# US 12,120,915 B2 · Display device with driving transistor having upper and lower gate electrodes

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 12,120,915 B2
- Document ID: US12120915B2
- Status: Granted
- Kind: B2
- Application number: 17/275,508
- Filed: 2018-09-18
- Published: 2022-04-14
- Granted: 2024-10-15
- Earliest claimed: 2018-09-18
- Assignees: Sharp Kabushiki Kaisha
- Applicants: Sharp Kabushiki Kaisha
- Inventors: Tadayoshi Miyamoto; Yoshinobu Nakamura; Kayo Haruguchi
- Web page: https://patentgrep.com/patent/US12120915B2

## CPC

- G09G 3/3233: with pixel circuitry controlling the current through the light-emitting element
- H10K 59/1213: {the pixel elements being TFTs}
- G09F 9/30: in which the desired character or characters are formed by combining individual elements (panels comprising a number of electrodes in a single cell controlling light arriving from an independent light source, e.g. electro-optical or magneto-optical cell, G02F1/00)
- G09G 3/20: for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix {no fixed position being assigned to or needed to be assigned to the individual characters or partial characters}
- H10D 86/471: {having different architectures, e.g. having both top-gate and bottom-gate TFTs}
- H10K 59/1216: {the pixel elements being capacitors}
- H10D 30/6734: {having gate electrodes arranged on both top and bottom sides of the channel, e.g. dual-gate TFTs}
- H10D 30/6755: {Oxide semiconductors, e.g. zinc oxide, copper aluminium oxide or cadmium stannate}
- H10D 86/423: {comprising semiconductor materials not belonging to the Group IV, e.g. InGaZnO}
- H10D 86/481: {integrated with passive devices, e.g. auxiliary capacitors}
- H10D 86/60: wherein the TFTs are in active matrices
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES
- G09F: DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A display device includes a drive transistor and a switching transistor formed by layering an inorganic insulating film, an oxide semiconductor layer, an upper gate insulating layer, an upper gate electrode, and an interlayer insulating film. The drive transistor and the switching transistor include an oxide semiconductor film formed of the oxide semiconductor layer and provided in an island shape corresponding to the drive transistor and an island shape corresponding to the switching transistor, and the oxide semiconductor film includes a channel region overlapping with the upper gate electrode corresponding to the oxide semiconductor film, and a source region and a drain region. The drive transistor is provided with a lower gate electrode and a lower gate insulating layer between the inorganic insulating film and the oxide semiconductor layer. The length of lower gate electrode is less than or equal to the length of upper gate electrode.

## Claims

### Claim 1

A display device comprising, on a substrate,
a pixel circuit including a drive transistor and a switching transistor formed by layering an inorganic insulating film, an oxide semiconductor layer, an upper gate insulating layer, an upper gate electrode, and an interlayer insulating film,
wherein the drive transistor and the switching transistor include an oxide semiconductor film formed of the oxide semiconductor layer and provided in an island shape corresponding to the drive transistor and an island shape corresponding to the switching transistor,
the oxide semiconductor film includes a channel region overlapping with the upper gate electrode corresponding to the oxide semiconductor film, and a source region and a drain region provided sandwiching the channel region between the source region and the drain region,
in the drive transistor and the switching transistor, the upper gate electrode, the upper gate insulating layer, and the channel region corresponding to each of the drive transistor and the switching transistor are aligned in a plan view,
the drive transistor is provided with a lower gate electrode and a lower gate insulating layer between the inorganic insulating film and the oxide semiconductor layer,
in the drive transistor, a film thickness of the lower gate insulating layer between an uppermost surface of the lower gate electrode and the oxide semiconductor film is greater than a film thickness of the upper gate insulating layer,
the upper gate electrode includes a plurality of conductive films, and
in a channel length direction in which the source region and the drain region are opposite each other, a length of the lower gate electrode of the drive transistor is less than or equal to a length of each of the plurality of conductive films.

### Claim 2 (depends on 1)

The display device according to claim 1,
wherein in the drive transistor, a gate signal is applied to the lower gate electrode and a fixed voltage is applied to the upper gate electrode.

### Claim 3 (depends on 2)

The display device according to claim 2,
wherein the fixed voltage is a ground potential.

### Claim 4 (depends on 1)

The display device according to claim 1,
wherein in the switching transistor, a gate signal is applied to the upper gate electrode.

### Claim 5 (depends on 1)

The display device according to claim 1, further comprising:
a terminal electrode layered on the interlayer insulating film,
wherein the terminal electrode is electrically connected to the source region and the drain region corresponding to the terminal electrode via a contact hole formed in the interlayer insulating film.

### Claim 6 (depends on 1)

The display device according to claim 1,
wherein the pixel circuit includes the switching transistor to serve as a writing control transistor.

### Claim 7 (depends on 6)

The display device according to claim 6,
wherein in the writing control transistor, a gate signal is applied to the upper gate electrode.

### Claim 8 (depends on 7)

The display device according to claim 7,
wherein the writing control transistor is not provided with the lower gate electrode.

### Claim 9 (depends on 6)

The display device according to claim 6,
wherein the pixel circuit further includes a capacitor including a first electrode and a second electrode, and
the capacitor includes the first electrode electrically connected to the lower gate electrode of the drive transistor and the second electrode electrically connected to the source region of the drive transistor.

### Claim 10 (depends on 9)

The display device according to claim 9, further comprising:
a plurality of light-emitting elements formed on the interlayer insulating film,
wherein each of the plurality of light-emitting elements is formed by layering an anode electrode, a light-emitting layer, and a cathode electrode in this order on the interlayer insulating film, and
the cathode electrode is configured to be shared by the plurality of light-emitting elements.

### Claim 11 (depends on 10)

The display device according to claim 10,
wherein the pixel circuit includes the switching transistor to serve as a light emission control transistor, and
the drive transistor is provided between each of the plurality of light-emitting elements and the light emission control transistor.

### Claim 12 (depends on 9)

The display device according to claim 9, further comprising:
a plurality of light-emitting elements formed on the interlayer insulating film,
wherein each of the plurality of light-emitting elements is formed by layering an anode electrode, a light-emitting layer, and a cathode electrode in this order on the interlayer insulating film, and
the anode electrode is configured to be shared by the plurality of light-emitting elements.

### Claim 13 (depends on 12)

The display device according to claim 12,
wherein the pixel circuit includes the switching transistor to serve as a light emission control transistor, and
the light emission control transistor is provided between the drive transistor and a high power supply voltage wiring line.

### Claim 14 (depends on 1)

The display device according to claim 1,
wherein the oxide semiconductor film is formed of a material including an In—Ga—Zn—O based semiconductor.

### Claim 15 (depends on 14)

The display device according to claim 14,
wherein the In—Ga—Zn—O based semiconductor includes a crystalline portion.