Method of fabricating semiconductor device by forming doped regions that limit width of the base

摘要

A first semiconductor region is of a first conduction type and forms a transistor collector. A second semiconductor region is of a second conduction type and forms a transistor base. The second semiconductor region extends in the first semiconductor region. A third semiconductor region is of the first conduction type and forms a transistor emitter. The third semiconductor region extends in the second semiconductor region. A fourth semiconductor region is of the first conduction type and has a first portion and a second portion. The first portion extends in a part of the first semiconductor region below an edge of the third semiconductor region, and the second portion extends from the first semiconductor region into a part of the second semiconductor region outward of the edge of the third semiconductor region to limit a width of the transistor base.