Field effect semiconductor device having improved voltage breakdown characteristics

Claim 1

A semiconductor device comprising a semiconductor body having a major surface, a comparatively weakly-doped semiconductor region of a first conductivity type adjoining said major surface, several first zones of a second conductivity type opposite to the first conductivity type also adjoining said major surface, said first zones being arranged at a regular distance "d" from each other and extending from the major surface down to a smaller depth in the semiconductor body than the depth of the semiconductor region, a comparatively highly-doped second zone of the first conductivity type inside each first zone which is separated in the semiconductor body by the first zone from the semiconductor region, each first zone having a first outer edge and each second zone having a second outer edge, the second outer edge, viewed on the main surface, being located inside the first outer edge and the first and the second outer edges being substantially equidistant throughout their lengths, each second zone being connected to the adjoining first zone, a substantially symmetrical grid-shaped part of the semiconductor region which separates the first zones from each other at the major surface and surrounds each of the first zones, an insulating layer for covering the grid-shaped part at the major surface, said insulating layer extending beyond the first outer edge and at least as far as the second outer edge, a conductive layer on the insulating layer which serves as a gate electrode and covers at least part of the major surface occupied by the grid-shaped part, said conductive layer having openings whose sizes correspond to the later extent of the first zones located beneath these openings in the semiconductory body, and further surface zones of the second conductivity type provided at the major surface in the grid-shaped part at intermediate spaces thereof bounded by three or more first zones, said further zones being electrically isolated from said gate electrode and filling substantially all of said intermediate spaces which are located at a distance of at least half said regular distance "d" from said first zones, and the conductive layer being provided with further openings above the further surface zones whose sizes correspond to the lateral extent of the further surface zones.