Patent ID: 6885082

Claim:
A semiconductor device having a bipolar transistor constructed such that a zener diode is serially build into a base, and comprising: a first conductivity type semiconductor layer that serves as a collector region; a base region of a second conductivity type provided to said first conductivity type semiconductor layer; an emitter region of said first conductivity type provided within said base region; a base electrode connection region of said first conductivity type provided to said base region; a base electrode provided so as to be electrically connected to said base electrode connection region: a zener voltage control diffusion region of said second conductivity type and provided around a periphery of said base electrode connection region so as to form a pn junction and undergo zener breakdown at a desired voltage, wherein the zener voltage control diffusion region is highly doped and is isolated electrically from the base electrode connection region; and an emitter electrode and a collector electrode provided so as to be electrically connected to said emitter region and said collector region, respectively, wherein the base electrode connection region extends into the base region at a first depth and the zener voltage control diffusion region extends into the base region at a second depth less than the first depth.