Patent ID: 8101484

Claim:
A method of forming a field effect transistor, comprising: providing a substrate of a first conductivity type silicon; forming a substrate cap region of the first conductivity type silicon such that a junction is formed between the substrate cap region and the substrate; forming a body region of a second conductivity type silicon such that a junction is formed between the body region and the substrate cap region; forming a trench extending through at least the body region; and forming a source region of the first conductivity type in an upper portion of the body region, wherein during one or more temperature cycles, dopants of the first conductivity type in the substrate cap region out-diffuse into a lower portion of the body region to thereby form an out-diffusion region of the first conductivity type in the lower portion of the body region such that a spacing between the source region and the substrate out-diffusion region defines a length of a channel region of the field effect transistor.