# US 10,483,406 B2 · Semiconductor device including an oxide semiconductor

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- Number: US 10,483,406 B2
- Document ID: US10483406B2
- Status: Granted
- Kind: B2
- Application number: 15/834,590
- Filed: 2017-12-07
- Published: 2018-04-19
- Granted: 2019-11-19
- Earliest claimed: 2012-06-15
- Assignees: Semiconductor Energy Laboratory Co., Ltd.
- Applicants: Semiconductor Energy Laboratory Co., Ltd.
- Inventors: Shunpei Yamazaki
- Web page: https://patentgrep.com/patent/US10483406B2

## CPC

- H10D 30/6757: {characterised by the structure of the channel, e.g. transverse or longitudinal shape or doping profile (TFTs having channel structures for preventing kink or snapback effects H10D30/6708; TFTs having lightly-doped source or drain extensions H10D30/6715)}
- G06F 3/0412: {Digitisers structurally integrated in a display}
- H10D 30/6739: {Conductor-insulator-semiconductor electrodes}
- H10D 30/6756: {Amorphous oxide semiconductors}
- H10D 62/82: Heterojunctions
- H10D 64/683: {being parallel to the channel plane}
- H10D 64/693: {the insulator comprising nitrogen, e.g. nitrides, oxynitrides or nitrogen-doped materials}
- H10F 30/221: the potential barrier being a PN homojunction
- H10F 39/8037: {the integrated elements comprising a transistor}
- H10F 39/80377: {characterised by the channel of the transistor, e.g. channel having a doping gradient}
- H10F 77/1662: {including only Group IV materials}
- G06F 3/04886: by partitioning the display area of the touch-screen or the surface of the digitising tablet into independently controllable areas, e.g. virtual keyboards or menus
- H10K 59/40: OLEDs integrated with touch screens
- H10K 59/65: OLEDs integrated with inorganic image sensors
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES

## Abstract

High field-effect mobility is provided for a transistor including an oxide semiconductor. Further, a highly reliable semiconductor device including the transistor is provided. In a bottom-gate transistor including an oxide semiconductor layer, an oxide semiconductor layer functioning as a current path (channel) of the transistor is sandwiched between oxide semiconductor layers having lower carrier densities than the oxide semiconductor layer. In such a structure, the channel is formed away from the interface of the oxide semiconductor stacked layer with an insulating layer in contact with the oxide semiconductor stacked layer, i.e., a buried channel is formed.

## Claims

### Claim 1

A semiconductor device comprising:
a transistor; and
a photodiode electrically connected to the transistor;
wherein the transistor comprises:
a first oxide semiconductor layer;
a second oxide semiconductor layer over and in direct contact with the first oxide semiconductor layer;
a third oxide semiconductor layer in direct contact with a top surface of the second oxide semiconductor layer;
a gate electrode layer overlapping with the second oxide semiconductor layer with an insulating layer interposed therebetween; and
a source electrode layer and a drain electrode layer electrically connected to the second oxide semiconductor layer,
wherein a difference between a Fermi level and a bottom of a conduction band in the second oxide semiconductor layer is smaller than those in the first oxide semiconductor layer and the third oxide semiconductor layer.

### Claim 2 (depends on 1)

The semiconductor device according to claim 1, wherein the photodiode is over the transistor.

### Claim 3 (depends on 1)

The semiconductor device according to claim 1, wherein the photodiode is electrically connected to the gate electrode layer of the transistor.

### Claim 4 (depends on 1)

The semiconductor device according to claim 1,
wherein the insulating layer is over the gate electrode layer, and
wherein the first oxide semiconductor layer is over the insulating layer.

### Claim 5 (depends on 1)

The semiconductor device according to claim 1, wherein the second oxide semiconductor layer comprises an impurity imparting an n-type conductivity.

### Claim 6 (depends on 1)

The semiconductor device according to claim 1, wherein the third oxide semiconductor layer is in direct contact with a side surface of the second oxide semiconductor layer.

### Claim 7

A semiconductor device comprising:
a transistor; and
a photodiode electrically connected to the transistor;
wherein the transistor comprises:
a first oxide semiconductor layer;
a second oxide semiconductor layer on and in direct contact with the first oxide semiconductor layer;
a third oxide semiconductor layer in direct contact with a top surface of the second oxide semiconductor layer;
a gate electrode layer overlapping with the second oxide semiconductor layer with an insulating layer interposed therebetween; and
a source electrode layer and a drain electrode layer electrically connected to the second oxide semiconductor layer,
wherein a difference between a Fermi level and a bottom of a conduction band in the second oxide semiconductor layer is smaller than those in the first oxide semiconductor layer and the third oxide semiconductor layer, and
wherein the photodiode comprises an amorphous silicon film.

### Claim 8 (depends on 7)

The semiconductor device according to claim 7, wherein the photodiode is over the transistor.

### Claim 9 (depends on 7)

The semiconductor device according to claim 7, wherein the photodiode is electrically connected to the gate electrode layer of the transistor.

### Claim 10 (depends on 7)

The semiconductor device according to claim 7,
wherein the insulating layer is over the gate electrode layer, and
wherein the first oxide semiconductor layer is over the insulating layer.

### Claim 11 (depends on 7)

The semiconductor device according to claim 7, wherein the second oxide semiconductor layer comprises an impurity imparting an n-type conductivity.

### Claim 12 (depends on 7)

The semiconductor device according to claim 7, wherein the third oxide semiconductor layer is in direct contact with a side surface of the second oxide semiconductor layer.