Patent ID: 8441084

Claim:
A heterojunction bipolar transistor (HBT) structure comprising: a substrate including a buried insulator layer; a base contacting a top surface of said buried insulator layer and including single crystalline germanium having a doping of a first conductivity type; an emitter contacting said top surface of said buried insulator layer and laterally contacting said base and comprising doped polysilicon having a doping of a second conductivity type that is the opposite of said first conductivity type; an extrinsic base contacting a center portion of a top surface of said base and comprising a polycrystalline semiconductor material having a doping of said first conductivity type; and a dielectric spacer laterally surrounding said extrinsic base and contacting a peripheral portion of said top surface of said base, wherein a vertical interface between said emitter and said base is vertically coincident with an outer sidewall of said dielectric spacer.