Patent ID: 7279378

Claim:
A process of fabricating a semiconductor device comprising: providing a semiconductor substrate of a first conductivity type, the substrate not containing an epitaxial layer; forming a first mask on a surface of the substrate, said first mask having a first opening, said first opening having a first lateral dimension; implanting a dopant of a second conductivity type through the first opening to form a first deep layer; forming a second mask on the surface of the substrate, said second mask having a second opening, said second opening having a second lateral dimension, said second lateral dimension being entirely enclosed within said first lateral dimension; and implanting dopant of the first conductivity type through the second opening to form a second deep layer, said second deep layer being laterally constrained within said first deep layer, wherein the straggle of the implant of dopant of the first conductivity type is greater than the straggle of the implant of dopant of the second conductivity type such that the second deep layer overlaps and extends above and below the first deep layer and upper boundaries of said first and second deep layers are located below said surface of said substrate.