# US 8,772,778 B2 · Semiconductor device and manufacturing method thereof

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- Number: US 8,772,778 B2
- Document ID: US8772778B2
- Status: Granted
- Kind: B2
- Application number: 13/396,717
- Filed: 2012-02-15
- Published: 2012-08-16
- Granted: 2014-07-08
- Earliest claimed: 2000-03-06
- Assignees: Semiconductor Energy Laboratory Co., Ltd.
- Applicants: Shunpei Yamazaki; Jun Koyama; Hideomi Suzawa; Koji Ono; Tatsuya Arao
- Inventors: Shunpei Yamazaki; Jun Koyama; Hideomi Suzawa; Koji Ono; Tatsuya Arao
- Web page: https://patentgrep.com/patent/US8772778B2

## CPC

- H10D 86/60: wherein the TFTs are in active matrices
- H10D 30/6715: {characterised by the doping profiles, e.g. having lightly-doped source or drain extensions}
- H10D 30/673: {characterised by the shapes, relative sizes or dispositions of the gate electrodes}
- H10D 30/6739: {Conductor-insulator-semiconductor electrodes}
- H10D 86/0221: {comprising manufacture, treatment or patterning of TFT semiconductor bodies}
- H10D 86/421: {having a particular composition, shape or crystalline structure of the active layer}
- H10D 86/441: {Interconnections, e.g. scanning lines}
- H10D 86/481: {integrated with passive devices, e.g. auxiliary capacitors}
- G02F 1/13454: {Drivers integrated on the active matrix substrate (G02F1/136277 takes precedence)}
- H10D 30/6721: {having lightly-doped extensions consisting of multiple lightly doped zones or having non-homogeneous dopant distributions, e.g. graded LDD}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS

## Abstract

A high reliability semiconductor display device is provided. A semiconductor layer in the semiconductor display device has a channel forming region, an LDD region, a source region, and a drain region, and the LDD region overlaps a first gate electrode, sandwiching a gate insulating film.

## Claims

### Claim 1

A semiconductor device comprising:
a semiconductor film over an insulating surface;
a gate insulating film over the semiconductor film; and
a gate electrode comprising:
a first conductive layer over the gate insulating film; and
a second conductive layer over the first conductive layer;
wherein the semiconductor film includes,
a channel forming region,
LDD regions in contact with the channel forming region,
a source region and a drain region in contact with the LDD regions,
wherein an end portion of the first conductive layer extends beyond an end portion of the second conductive layer,
wherein the LDD regions overlap the first conductive layer with the gate insulating film interposed therebetween,
wherein the second conductive layer has a tapered shape in an end portion of the second conductive layer in cross section,
wherein the first conductive layer comprises at least a first element selected from the group consisting of Ta, W, Ti, Mo, Al, and Cu and the second conductive layer comprises at least a second element selected from the group consisting of Ta, W, Ti, Mo, Al, and Cu, and
wherein the first element is different from the second element.

### Claim 2 (depends on 1)

A semiconductor device according to claim 1, wherein the channel forming region overlaps the second conductive layer with the gate insulating film interposed therebetween.

### Claim 3 (depends on 1)

A semiconductor device according to claim 1 further comprising an EL element,
wherein the EL element comprises:
an anode;
a cathode; and
an EL layer being formed between the anode and the cathode, and
wherein the drain region is electrically connected to one of the anode and the cathode.

### Claim 4 (depends on 1)

A semiconductor device according to claim 1, wherein the first conductive layer has a tapered shape in an end portion thereof in cross section.

### Claim 5 (depends on 1)

A semiconductor device according to claim 1,
wherein the LDD regions include a portion having a concentration gradient of impurity in a range of 1×1017 to 1×1018 atoms/cm3, and
wherein the concentration of the impurity increases as a distance from the channel forming region increases.

### Claim 6 (depends on 1)

A semiconductor device according to claim 1, further comprising an insulating layer over the second conductive layer,
wherein the first conductive layer and the second conductive layer are in contact with the insulating layer.

### Claim 7 (depends on 1)

A semiconductor device according to claim 1, wherein the semiconductor device is one selected from the group consisting of an EL display device, a video camera, a digital camera, a head mount display, a sound reproduction device, an image reproduction device, a personal computer and a portable telephone.

### Claim 8

A semiconductor device comprising:
a semiconductor film over an insulating surface;
a gate insulating film over the semiconductor film; and
a gate electrode comprising:
a first conductive layer over the gate insulating film; and
a second conductive layer over the first conductive layer;
wherein the semiconductor film comprises:
a channel forming region,
LDD regions in contact with the channel forming region, and
a source region and a drain region in contact with the LDD regions,
wherein an end portion of the first conductive layer extends beyond an end portion of the second conductive layer,
wherein the LDD regions overlap the first conductive layer with the gate insulating film interposed therebetween,
wherein the first conductive layer has a tapered shape in cross section in an end portion with a first taper angle,
wherein the second conductive layer has a tapered shape in cross section in an end portion with a second taper angle, and
wherein the first taper angle is different from the second taper angle.

### Claim 9 (depends on 8)

A semiconductor device according to claim 8, wherein the channel forming region overlaps the second conductive layer with the gate insulating film interposed therebetween.

### Claim 10 (depends on 8)

A semiconductor device according to claim 8, further comprising an EL element,
wherein the EL element comprises:
an anode;
a cathode; and
an EL layer being formed between the anode and the cathode, and
wherein the drain region is electrically connected to one of the anode and the cathode.

### Claim 11 (depends on 8)

A semiconductor device according to claim 8,
wherein the LDD regions include a portion having a concentration gradient of impurity in a range of 1×1017 to 1×1018 atoms/cm3, and
wherein the concentration of the impurity increases as a distance from the channel forming region increases.

### Claim 12 (depends on 8)

A semiconductor device according to claim 8,
wherein the first conductive layer comprises at least a first element selected from the group consisting of Ta, W, Ti, Mo, Al, and Cu and the second conductive layer comprises at least a second element selected from the group consisting of Ta, W, Ti, Mo, Al, and Cu, and
wherein the first element is different from the second element.

### Claim 13 (depends on 8)

A semiconductor device according to claim 8, wherein the semiconductor device is one selected from the group consisting of an EL display device, a video camera, a digital camera, a head mount display, a sound reproduction device, an image reproduction device, a personal computer and a portable telephone.

### Claim 14

A semiconductor device comprising:
a semiconductor film over an insulating surface;
a gate insulating film over the semiconductor film; and
a gate electrode comprising:
a first conductive layer over the gate insulating film; and
a second conductive layer over the first conductive layer,
wherein the semiconductor film comprises:
a channel forming region,
LDD regions in contact with the channel forming region,
a source region and a drain region in contact with the LDD regions,
wherein the gate insulating film overlaps the source region and the drain region,
wherein an end portion of the first conductive layer extends beyond an end portion of the second conductive layer,
wherein the LDD regions overlap the first conductive layer with the gate insulating film interposed therebetween, and
wherein a part of the gate insulating film overlapped with the first conductive layer is thicker than a part of the gate insulating film overlapped with one of the source region and the drain region of the semiconductor layer and not overlapped with the first conductive layer.

### Claim 15 (depends on 14)

A semiconductor device according to claim 14, wherein the channel forming region overlaps the second conductive layer with the gate insulating film interposed therebetween.

### Claim 16 (depends on 14)

A semiconductor device according to claim 14, further comprising an EL element,
wherein the EL element comprises:
an anode;
a cathode; and
an EL layer being formed between the anode and the cathode, and
wherein the drain region is electrically connected to one of the anode and the cathode.

### Claim 17 (depends on 14)

A semiconductor device according to claim 14, wherein the first conductive layer has a tapered shape in an end portion thereof in cross section.

### Claim 18 (depends on 14)

A semiconductor device according to claim 14,
wherein the LDD regions include a portion having a concentration gradient of impurity in a range of 1×1017 to 1×1018 atoms/cm3, and
wherein the concentration of the impurity increases as a distance from the channel forming region increases.

### Claim 19 (depends on 14)

A semiconductor device according to claim 14,
wherein the first conductive layer comprises at least a first element selected from the group consisting of Ta, W, Ti, Mo, Al, and Cu and the second conductive layer comprises at least a second element selected from the group consisting of Ta, W, Ti, Mo, Al, and Cu, and
wherein the first element is different from the second element.

### Claim 20 (depends on 14)

A semiconductor device according to claim 14, wherein the semiconductor device is one selected from the group consisting of an EL display device, a video camera, a digital camera, a head mount display, a sound reproduction device, an image reproduction device, a personal computer and a portable telephone.