Patent ID: 8642427

Claim:
A method for fabricating a semiconductor device, comprising: providing a semiconductor substrate of a first conductivity type; forming an epitaxial layer of the first conductivity type on the semiconductor substrate; forming a plurality of first trenches in the epitaxial layer; forming a first doped region of the first conductivity type in the epitaxial layer and surrounding each first trench; forming a second doped region of the first conductivity type in each first doped region and adjacent to each first trench; filling each first trench with a first insulating material; forming a plurality of second trenches in the epitaxial layer and in an alternate arrangement with the plurality of first trenches; forming a third doped region of a second conductivity type in the epitaxial layer and surrounding each second trench; and filling each second trench with a second insulating material, wherein the first doped region comprises a first dopant and the second doped region comprises a second dopant, and the first dopant has diffusivity larger than that of the second dopant.