Patent ID: 8084811

Claim:
A method for forming a power device, comprising: forming an epitaxial layer on a substrate material; selectively removing a portion of the epitaxial layer to form a column extending from the substrate material, the column having a sidewall; forming an insulation material on the sidewall of the column; and diffusing a dopant into the sidewall of the column via the insulation material, wherein: forming an epitaxial layer includes forming an n-type epitaxial layer on an n-type substrate material; the insulating material is a first insulation material having a first thickness; the method further includes forming a second insulation material onto an exposed surface of the column, the second insulation material having a second thickness greater than the first thickness, wherein the first and second insulation materials include at least one of silicon dioxide, spin-on glass, and flowable oxide; selectively removing a portion of the epitaxial layer includes: depositing a photoresist onto the second insulation material; patterning the deposited photoresist to form an opening in the photoresist; removing material from the second insulation material and the epitaxial layer via the opening; and diffusing a dopant includes: depositing a polysilicon material on the first and second insulation materials, the polysilicon being doped with a p-type dopant; and diffusing the p-type dopant of the polysilicon into the sidewall of the column via the first insulation material while the second insulation material prevents the p-type dopant from diffusing into the surface of the column.