Patent ID: 8330214

Claim:
A power semiconductor device, comprising: a current-controlling structure, which under at least some conditions injects charge carriers into a semiconductor drift region; and at least one insulated trench, extending downwardly in proximity to said drift region, which has dielectric material therein, and also includes spatially fixed net electrostatic charge; wherein said spatially fixed net electrostatic charge, and a dopant concentration of said drift region, have respective densities which both vary vertically along the length of said trench; and wherein the ratio of said spatially fixed net electrostatic charge to said dopant concentration is higher at lower portions of said trench than at upper portions of said trench, wherein said current-controlling structure comprises a gate electrode, inside said insulated trench, which is capacitively coupled through at least one sidewall of said trench to control inversion of a semiconductor material surrounding said trench and to thereby permit passage of majority carriers through said semiconductor material in a predominantly vertical direction.