ELECTRONIC APPLIANCE INCLUDING TRANSISTOR HAVING LDD REGION

• US 20070246777A1
• Filed: 09/01/2006
• Published: 10/25/2007
• Est. Priority Date: 03/06/2000
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Suzawa, Hideomi, Ono, Koji, Yamazaki, Shunpei, Koyama, Jun, Arao, Tatsuya
• Granted Patent: US 8,124,973 B2
• Time in Patent Office: Days
• US Class Current: 257/350
• CPC Class Codes: G02F 1/13454 Drivers integrated on the active matrix substrate G02F1/136277 takes precedence
• CPC Class Codes: H01L 2029/7863 with an LDD consisting of more than one lightly doped zone or having a non-homogeneous dopant distribution, e.g. graded LDD
• CPC Class Codes: H01L 27/1222 with a particular composition, shape or crystalline structure of the active layer
• CPC Class Codes: H01L 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H01L 27/1255 integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H01L 27/127 with a particular formation, treatment or patterning of the active layer specially adapted to the circuit arrangement
• CPC Class Codes: H01L 29/42384 for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/78621 with LDD structure or an extension or an offset region or characterised by the doping profile

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

1. A semiconductor device comprising:

a semiconductor film being formed 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 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.

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

3. 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.

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

5. A semiconductor device according to claim 1,

wherein the LDD regions includes 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.

6. 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.

7. 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.

8. A semiconductor device comprising:

a semiconductor film being formed 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.

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

10. 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.

11. A semiconductor device according to claim 8,

wherein the LDD regions includes 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.

12. 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.

13. 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.

14. A semiconductor device comprising:

a semiconductor film being formed 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.

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

16. 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.

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

18. A semiconductor device according to claim 14,

wherein the LDD regions includes 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.

19. 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.

20. 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.