Insulated gate type bipolar-transistor

摘要

An insulated gate type bipolar-transistor (IGBT) incorporates an excess voltage protecting function and drain voltage fixing function in a monolithic structure. Impurity concentration ND and the thickness of an n. sup.- type drain layer (3) is set so that a depletion region propagating from a p type base layer (7) reaches a p.sup.+ type drain layer at a voltage (V.sub.DSP) lower than a voltage (V.sub.DSS) at which avalanche breakdown is caused within the IGBT element when voltage is applied between the source and the drain.