Semiconductor device having an annular region for improved voltage

Abstract

The breakdown voltage of a p-n junction operated under reverse bias in at least one mode of operation of a semiconductor device is increased by providing at least one annular region forming an auxiliary p-n junction within the spread of a depletion layer from the reverse-biased junction. A passivating dielectric layer with an overlying electrically resistive layer extends over the semiconductor body surface between the active device region forming the p-n junction and a surrounding region of the body portion located beyond the (outer) annular region. The resistive layer is connected to these regions but is insulated from the annular regions by the dielectric layer. A stable high breakdown voltage can be obtained by providing the resistive layer with conductive connection means at the or each annular area which overlies the annular region(s). The conductive connection means, which may be for example annular metal areas or annular highly-doped parts of the resistive layer, is more highly conductive than the resistance of adjacent parts of the resistive layer and provides an electrical connection between these adjacent parts so that a potential variation which corresponds approximately with that along the underlying semiconductor body surface (including the annular regions) can be obtained along the resistive layer.