Patent ID: 8258575

Claim:
A lateral MOSFET comprising: a semiconductor substrate of a first conductivity type, the substrate not comprising an epitaxial layer; a gate formed atop a gate dielectric layer over a surface of the substrate; a drain region of a second conductivity type opposite to the first conductivity type formed in the substrate, the drain region being located adjacent the surface of the substrate on one side of the gate; a drift region of the second conductivity type formed in the substrate, the drift region having a doping concentration less than a doping concentration of the drain region, the drift region being located adjacent the drain region and laterally surrounding the drain region; a source region of the second conductivity type formed in the substrate, the source region being located adjacent the surface of the substrate on a side of the gate opposite to the drain region, the source region laterally surrounding the drain region; a body region of the first conductivity type formed in the substrate, the body region having a doping concentration greater than a doping concentration of the substrate, the body region being located adjacent the source region and extending under the gate, a portion of the substrate separating the drift region from the body region; a trench extending downward from the surface of the substrate laterally surrounding the source region, the trench being filled with a dielectric material; and a sidewall region of the second conductivity type extending downward into the substrate from a bottom of the trench.