Patent ID: 8247329

Claim:
A method for forming a semiconductor device comprising: providing a heavily doped semiconductor substrate of a first conductivity type; forming a semiconductor layer of a second conductivity type on the heavily doped semiconductor substrate; forming a plurality of trenches in the semiconductor layer, the trenches extending close to, up to, or into the semiconductor substrate, the trenches forming mesas in the semiconductor layer; forming by epitaxial growth a first epitaxial layer of the first conductivity type on the semiconductor layer covering at least sidewalls of the trenches; forming a first dielectric layer in the trenches, the first dielectric layer filling at least part of the trenches; forming a gate dielectric layer on the sidewalls of a first trench above the first dielectric layer and adjacent to the first epitaxial layer; and forming a gate conductive layer in the first trench, the gate conductive layer being formed above the first dielectric layer and adjacent the gate dielectric layer, wherein the first epitaxial layer is disposed along the sidewalls of the trenches and has uniform doping concentration, the first epitaxial layer having a first thickness and a first doping concentration and a mesa of the semiconductor layer having a second thickness and a second doping concentration, the first and second thicknesses and the first and second doping concentrations being selected to achieve charge balance in operation.