Semiconductor device having a trench structure and method for manufacturing the same

1. A semiconductor device, comprising:

a which is which is formed of a high resistance first conductivity type semiconductor at a predetermined depth from a surface of a semiconductor substrate;

a plurality of trenches extending from a surface to a midway depth of the well region;

a gate insulating film formed on surfaces of a concave portion and a convex portion formed by each of the trenches;

a first gate electrode embedded inside the trenches;

a second gate electrode formed on the surface of the semiconductor substrate in contact with the first gate electrode in regions of the concave portion and the convex portion, the regions excluding vicinities of both ends of the trenches;

a third gate electrode embedded inside the trenches in the vicinities of the both ends of the trenches in contact with the first gate electrode and the second gate electrode so that a surface of the third gate electrode is located at a position deeper than the surface of the semiconductor substrate; and

a source region and a drain region formed as low resistance second conductivity type semiconductor layers from a part of a surface of the high resistance first conductivity type semiconductor that is out of contact with the third electrode so that the source and drain regions are formed electrode, so as to be deeper in a side surface of the concave portion of each of the trenches than in the surface of the convex portion of each of the trenches and shallower than the depth of the well region.

2. A semiconductor device according to claim 1 , wherein the third gate electrode is omitted.

3. A semiconductor device according to claim 2 , wherein each of the source region and the drain region has an upper surface located at a position lower than an uppermost surface of the gate insulating film.

4. A semiconductor device according to claim 2 , wherein each of the source region and the drain region has a light doped drain (LDD) structure.

5. A semiconductor device according to claim 2 , wherein the each of the source region and the drain region has a double diffused drain (DDD) structure.

6. A semiconductor device according to claim 2 , wherein each of the source region and the drain region has a lateral double diffused metal oxide semiconductor (LDMOS) structure.

7. A semiconductor device according to claim 2 , wherein a width of the convex portion of each trench is approximately 1,000 Å.

8. A semiconductor device according to claim 2 , wherein the well region is formed using a twin well technique.

9. A semiconductor device according to claim 2 , wherein the semiconductor substrate has the first conductivity type.

10. A semiconductor device according to claim 2 , wherein the semiconductor substrate has the second conductivity type.

11. A semiconductor device according to claim 1 , wherein each of the source region and the drain region has a light doped drain (LDD) structure.

12. A semiconductor device according to claim 1 , wherein the each of the source region and the drain region has a double diffused drain (DDD) structure.

13. A semiconductor device according to claim 1 , wherein each of the source region and the drain region has a lateral double diffused metal oxide semiconductor (LDMOS) structure.

14. A semiconductor device according to claim 1 , wherein a width of the convex portion of each trench is approximately 1,000 Å.

15. A semiconductor device according to claim 1 , wherein the well region is formed using a twin well technique.

16. A semiconductor device according to claim 1 , wherein the semiconductor substrate has the first conductivity type.

17. A semiconductor device according to claim 1 , wherein the semiconductor substrate has the second conductivity type.

18. A semiconductor device according to claim 1 , wherein a width of the convex portion of each trench is approximately 1,000 Å.

19. A method of manufacturing a semiconductor device, comprising:

forming a well region of a high resistance first conductivity type semiconductor at a predetermined depth from a surface of a semiconductor substrate;

forming a plurality of trenches which extend from a surface to a midway depth of the well region;

forming a gate insulating film on surfaces of a concave portion and a convex portion formed by each of the trenches;

depositing a gate electrode material inside the trenches and on the surface of the semiconductor substrate;

etching the gate electrode material to form:

a first gate electrode which is embedded inside the trenches;

a second gate electrode which is formed on the surface of the semiconductor substrate in contact with the first gate electrode in regions of the concave portion and the convex portion, the regions excluding vicinities of both ends of the trenches; and

a third gate electrode which is embedded inside the trenches in the vicinities of the both ends of the trenches in contact with the first gate electrode and the second gate electrode so that a surface of the third gate electrode is located at a position deeper than the surface of the semiconductor substrate; and

forming, by a multi-direction oblique ion implantation method, a source region and a drain region as low resistance second conductivity type semiconductor layers from a part of a surface of the high resistance first conductivity type semiconductor that is out of contact with the third gate electrode so that the source and drain regions are deeper in a side surface of the concave portion of each of the trenches than in the surface of the convex portion of each of the trenches and shallower than the depth of the well region.

20. A method of manufacturing a semiconductor device according to claim 19 , further comprising etching the surface of the high resistance first conductivity type semiconductor in the source region and the drain region at the same time as the etching of the gate electrode material.