Low-noise bipolar transistor operating predominantly in the bulk region

摘要

A low-noise NPN transistor comprising a cut-off region laterally surrounding, at a given distance, the emitter region in the surface portion of the transistor and of such conductivity as to practically turn off the surface portion of the transistor, so that the transistor operates mainly in the bulk portion. The cut-off region is formed by a P ring astride a P.sup.- type well region and the epitaxial layer.