Semiconductor device

• US 6,365,917 B1
• Filed: 11/16/1999
• Issued: 04/02/2002
• Est. Priority Date: 11/25/1998
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Primary Examiner(s): Flynn, Nathan
• Assistant Examiner(s): FORDE, REMMON R
• Application Number:
  US09/440,633
• Time in Patent Office: 868 Days
• Field of Search: 349/42, 349/43, 349/44, 349/46, 357/57, 357/59, 357/66, 357/72, 357/347, 357/350, 357/351
• US Class Current: 257/72
• 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 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• 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

Abstract

In order to realize a higher reliability TFT and a high reliability semiconductor device, an NTFT of the present invention has a channel forming region, n-type first, second, and third impurity regions in a semiconductor layer. The second impurity region is a low concentration impurity region that overlaps a tapered potion of a gate electrode with a gate insulating film interposed therebetween, and the impurity concentration of the second impurity region increases gradually from the channel forming region to the first impurity region. And, the third impurity region is a low concentration impurity region that does not overlap the gate electrode.

Moreover, a plurality of NTFTs on the same substrate should have different second impurity region lengths, respectively, according to difference of the operating voltages. That is, when the operating voltage of the second TFT is higher than the operating voltage of the first TFT, the length of the second impurity region is longer on the second TFT than on the first TFT.

Claims

1. A semiconductor device comprising:

at least a driver portion and a pixel portion over a substrate, said driver portion comprising first and second TFTs, and each of said first and second TFTs comprising;

a semiconductor layer having a channel forming region, a first impurity region, a second impurity region, and a third impurity region formed between said first impurity region and said second impurity region; and

a gate electrode adjacent to said semiconductor layer with a gate insulating film interposed therebetween,

wherein said second impurity region is located in said semiconductor layer so as to overlap said gate electrode with said gate insulating film interposed therebetween,

wherein a concentration of an impurity element included in said second impurity region shows a concentration gradient that increases as a distance from said third impurity region decreases,

wherein a length of the second impurity region formed in said first TFT is smaller than that of the second impurity region formed in said second TFT.

2. A device according to claim 1, wherein an angle formed between a side of said gate electrode and said gate insulating film is from 3°

to 40°

.

3. A device according to claim 1, wherein said first impurity region, said second impurity region, and said third impurity region include a periodic table group 15 element, and

wherein said first impurity region includes the periodic table group 15 element in a concentration which is greater than in said second impurity region and in said third impurity region.

4. A device according to claim 1, wherein said semiconductor device is an EL display device.

5. Electronic equipment, wherein said electronic equipment uses a semiconductor device according to claim 1.

6. An electronic equipment according to claim 5, wherein said electronic equipment is selected from the group consisting of a video camera, a digital camera, a projector, a projection television, a goggle-type display, a head mount display, a navigation system for vehicles, a sound reproduction device, a note-type personal computer, game equipment, a portable information terminal, a mobile computer, a cellular phone, a handheld game unit, an electronic book, and an imaging device equipped with recording medium.

31. A device according to claim 1, wherein said first TFT is included in at least one circuit selected from the group consisting of a shift register circuit and a signal processing circuit, and said second TFT is included in at least one circuit selected from the group consisting of a level shifter circuit, a buffer circuit, a sampling circuit, and a pre-charge circuit.

7. A semiconductor device comprising:

first and second CMOS circuits on a substrate, each of said first and second CMOS circuits including NTFTs comprising;

a semiconductor layer having a channel forming region, a first impurity region, a second impurity region, and a third impurity region formed between said first impurity region and said second impurity region; and

a gate electrode adjacent to said semiconductor layer with a gate insulating film interposed therebetween,

wherein said second impurity region is located in said semiconductor layer so as to overlap said gate electrode with said gate insulating film interposed therebetween,

wherein a concentration of a periodic table group 15 element included in said second impurity region shows a concentration gradient that increases as a distance from said third impurity region decreases, and

wherein a length of the second impurity region formed in said NTFT of said first CMOS is smaller than that of the second impurity region formed in said NTFT of said second CMOS.

8. A device according to claim 7, wherein an angle formed between a side of said gate electrode and said gate insulating film is from 3°

to 40°

.

9. A device according to claim 7, wherein said first impurity region, said second impurity region, and said third impurity region include said periodic table group 15 element, and

wherein said first impurity region includes the periodic table group 15 element in a concentration which is greater than in said second impurity region and in said third impurity region.

10. A device according to claim 7, wherein said semiconductor device is an EL display device.

11. Electronic equipment, wherein said electronic equipment uses a semiconductor device according to claim 10.

12. An electronic equipment according to claim 7, wherein said electronic equipment is selected from the group consisting of a video camera, a digital camera, a projector, a projection television, a goggle-type display, a head mount display, a navigation system for vehicles, a sound reproduction device, a note-type personal computer, game equipment, a portable information terminal, a mobile computer, a cellular phone, a handheld game unit, an electronic book, and an imaging device equipped with recording medium.

32. A device according to claim 7, wherein said first and second CMOS circuits are located in a driver portion of said semiconductor device.

13. A semiconductor device comprising:

first and second NTFTs on a substrate, each of said first and second NTFTs comprising;

a semiconductor layer having a channel forming region, a first impurity region, a second impurity region, and a third impurity region formed between said first impurity region and said second impurity region;

a first gate electrode adjacent to said semiconductor layer with a gate insulating film interposed therebetween,

a second gate electrode on said first gate electrode,

wherein said second impurity region is located in said semiconductor layer so as to overlap at least said first gate electrode with said gate insulating film interposed therebetween,

wherein a concentration of a periodic table group 15 element included in said second impurity region shows a concentration gradient that increases as a distance from said third impurity region decreases,

wherein a length of the second impurity region formed in said first NTFT is smaller than that of the second impurity region formed in said second NTFT, and

wherein an operating voltage of said second NTFT is greater than an operating voltage of said first NTFT.

14. A device according to claim 13, wherein an angle formed between a side of said first gate electrode and said gate insulating film is from 3°

to 40°

.

15. A device according to claim 13, wherein said first impurity region, said second impurity region, and said third impurity region include said periodic table group 15 element, and

wherein said first impurity region includes the periodic table group 15 element in a concentration which is greater than in said second impurity region and in said third impurity region.

16. A device according to claim 13, wherein said semiconductor device is an EL display device.

17. Electronic equipment, wherein said electronic equipment uses a semiconductor device according to claim 13.

18. An electronic equipment according to claim 17, wherein said electronic equipment is selected from the group consisting of a video camera, a digital camera, a projector, a projection television, a goggle-type display, a head mount display, a navigation system for vehicles, a sound reproduction device, a note-type personal computer, game equipment, a portable information terminal, a mobile computer, a cellular phone, a handheld game unit, an electronic book, and an imaging device equipped with recording medium.

33. A device according to claim 13, wherein said first and second NTFTs are located in a driver portion of said semiconductor device.

34. A device according to claim 13, wherein said first NTFT is located in a driver portion of said semiconductor device and said second NTFT is located in a pixel portion of said semiconductor device.

35. A device according to claim 13, wherein said first NTFT is located in a pixel portion of said semiconductor device and said second NTFT is located in a driver portion of said semiconductor device.

19. A semiconductor device comprising:

first and second NTFTs on a substrate, each of said first and second NTFTs comprising;

a semiconductor layer having a channel forming region, a first impurity region, a second impurity region, and a third impurity region formed between said first impurity region and said second impurity region; and

a gate electrode adjacent to said semiconductor layer with gate insulting film interposed therebetween,

wherein said second impurity region is located in said semiconductor layer so as to overlap said gate electrode with said gate insulating film interposed therebetween and a portion of said gate electrode that overlaps said second impurity region has a tapered shape,

wherein a length of the second impurity region formed in said first NTFT is smaller than that of the second impurity region formed in said second NTFT, and

wherein said first NTFT is included in a pixel region, and said second NTFT is included in at least one circuit selected from the group consisting of a level shifter circuit, buffer circuit, a sampling circuit, and a pre-charge circuit.

20. A device according to claim 19, wherein an angle formed between a side of said gate electrode and said gate insulating film is from 3°

to 40°

.

21. A device according to claim 19, wherein said first impurity region, said second impurity region, and said third impurity region include said periodic table group 15 element, and

wherein said first impurity region includes the periodic table group 15 element in a concentration which is greater than in said second impurity region and in said third impurity region.

22. A device according to claim 19, wherein said semiconductor device is an EL display device.

23. Electronic equipment, wherein said electronic equipment uses a semiconductor device according to claim 19.

24. An electronic equipment according to claim 23, wherein said electronic equipment is selected from the group consisting of a video camera, a digital camera, a projector, a projection television, a goggle-type display, a head mount display, a navigation system for vehicles, a sound reproduction device, a note-type personal computer, game equipment, a portable information terminal, a mobile computer, a cellular phone, a handheld game unit, an electronic book, and an imaging device equipped with recording medium.

36. A device according to claim 19, wherein a length of said second impurity region formed in said first NTFT is larger than that of a second impurity region of an NTFT in a circuit selected from the group consisting of a shift register circuit and a signal processing circuit.

25. A semiconductor device comprising:

first and second NTFTs on a substrate, each of said first and second NTFTs comprising;

a semiconductor layer having a channel forming region, a first impurity region, a second impurity region, and a third impurity region formed between said first impurity region and said second impurity region; and

a gate electrode adjacent to said semiconductor layer with a gate insulating film interposed therebetween,

wherein said second impurity region is located in said semiconductor layer so as to overlap said gate electrode with said gate insulating film interposed therebetween and a portion of said gate electrode that overlaps said second impurity region has a tapered shape,

wherein a length of the second impurity region formed in said first NTFT is smaller than that of the second impurity region formed in said second NTFT, and

wherein an operating voltage of said second NTFT is greater than an operating voltage of said first NTFT.

26. A device according to claim 25, wherein an angle formed between a side of said gate electrode and said gate insulating film is from 3°

to 40°

.

27. A device according to claim 25, wherein said first impurity region, said second impurity region, and said third impurity region include said periodic table group 15 element, and

wherein said first impurity region includes the periodic table group 15 element in a concentration which is greater than in said second impurity region and in said third impurity region.

28. A device according to claim 25, wherein said semiconductor device is an EL display device.

29. Electronic equipment, wherein said electronic equipment uses a semiconductor device according to claim 25.

30. An electronic equipment according to claim 29, wherein said electronic equipment is selected from the group consisting of a video camera, a digital camera, a projector, a projection television, a goggle-type display, a head mount display, a navigation system for vehicles, a sound reproduction device, a note-type personal computer, game equipment, a portable information terminal, a mobile computer, a cellular phone, a handheld game unit, an electronic book, and an imaging device equipped with recording medium.