Patent ID: 8004039

Claim:
A metal-oxide-semiconductor (MOS) transistor, comprising: a body region of a first conductivity type formed in a semiconductor layer; a conductive gate formed on a first surface of the semiconductor layer and insulated from the semiconductor layer by a gate dielectric layer; a source region of a second conductivity type formed in the body region of the semiconductor layer on one side of the conductive gate, a part of the source region extending underneath the conductive gate; a heavily doped source contact diffusion region of the second conductivity type formed in the source region, the source contact diffusion region forming the source terminal of the MOS transistor; a lightly doped drain region of the second conductivity type formed in the body region of the semiconductor layer on the opposite side of the conductive gate, the lightly doped drain region being a drift region of the MOS transistor and a part of the lightly doped drain region extending underneath the conductive gate; a heavily doped drain contact diffusion region of the second conductivity type formed in the lightly doped drain region, the drain contact diffusion region forming the drain terminal of the MOS transistor; and an insulating trench formed in the lightly doped drain region adjacent the drain terminal, the insulating trench blocking a surface current path in the drift region thereby forming vertical current paths in the drift region around a bottom surface of the trench, wherein the insulating trench comprises a dielectric sidewall and the conductive gate extends into and filling remaining portion of the trench, the dielectric sidewall having a thickness greater than the gate dielectric layer.