Patent ID: 6897547

Claim:
A semiconductor device comprising: a low resistance semiconductor substrate; a high resistance semiconductor layer formed on said low resistance semiconductor substrate; an insulation layer formed on said high resistance semiconductor layer; a transistor element composed of a collector region, a base region, and an emitter region which are formed in said high resistance semiconductor layer; an emitter electrode formed in said insulation layer so as to be electrically connected to said emitter region; a sub-emitter electrode formed in said insulation layer electrically connected to said emitter electrode; a low resistance impurity-diffusion region formed in said high resistance semiconductor layer such that said sub-emitter electrode is electrically connected to said low resistance semiconductor substrate through said low resistance impurity-diffusion region, wherein said lower resistance impurity-diffusion region extends veritcally from said insulation layer to said low resistance semiconductor substrate, and wherein the impurity is one conductor type; a base electrode formed in said insulation layer so as to be electrically connected to said base region; and a base-bonding pad formed on said insulation layer so as to be electrically connected to said base electrode, wherein said base-bonding pad is placed on said insulation layer above said low resistance impurity-diffusion region so as to be at least partially overlapped with said low resistance impurity-diffusion region.