Patent ID: 8133781

Claim:
A method of forming a semiconductor structure comprising: forming a mask layer over a semiconductor substrate, wherein the semiconductor substrate is a semiconductor-on-insulator (SOI) substrate including a bottom semiconductor substrate, a buried insulator layer, and a top semiconductor substrate; forming an opening in said mask layer by patterning said mask layer; extending the opening through the top semiconductor substrate stopping on the buried insulator layer of the SOI substrate; implanting first dopant ions of a first polarity through said opening and said buried insulator layer into a first portion of the bottom semiconductor substrate of said semiconductor substrate, whereby a first doped region is formed underneath said opening; forming a trench through a portion of said first doped region by an anisotropic etch, wherein said trench extends downward from said opening through the buried insulator layer into the bottom semiconductor substrate; and implanting second dopant ions of a same polarity as the first polarity through a bottom surface and sidewall surfaces of said trench into a second portion of the bottom semiconductor substrate of said semiconductor substrate, wherein a second doped region is formed underneath said first doped region such that said second doped region and said first doped region are contiguous with each other.