Abstract: A circuit structure contains at least one bipolar transistor whose emitter is fashioned as a part of a doped silicon layer grown on a substrate. The doped silicon layer comprises a sidewall extending parallel to its surface normal, the sidewall being covered with a doped silicon structure in contact with the silicon substrate and forms the base of the bipolar transistor. The bipolar transistor comprises a self-aligned, effective emitter with a 50-500 nm.

Abstract: A thin film semiconductor gas sensor including a metal oxide semiconductor sensor layer whose electrical resistance changes in dependence upon the nature and concentration of a gas being detected and having a heating element integrated therewith is improved by forming the sensor from a semiconductor body having a shell zone located relatively close to an outer surface of such body and being doped to the point of degeneration, with two spaced apart metal contact strips being positioned on such doped shell zone for connection with a current source to heat the sensor.