Patent ID: 7091573

Claim:
A power transistor having at least one trench transistor cell in a semiconductor body, comprising: a drain zone, a drift zone, a channel zone, and a source zone formed in each case successively and substantially horizontally in the semiconductor body; the semiconductor body having a trench formed therein with a base and a defined body height opposite a pn junction between said drift zone and said channel zone; a first dielectric layer cladding said trench substantially to said body height, and a gate oxide cladding said trench between said body zone and a semiconductor body surface; and a field electrode extending in said trench substantially from said trench base to an upper edge of said first dielectric layer, said field electrode being connected to be at a fixed potential or at a source potential; a gate electrode disposed substantially between said body height and the semiconductor body surface, said gate electrode being electrically insulated from the semiconductor body by said gate oxide and having a lower edge with a profile, said profile having a horseshoe shape with two jaws projecting at edges thereof and a center between said jaws having an inward bulge in which said field electrode enters beyond said pn junction; and a second dielectric layer formed between said gate electrode and said field electrode.