A semiconductor device includes a heterojunction bipolar transistor and a junction gate type field effect transistor which are formed on a semiconductor base. A base region and graft base regions of the heterojunction bipolar transistor, and a channel region and source/drain regions of the junction gate...http://www.google.es/patents/US5912479?utm_source=gb-gplus-sharePatente US5912479 - Heterojunction bipolar semiconductor device
