Power MOSFET with improved avalanche resistance

Claim 1

A power MOSFET, comprising: a semiconductor body having an edge, a plurality of cells disposed on said semiconductor body and being connected in parallel, each of said cells including a gate zone and a source zone embedded in planar fashion in said gate zone; said source zones having contact holes of a given contact hole depth formed therein; said gate zones having a given conductivity type, a given depth and a given doping concentration; a metallization layer contacting said gate zones through said contact holes formed in said source zones; gate electrodes being mutually connected in parallel; an annular zone formed in said semiconductor body between said cells and said edge of said semiconductor body, said annular zone having said given conductivity type; said annular zone having said given depth and said given doping concentration of said gate zones; said annular zone having an annular trench formed therein; said annular trench being contacted with said metallization layer and having a depth corresponding to said given contact hole depth; and said annular zone having at least one further annular zone disposed in said annular trench at a side thereof facing away from said edge of said semiconductor body, said at least one further annular zone having a conductivity type corresponding to a conductivity type of said source zones and having the same depth and the same doping concentration as said source zones; an insulating layer covering said semiconductor body between said annular trench and said edge of said semiconductor body, and a conducting layer covering said insulating layer, said conducting layer being formed from the same material as said gate electrodes.