Semiconductor device having screening electrode and method

1. A semiconductor device, comprising:

a substrate having a major surface, wherein the substrate comprises a first conductivity type;

a pedestal structure formed overlying a portion of the major surface;

a conductive material disposed along a side surface of the pedestal structure to define an edge of a first conduction electrode of the semiconductor device;

a first doped region of a second conductivity type formed in the major surface adjacent the first conduction electrode, wherein a portion of the first doped region forms a channel region when the semiconductor device is in operation;

a first current carrying region of the first conductivity type formed in the first doped region; and

a screening electrode formed adjacent the major surface and in proximity to the first doped region, wherein the screening electrode comprises:

a trench formed in the major surface;

a dielectric layer formed over surfaces of the trench; and

a conductive layer formed over the dielectric layer.

2. The semiconductor device of claim 1 , wherein the substrate includes a semiconductor layer of a first conductivity type formed over the substrate, wherein the semiconductor layer has a lower doping concentration than the substrate.

3. The semiconductor device of claim 2 further comprising a second doped region of the first conductivity type formed adjacent the major surface between the first doped region and the screening electrode.

4. The semiconductor device of claim 1 , wherein the substrate comprises one of silicon-germanium, silicon-germanium-carbon, or carbon doped silicon.

5. The semiconductor device of claim 1 , wherein the conductive layer comprises polysilicon.

6. The semiconductor device of claim 5 wherein the conductive layer comprises p-type conductivity.

7. The semiconductor device of claim 5 wherein the conductive layer comprises n-type conductivity.

8. The semiconductor device of claim 1 , wherein a second surface of the substrate forms a second current carrying region.

9. The semiconductor device of claim 1 , wherein the screening electrode is coupled to the first current carrying region.

10. The semiconductor device of claim 1 , wherein the screening electrode is configured to be independently biased.

11. The semiconductor device of claim 1 , wherein the pedestal structure includes:

a first dielectric layer formed over the top surface of the substrate;

a second dielectric layer formed over the first dielectric layer; and

a conductive layer formed over the second dielectric layer, wherein the conductive layer is coupled to the conductive material.

12. A semiconductor device, comprising:

a semiconductor substrate having a semiconductor layer of a first conductivity type, wherein the semiconductor layer has a major surface;

a body region of a second conductivity type disposed in semiconductor layer for forming a channel of the semiconductor device;

a first current carrying region of the first conductivity type formed in the body region;

a gate structure formed over the top surface adjacent the channel; and

a screening electrode formed in the semiconductor layer in proximity to the body region, wherein the screening electrode comprises:

a trench formed in the major surface;

a dielectric layer formed in the trench; and

a conductive electrode formed over the dielectric layer.

13. The semiconductor device of claim 12 wherein the semiconductor layer comprises one of silicon-germanium, silicon-germanium-carbon, carbon doped silicon, or silicon carbide.

14. The semiconductor device of claim 12 , wherein the conductive electrode comprises n-type polysilicon.

15. The semiconductor device of claim 12 further comprising a pedestal structure formed over the major surface, and wherein the gate structure includes a control electrode formed along a side surface of the pedestal structure.

16. The semiconductor device of claim 12 , wherein the substrate comprises the second conductivity type.