Patent ID: 7932541
Filing Date: 2011-04-26
Classification: H01L

Abstract:
1. A hetero-junction bipolar transistor structure comprising: a single crystalline semiconductor substrate having a top surface; an emitter region within said single crystalline semiconductor substrate below said top surface, said emitter region comprising a first type dopant; a single crystalline semiconductor extrinsic base layer on said single crystalline semiconductor substrate, said single crystalline semiconductor extrinsic base layer comprising a second type dopant; a first trench extending through said single crystalline semiconductor extrinsic base layer to said single crystalline semiconductor substrate and having a first sidewall and a bottom surface; a single crystalline semiconductor intrinsic base layer above said single crystalline semiconductor extrinsic base layer and further lining said first trench such that, within said first trench, a first portion of said single crystalline semiconductor intrinsic base layer is adjacent to said first sidewall and a second portion of said single crystalline semiconductor intrinsic base layer is adjacent to said bottom surface; a dielectric layer on said single crystalline semiconductor intrinsic base layer; a second trench extending through said dielectric layer to said single crystalline semiconductor intrinsic base layer, said second trench having a second sidewall approximately aligned above said first sidewall; a sidewall spacer within said second trench positioned laterally adjacent to said second sidewall and within said first trench positioned laterally adjacent to said first portion of said single crystalline semiconductor intrinsic base layer; and a collector layer comprising said first type dopant and having a single crystalline semiconductor lower portion, a mid-portion and a polycrystalline semiconductor upper portion,