Patent ID: 7800135

Claim:
A vertical insulated gate field-effect transistor semiconductor device comprising: an array of cells formed in a die of semiconductor material presenting a first face and a second face opposite to said first face, with first and second superposed drain layers of a first conductivity type, the first drain layer extending from said second face and the second drain layer having a less high dopant density than said first drain layer and extending to said first face said array including basic cells and edge cells at the edges of said array, each of said basic cells comprising a source region of said first conductivity type extending from said first face a base region of the opposite conductivity type surrounding said source region at and below said first face, said base region forming with said source region and drain layers respectively a base-source junction and a base-drain junction both extending to said first face so as to define respective junction perimeters thereat, a gate electrode insulated from said die by an insulating layer and extending at said first face over at least part of said perimeters of said base-source junction and said base-drain junction at said first face, whereby to form a conductive channel in an on-state of the device in said base region between said source region and said drain layers in response to a gate voltage applied to said gate electrode; and an active drain region in said second drain layer at the first face between base regions of adjacent cells, the active drain region comprising: peripheral regions extending beside respective perimeters of said base-drain junctions not deeper than the base regions, said peripheral regions being of higher dopant density than the rest of said second drain layer and an intermediate region between the peripheral regions in the centre of the active drain region provided with a lighter dopant density than the rest of the second drain layer so as to present to source-drain current a trumpet shaped conductivity path.