Method for fabricating a bipolar junction transistor exhibiting improved beta and punch-through characteristics

摘要

A bipolar transistor having an emitter, a base, and a collector includes an intrinsic base region having narrow side areas and a wider central area. The side areas are located adjacent to the extrinsic base region, while the central area is disposed underneath the emitter. The lateral doping profile of the base is tailored so that the doping concentrations in the extrinsic region and the central area are relatively high compared to the doping concentration of the narrow side areas of the intrinsic base. The combination of the narrow side areas and the lateral base doping profile constrains the depletion region within the base thereby lowering punch-through voltage of the transistor without loss of beta.