Field effect semiconductor device with immunity to hot carrier effects

• US 5,272,361 A
• Filed: 11/01/1991
• Issued: 12/21/1993
• Est. Priority Date: 06/30/1989
• 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): Hille, Rolf
• Assistant Examiner(s): LOKE, STEVEN HO YIN
• Application Number:
  US07/785,201
• Time in Patent Office: 781 Days
• Field of Search: 357/23.1, 357/23.7, 357/23.15, 257/66, 257/347, 257/348, 257/410, 257/411, 257/77, 257/192
• US Class Current: 257/66
• CPC Class Codes: H01L 29/1054 with a variation of the composition, e.g. channel with strained layer for increasing the mobility

Abstract

An improved field effect semiconductor device comprises source, drain and channel semiconductor regions and a gate electrode formed on the channel region through a gate insulating film. An intervening film is interposed between the channel region and the gate insulating film in order not to form a channel just below the gate insulating film. The intervening film is made, for example, from an amorphous silicon semiconductor whose energy gap is wider than that of the channel region made of polysilicon. By this structure, immunity to hot carrier effects can be given to the device.

Claims

1. A field effect semiconductor device comprising:

an insulating substrate;

a crystalline semiconductor film formed on the substrate;

an intervening film formed on said semiconductor film having an energy gap wider than that of the semiconductor film so that a channel region is formed within the semiconductor film;

source and drain regions respectively formed within source and drain films were the source and drain films are formed on said semiconductor film and where the energy gaps of said source and drain films are wider than that of the semiconductor film;

a gate insulating film formed on said intervening film located between said source and drain regions; and

a gate electrode formed on said gate insulating film.

2. A field effect semiconductor device as in claim 1 wherein said source and drain films and said intervening film are portions of one film formed on the semiconductor film where the energy gap of the one film is wider than that of the semiconductor film.

3. A field effect semiconductor device as in claim 1 wherein said intervening film comprises a material selected from the group consisting of amorphous silicon, silicon nitride, silicon carbide, and silicon oxide.

4. A field effect semiconductor device as in claim 1 where the thickness of said intervening film is 10-1000 angstroms.

5. A field effect semiconductor device comprising:

an insulating substrate;

a crystalline semiconductor film formed on the substrate;

an intervening film formed on said semiconductor film having an energy gap wider than that of the semiconductor film so that a channel region is formed within the semiconductor film;

a source region formed within a source film and said semiconductor film where the source film is formed on said semiconductor film and where the energy gap of said source film is wider than that of said semiconductor film;

a drain region formed within a drain film and said semiconductor film where the drain film is formed on said semiconductor film and where the energy gap of said drain film is wider than that of said semiconductor film and where the junction between the channel region and the drain region is at least within the semiconductor film;

a gate insulating film formed on said intervening film located between said source and drain regions; and

a gate electrode formed on said gate insulating film.

6. A field effect semiconductor device as in claim 5 wherein said source and drain films and said intervening film are portions of one film formed on the semiconductor film where the energy gap of the one film is wider than that of the semiconductor film.

7. A field effect semiconductor device as in claim 5 wherein said intervening film comprises a material selected from the group consisting of amorphous silicon, silicon nitride, silicon carbide, and silicon oxide.

8. A field effect semiconductor device as in claim 5 where the thickness of said intervening film is 10-10000 angstroms.

9. A field effect semiconductor device comprising:

a crystalline silicon semiconductor substrate;

a channel region formed within the substrate;

an intervening film formed on the channel region of said semiconductor substrate where the intervening film has an energy gap wider than the semiconductor substrate;

source and drain regions where the junction between the channel region and the drain region is within the semiconductor substrate;

a gate insulating film formed on said intervening film located between said source and drain regions where the gate insulating film has an energy band gap wider than the intervening film; and

a gate electrode formed on said gate insulating film.

10. A field effect semiconductor device as in claim 9 wherein said intervening film comprises a material selected from the group consisting of amorphous silicon, silicon nitride, silicon carbide, and silicon oxide.

11. The device of claim 10 wherein said silicon nitride is expressed by Si₃ N_1-3.

12. The device of claim 10 wherein said silicon carbide is expressed by SiC₀.2-0.7.

13. The device of claim 10 wherein said silicon oxide is expressed by SiO₀.5-1.5.

14. A field effect semiconductor device as in claim 9 where the thickness of said intervening film is 10-1000 angstroms.

15. A field effect semiconductor device comprising:

a crystalline silicon semiconductor;

an intervening film formed on said semiconductor having an energy gap wider than the semiconductor so that a channel region is formed within the semiconductor where a step transition occurs in the energy gap at the interface between the intervening film and the semiconductor;

source and drain regions;

a gate insulating film formed on said intervening film located between said source and drain regions where the gate insulating film has an energy band gap wider than the intervening film; and

a gate electrode formed on said gate insulating film

16. A field effect semiconductor device as in claim 15 wherein said intervening film comprises a material selected from the group consisting of amorphous silicon, silicon nitride, silicon carbide, and silicon oxide.

17. A field effect semiconductor device as in claim 15 where the thickness of said intervening film is 10-1000 angstroms.

18. A field effect semiconductor device comprising:

a crystalline semiconductor;

a channel region formed within the semiconductor where the density of hydrogen in the channel region is no greater than one atomic percent;

an intervening film formed on the channel region of said semiconductor where the intervening film has an energy gap wider than the semiconductor;

source and drain regions;

a gate insulating film formed on said intervening film located between said source and drain regions; and

a gate electrode formed on said gate insulating film.

19. A field effect semiconductor device as in claim 18 wherein said intervening film comprises a material selected from the group consisting of amorphous silicon, silicon nitride, silicon carbide, and silicon oxide.

20. A field effect semiconductor device as in claim 18 where the thickness of said intervening film is 10-1000 angstroms.

21. A transistor comprising:

a substrate having an insulating surface;

a crystalline semiconductor layer comprising silicon formed on said surface;

a channel region formed within said semiconductor layer; and

a gate electrode formed adjacent to said channel region with a gate insulator therebetween;

wherein an intervening film is formed between said channel region and the gate insulator where the intervening film has an energy gap wider than said channel region; and

wherein the gate insulator has an energy gap wider than the intervening film.

22. The transistor of claim 21 wherein said intervening film comprises a material selected from the group consisting of amorphous silicon, silicon nitride, silicon carbide, and silicon oxide.

23. The transistor of claim 22 wherein said silicon nitride is expressed by Si₃ N_1-3.

24. The transistor of claim 22 wherein said silicon carbide is expressed by SiC[0.2-0.7]₀.2-0.7.

25. The transistor of claim 22 wherein said silicon oxide is expressed by SiO₀.5-1.5.