Semiconductor device with guard ring and Zener diode layer thereover

摘要

A semiconductor device includes a polysilicon diode layer formed so that pn junctions are positioned only in a portion (first portion) of the polysilicon diode layer which overlies at least one guard ring having a field alleviating structure for holding the breakdown voltage of an IGBT, thereby to prevent the deterioration of the breakdown voltage of the polysilicon diode resulting from the operation of a MOSFET including the pn junctions of the polysilicon diode layer between the collector and gate of the IGBT, an n- drift layer and a field oxide film.