Patent ID: 6972443

Claim:
A bipolar transistor, comprising: a collector region; an intrinsic base layer overlying said collector region, said intrinsic base layer including a single-crystal semiconductor; an emitter disposed within a first opening overlying said intrinsic base layer; a raised extrinsic base, including: a raised extrinsic base layer overlying said intrinsic base layer; and a link-up region electrically connecting said raised extrinsic base layer to said intrinsic base layer, said link-up region self-aligning said raised extrinsic base to said emitter, said link-up region disposed in a second opening oriented in a vertical direction substantially perpendicular to said intrinsic base layer and separate from said first opening and in an undercut region extending horizontally outward from said second opening below said raised extrinsic base layer in a first direction towards said emitter.