# US 8,772,784 B2 · Semiconductor device including pair of electrodes and oxide semiconductor film with films of low conductivity therebetween

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- Number: US 8,772,784 B2
- Document ID: US8772784B2
- Status: Granted
- Kind: B2
- Application number: 13/772,692
- Filed: 2013-02-21
- Published: 2013-07-11
- Granted: 2014-07-08
- Earliest claimed: 2008-12-25
- Assignees: Semiconductor Energy Laboratory Co., Ltd.
- Applicants: Semiconductor Energy Laboratory Co., Ltd.
- Inventors: Kengo Akimoto; Masashi Tsubuku
- Web page: https://patentgrep.com/patent/US8772784B2

## CPC

- H10H 20/062: {Light-emitting semiconductor devices having field effect type light-emitting regions, e.g. light-emitting High-Electron Mobility Transistors}
- H10D 30/6704: {having supplementary regions or layers in the thin films or in the insulated bulk substrates for controlling properties of the device}
- H10D 30/6713: {characterised by the properties of the source or drain regions, e.g. compositions or sectional shapes}
- H10D 30/6755: {Oxide semiconductors, e.g. zinc oxide, copper aluminium oxide or cadmium stannate}
- H10D 99/00: Subject matter not provided for in other groups of this subclass
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

One of factors that increase the contact resistance at the interface between a first semiconductor layer where a channel is formed and source and drain electrode layers is a film with high electric resistance formed by dust or impurity contamination of a surface of a metal material serving as the source and drain electrode layers. As a solution, a first protective layer and a second protective layer including a second semiconductor having a conductivity that is less than or equal to that of the first semiconductor layer is stacked successively over source and drain electrode layers without exposed to air, the stack of films is used for the source and drain electrode layers.

## Claims

### Claim 1

A semiconductor device comprising:
a first electrode;
a second electrode;
a first semiconductor film over the first electrode;
a second semiconductor film over the second electrode;
an oxide semiconductor film over the first semiconductor film and the second semiconductor film;
an insulating film over the oxide semiconductor film; and
a gate electrode over the insulating film,
wherein the oxide semiconductor film comprises indium and zinc,
wherein the first semiconductor film and the second semiconductor film each have a conductivity less than the oxide semiconductor film,
wherein the first semiconductor film and the second semiconductor film each have smaller thickness than the oxide semiconductor film, and
wherein the oxide semiconductor film comprises sodium at a concentration of 5×1018/cm3 or lower.

### Claim 2 (depends on 1)

The semiconductor device according to claim 1, wherein the oxide semiconductor film further comprises gallium.

### Claim 3 (depends on 1)

The semiconductor device according to claim 1,
wherein the first semiconductor film is a first protective film, and
wherein the second semiconductor film is a second protective film.

### Claim 4 (depends on 1)

The semiconductor device according to claim 1, wherein the oxide semiconductor film is in contact with a side surface of the first electrode and a side surface of the second electrode.

### Claim 5 (depends on 1)

The semiconductor device according to claim 1, wherein the oxide semiconductor film is in contact with a side surface of the first semiconductor film and a side surface of the second semiconductor film.

### Claim 6 (depends on 1)

The semiconductor device according to claim 1, wherein the first semiconductor film and the second semiconductor film each comprise oxide semiconductor.

### Claim 7 (depends on 1)

The semiconductor device according to claim 1, wherein the first electrode and the second electrode are over a substrate.

### Claim 8

A display device comprising:
a first electrode;
a second electrode;
a first semiconductor film over the first electrode;
a second semiconductor film over the second electrode;
an oxide semiconductor film over the first semiconductor film and the second semiconductor film;
a first insulating film over the oxide semiconductor film;
a gate electrode over the first insulating film;
a second insulating film over the gate electrode; and
a pixel electrode over the second insulating film and electrically connected to the first electrode or the second electrode,
wherein the oxide semiconductor film comprises indium and zinc,
wherein the first semiconductor film and the second semiconductor film each have a conductivity less than the oxide semiconductor film,
wherein the first semiconductor film and the second semiconductor film each have smaller thickness than the oxide semiconductor film, and
wherein the oxide semiconductor film comprises sodium at a concentration of 5×1018/cm3 or lower.

### Claim 9 (depends on 8)

The display device according to claim 8, wherein the oxide semiconductor film further comprises gallium.

### Claim 10 (depends on 8)

The display device according to claim 8,
wherein the first semiconductor film is a first protective film, and
wherein the second semiconductor film is a second protective film.

### Claim 11 (depends on 8)

The display device according to claim 8, wherein the oxide semiconductor film is in contact with a side surface of the first electrode and a side surface of the second electrode.

### Claim 12 (depends on 8)

The display device according to claim 8, wherein the oxide semiconductor film is in contact with a side surface of the first semiconductor film and a side surface of the second semiconductor film.

### Claim 13 (depends on 8)

The display device according to claim 8, wherein the first semiconductor film and the second semiconductor film each comprise oxide semiconductor.

### Claim 14 (depends on 8)

The display device according to claim 8, wherein the first electrode and the second electrode are over a substrate.

### Claim 15 (depends on 8)

The display device according to claim 8, further comprising a liquid crystal layer over the pixel electrode.

### Claim 16 (depends on 8)

The display device according to claim 8, further comprising:
a light-emitting layer over the pixel electrode; and
a third electrode over the light-emitting layer.

### Claim 17 (depends on 1)

The semiconductor device according to claim 1, wherein each of the first semiconductor film and the second semiconductor film comprises indium and zinc.

### Claim 18 (depends on 9)

The display device according to claim 9, wherein each of the first semiconductor film and the second semiconductor film comprises indium and zinc.