Patent ID: 8704302

Claim:
A power semiconductor device, comprising: a first-conductivity-type semiconductor substrate, and at least one second-conductivity-type epitaxial layer overlying and forming a junction with said substrate; at least one trench, extending downwardly into said epitaxial layer, which has dielectric material therein, and also includes vertically graded spatially fixed net electrostatic charge which tends to deplete adjacent second-conductivity-type semiconductor material; a semiconductor drift region, in said epitaxial layer, which extends down to said junction, and which has a dopant concentration which generally decreases with depth, EXCEPT that an additional concentration of said second-conductivity type dopants is present in said drift region at said junction; a semiconductor source region, which has said first conductivity type, and a semiconductor body region which has said second conductivity type and which separates said source region from said drift region; and at least one gate electrode which controls accumulation or depletion of a portion of said body region to thereby define a channel region therein; wherein, under at least some conditions, majority carriers pass from said source, through said channel and through said drift region to said substrate.