A semiconductor device comprises: an extrinsic base region; a first dielectric spacer on at least a part of a sidewall of the extrinsic base region adjacent to an emitter window region; an intrinsic base region; a base link region coupling the intrinsic base region and the extrinsic base region; a collector region underlying the intrinsic base region and having a periphery underlying the base link region; and a second dielectric spacer, separating the base link region from at least the periphery of the collector region; wherein said second dielectric spacer extends laterally beyond said first dielectric spacer to underlie said emitter window region.