Epitaxial transistor with limited area buried layer and lifetimekillers

Claim 1

A semiconductor device having a transistor, said transistor comprising a semiconductor substrate body having top and bottom major surfaces and an epitaxial layer on its top surface; said transistor further comprising a surface base region in the epitaxial layer and spaced from the substrate, a surface emitter region nested in the base region, and a collector region; said collector region comprising a part of the epitaxial layer completely surrounding the base region and extending to the epitaxial layer surface and of relatively high resistivity, a collector contact surface region of relatively low resistivity and laterally spaced from the base region, and a buried layer of relatively low resistivity and located at the epitaxial layer substrate interface and extending directly underneath the collector contact region and up to and underneath only that portion of the base region directly surrounding the emitter region such that a substantial part of the epitaxial layer extending underneath other lateral portions of the base region not directly surrounding the emitter region and the underlying epitaxial layer-substrate interface remain free of the buried layer; emitter, base, and collector connections to respectively the emitter, the base, and the collector contact regions at the epitaxial layer surface, and a carrier lifetime-reducing impurity in the substrate, the collector region and the base region, said carrier lifetime reducing impurity having been introduced into the transistor via the bottom surface of the substrate.