Patent ID: 6927476

Claim:
A heterojunction bipolar transistor, comprising: a substrate including a collector layer; a semiconductor intrinsic base layer comprising a single crystal semiconductor selected from the group consisting of silicon and silicon germanium, overlying the collector layer; a raised extrinsic base layer having a bottom surface in contact with the semiconductor intrinsic base layer; an emitter layer formed on and forming a heterojunction with the semiconductor intrinsic base layer; a spacer separating the raised extrinsic base layer from the emitter layer, the spacer having a lower layer consisting essentially of an oxide, and an upper layer above the lower layer consisting essentially of a nitride, the upper layer having a first sidewall at least partially contacting the raised extrinsic base layer and a second sidewall wholly contacting the emitter layer; a base electrode conductively connected to the raised extrinsic base layer; a collector electrode conductively connected to the collector layer; and an emitter electrode conductively connected to the emitter layer.