ACCUFET with Schottky source contact

1. An integrated MOSgated power semiconductor device comprising:

a graded drift region of one conductivity;

a base region of said one conductivity above said drift region, said base region distinct from said drift region;

a source region of said one conductivity above said base region;

an insulated gate adjacent said base region;

an insulated source field electrode adjacent said drift region;

a source contact making ohmic contact with said source region and Schottky contact with said base region;

a substrate of the same conductivity as said drift region, wherein said drift region is formed over said substrate; and

a drain contact electrically connected to, said substrate.

2. A device according to claim 1 ,

wherein said insulated source field electrode and said insulated gate are disposed in a common trench.

3. A device according to claim 2 , wherein said insulated source field electrode includes a source field electrode comprised of a conductive material, and an insulation body interposed between said source field electrode and said drift region.

4. A device according to claim 3 , wherein said conductive material is comprised of conductive polysilicon.

5. A device according to claim 3 , wherein said insulated gate includes a gate insulator and a gate electrode, said gate insulator being interposed between said base region and said gate electrode, and said insulation body being thicker than said gate insulator.

6. A device according to claim 1 , further comprising a recess extending to a depth below said source region and terminates in said base region, wherein said source contact makes Schottky contact with said base region inside said recess.

7. A device according to claim 6 , wherein said recess is spaced from said insulated gate.

8. A device according to claim 7 , wherein said recess is adjacent an insulated source field electrode.

9. An integrated MOSgated power semiconductor device comprising:

an accumulation mode FET having an insulated gate, a graded drift region, a source contact and a base region, said base region distinct from said drift region, an insulated source field electrode adjacent said drift region; and

a Schottky diode, said Schottky diode being formed by a Schottky contact between said source contact and said base region.

10. A device according to claim 9 ,

wherein said insulated source field electrode and said insulated gate are disposed in a common trench.

11. A device according to claim 9 , further comprising a recess extending to a depth below said source region and terminates in said base region, wherein said source contact makes Schottky contact with said base region inside said recess.