Patent ID: 7935986
Filing Date: 2011-05-03
Classification: H01L

Abstract:
1. A transistor comprising: a substrate; a trench isolation structure in said substrate and positioned laterally adjacent to a collector region; an emitter cap layer on said substrate above said collector region without extending laterally over said trench isolation structure; an extrinsic base comprising a polycrystalline semiconductor layer adjacent to said emitter cap layer and extending laterally over said trench isolation structure, said polycrystalline semiconductor layer having an upper surface; a first dielectric layer above and abutting said upper surface of said polycrystalline semiconductor layer; a first opening, having a first sidewall, extending vertically through said first dielectric layer to said upper surface of said polycrystalline semiconductor layer; a second opening aligned below said first opening, said second opening having a second sidewall and extending vertically through said polycrystalline semiconductor layer to said emitter cap layer, said first opening being wider than said second opening; a first dielectric spacer within said first opening positioned laterally adjacent to said first sidewall, said first dielectric spacer being above and abutting said upper surface of said polycrystalline semiconductor layer; an emitter having a lower section and an upper section, a second dielectric layer comprising an L-shaped dielectric layer, said L shaped dielectric layer comprising: a second dielectric spacer on said horizontal portion and positioned laterally between said vertical portion and said lower section of said emitter.