Semiconductor device and method of manufacturing the same

• US 8,653,595 B2
• Filed: 04/11/2011
• Issued: 02/18/2014
• Est. Priority Date: 11/09/1998
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei, Adachi, Hiroki
• Primary Examiner(s): Pham, Long
• Application Number:
  US13/083,777
• Publication Number:
  US 20110241012A1
• Time in Patent Office: 1,044 Days
• Field of Search: 257/347, 257/49, 257/50, 257/51, 257/66, 257/69, 257/369
• US Class Current: 257/347
• 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 27/124 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 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 29/6675 Amorphous silicon or polysilicon transistors
• CPC Class Codes: H01L 29/66757 Lateral single gate single channel transistors with non-inverted structure, i.e. the channel layer is formed before the gate
• CPC Class Codes: H01L 29/78621 with LDD structure or an extension or an offset region or characterised by the doping profile
• CPC Class Codes: H01L 29/78627 with a significant overlap between the lightly doped drain and the gate electrode, e.g. GOLDD

Abstract

The present invention relates to a semiconductor device including a circuit composed of thin film transistors having a novel GOLD (Gate-Overlapped LDD (Lightly Doped Drain)) structure. The thin film transistor comprises a first gate electrode and a second electrode being in contact with the first gate electrode and a gate insulating film. Further, the LDD is formed by using the first gate electrode as a mask, and source and drain regions are formed by using the second gate electrode as the mask. Then, the LDD overlapping with the second gate electrode is formed. This structure provides the thin film transistor with high reliability.

Claims

1. A semiconductor device comprising:

a semiconductor layer including a channel formation region;

a gate insulating film over the semiconductor layer;

a gate electrode over the gate insulating film, the gate electrode including a first conductive layer and a second conductive layer over the first conductive layer,

wherein the second conductive layer extends beyond a first side edge of the first conductive layer, and

wherein the second conductive layer does not extend beyond a second side edge of the first conductive layer.

2. The semiconductor layer according to claim 1 wherein the semiconductor layer comprises polycrystalline silicon.

3. The semiconductor layer according to claim 1 wherein the second side edge of the first conductive layer is located outside of the second conductive layer.

4. The semiconductor device according to claim 1 wherein the first conductive layer includes two conductive layers.

5. The semiconductor device according to claim 1 wherein the second conductive layer comprises a material selected from the group consisting of titanium, tantalum, tungsten and molybdenum.

6. A semiconductor device comprising:

a semiconductor layer including a channel formation region;

a gate insulating film over the semiconductor layer;

a gate electrode over the gate insulating film, the gate electrode including a first conductive layer and a second conductive layer over the first conductive layer,

wherein the second conductive layer extends beyond a first side edge of the first conductive layer, and

wherein a second side edge of the first conductive layer is coplanar with a side edge of the second conductive layer, the second side edge of the first conductive layer being located over the gate insulating film.

7. The semiconductor layer according to claim 6 wherein the semiconductor layer comprises polycrystalline silicon.

8. The semiconductor device according to claim 6 wherein the first conductive layer includes two conductive layers.

9. The semiconductor device according to claim 6 wherein the second conductive layer comprises a material selected from the group consisting of titanium, tantalum, tungsten and molybdenum.

10. A semiconductor device comprising:

a semiconductor layer including a channel formation region;

a gate insulating film over the semiconductor layer;

a gate electrode over the gate insulating film, the gate electrode including a first conductive layer and a second conductive layer over the first conductive layer,

a capacitance including a portion of the semiconductor layer and a third conductive layer over the portion of the semiconductor layer with a portion of the gate insulating film interposed therebetween,

wherein the third conductive layer is in contact with the portion of the gate insulating film, and the third conductive layer is formed by patterning a same layer as the second conductive layer.

11. The semiconductor device according to claim 10 further comprising a pixel electrode in electrical contact with the semiconductor layer.

12. The semiconductor device according to claim 10 wherein the first conductive layer includes two conductive layers.

13. The semiconductor device according to claim 10 wherein the second conductive layer comprises a material selected from the group consisting of titanium, tantalum, tungsten and molybdenum.

14. A projector comprising:

a semiconductor layer including a channel formation region;

a gate insulating film over the semiconductor layer;

a gate electrode over the gate insulating film, the gate electrode including a first conductive layer and a second conductive layer over the first conductive layer,

a capacitance including a portion of the semiconductor layer and a third conductive layer over the portion of the semiconductor layer with a portion of the gate insulating film interposed therebetween,

wherein the third conductive layer is in contact with the portion of the gate insulating film, and the third conductive layer is formed by patterning a same layer as the second conductive layer, and

wherein the second conductive layer extends beyond a side edge of the first conductive layer so that the second conductive layer is in contact with a portion of the gate insulating film.

15. The projector according to claim 14 further comprising a pixel electrode in electrical contact with the semiconductor layer.

16. The projector according to claim 14 wherein the first conductive layer includes two conductive layers.

17. The projector according to claim 14 wherein the second conductive layer comprises a material selected from the group consisting of titanium, tantalum, tungsten and molybdenum.