Semiconductor device and method of manufacturing the same

• US 7,923,779 B2
• Filed: 10/31/2005
• Issued: 04/12/2011
• Est. Priority Date: 11/09/1998
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Adachi, Hiroki, Yamazaki, Shunpei
• Primary Examiner(s): Pham; Long
• Application Number:
  US11/263,182
• Publication Number:
  US 20060081931A1
• Time in Patent Office: 1,989 Days
• Field of Search: 257/66, 257/69, 257/347, 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 element having a top gate type LDD structure located on a substrate, comprising:

a lower gate electrode on a gate insulating film, having a top surface and side surfaces;

an upper gate electrode being in contact with the top surface and side surfaces of the lower gate electrode and with the gate insulating film, at least a side thereof on a source electrode side and a drain electrode side protruding from said lower gate electrode, wherein a portion of the upper gate electrode over the lower gate electrode has a first upper surface and a portion of the upper gate electrode which protrudes from said lower gate electrode has a second upper surface, and the first upper surface is located at a higher level from the gate insulating film than the second upper surface; and

a semiconductor section having a channel area directly below said upper gate electrode and said lower gate electrode,

an LDD area directly below a protruding portion of said upper electrode, and

a source area and a drain area not covered with said upper gate electrode and said lower electrode,

wherein said lower gate electrode comprises a low resistance metal material; and

wherein said upper gate electrode comprises a high-density metal material having a density of at least 8 or a hydrogen adsorptive metal, and has a high masking ability of hydrogen ions injected during injection of impurities.

2. The semiconductor element of claim 1 wherein said lower gate electrode comprises a metal material having an electric specific resistance of up to 5 Ω

·

cm.

5. The semiconductor element of claim 1, wherein a length of the LDD area is from 1.0 μ

m to 6 μ

m, and wherein a length of a portion where the upper gate electrode is not overlapped to the LDD area is from 0.5 μ

m to 3 μ

m.

6. The semiconductor element of claim 1, wherein the lower gate electrode is formed from one or more kinds of elements selected from a group consisting of titanium (Ti), tantalum (Ta), tungsten (W), molybdenum (Mo), aluminum (Al), and copper (Cu) or from a material containing those elements as ingredients.

8. The semiconductor element of claim 1, wherein the upper gate electrode is formed from one or more kinds of elements selected from a group consisting of titanium (Ti), tantalum (Ta), tungsten (W), and molybdenum (Mo), or from an alloy material containing those elements as ingredients.

3. Gate type semiconductor element located on a substrate, having gate electrodes comprising an upper gate electrode and a lower gate electrode located one on top of the other in close contact with each other on a gate insulating film, wherein:

said lower gate electrode has a top surface and side surfaces;

said upper gate electrode is in contact with the top surface and side surfaces of the lower gate electrode and with the gate insulating film, wherein a portion of the upper gate electrode over the lower gate electrode has a first upper surface and a portion of the upper gate electrode protrudes from said lower gate electrode and has a second upper surface, and the first upper surface is located at a higher level from the gate insulating film than the second upper surface;

said lower gate electrode comprises a low-resistance metal material; and

said upper gate electrode comprises a high-density metal material having a density of at least 8 or a hydrogen adsorptive metal, and a high-masking electrode having a high masking ability of hydrogen ions injected during injection of impurities.

4. The semiconductor element of claim 3 wherein said lower gate electrode comprises a metal material having an electric specific resistance of up to 5 Ω

·

cm.

7. The semiconductor element of claim 3, wherein the lower gate electrode is formed from one or more kinds of elements selected from a group consisting of titanium (Ti), tantalum (Ta), tungsten (W), molybdenum (Mo), aluminum (Al), and copper (Cu) or from a material containing those elements as ingredients.

9. The semiconductor element of claim 3, wherein the upper gate electrode is formed from one or more kinds of elements selected from a group consisting of titanium (Ti), tantalum (Ta), tungsten (W), and molybdenum (Mo), or from an alloy material containing those elements as ingredients.

10. A semiconductor element having a top gate type LDD structure located on a substrate, comprising:

a lower gate electrode on a gate insulating film, having a top surface and side surfaces;

an upper gate electrode having a first portion in contact with the top surface and side surfaces of the lower gate electrode and with the gate insulating film, at least a side thereof on a source electrode side and a drain electrode side protruding from said lower gate electrode and a second portion which extends horizontally from the first portion and extends horizontally over the gate insulating film; and

a semiconductor section having a channel area directly below said upper gate electrode and said lower gate electrode,

an LDD area directly below a protruding portion of said upper electrode, and

a source area and a drain area not covered with said upper gate electrode and said lower electrode,

wherein said lower gate electrode comprises a low resistance metal material; and

wherein said upper gate electrode comprises a high-density metal material having a density of at least 8 or a hydrogen adsorptive metal, and has a high masking ability of hydrogen ions injected during injection of impurities.

11. The semiconductor element of claim 10 wherein said lower gate electrode comprises a metal material having an electric specific resistance of up to 5 Ω

·

cm.

12. The semiconductor element of claim 10, wherein a length of the LDD area is from 1.0 μ

m to 6 μ

m, and wherein a length of a portion where the upper gate electrode is not overlapped to the LDD area is from 0.5 μ

m to 3 μ

m.

13. The semiconductor element of claim 10, wherein the lower gate electrode is formed from one or more kinds of elements selected from a group consisting of titanium (Ti), tantalum (Ta), tungsten (W), molybdenum (Mo), aluminum (Al), and copper (Cu) or from a material containing those elements as ingredients.

14. The semiconductor element of claim 10, wherein the upper gate electrode is formed from one or more kinds of elements selected from a group consisting of titanium (Ti), tantalum (Ta), tungsten (W), and molybdenum (Mo), or from an alloy material containing those elements as ingredients.