conductive layer does not have a region in contact with the semiconductor layer.

2. In claim 1, The display device, wherein the metal oxide is indium oxide.