Patent ID: 6844575

Claim:
A method for fabrcating a heterojunction bipolar transistor, comprising the steps of: laminating a collector layer, a base layer and an emitter layer in this order on a top surface side of a semiconductor substrate; patterning the collector layer, the base layer and the emitter layer so that an area of an upper layer is smaller than an area of a lower layer, among the collector layer, the base layer and the emitter layer; forming a surface electrode for ohmic contact on each surface portion of the collector layer, the base layer and the emitter layer; forming a first via hole which extends through the emitter layer, the base layer and the collector layer and ends at the specified depth within the substrate; forming a metal wiring line which extends from the surface electrode of the emitter layer to within the first via hole so as to reach a bottom portion of the first via hole; polishing a rear surface side of the substrate up to the bottom portion of the first via hole; and providing a heat sink layer made of a metal on the polished rear surface of the substrate so that the heat sink layer makes contact with the metal wiring line within the first via hole.