Bipolar device having a monocrystalline semiconductor intrinsic base to extrinsic base link-up region

Abstract

Disclosed are bipolar devices, which incorporate an entirely monocrystalline link-up region between the intrinsic and extrinsic base layers, and methods of forming the devices. In the methods, a selective epitaxial deposition process grows monocrystalline semiconductor material for the extrinsic base layer on an exposed edge portion of a monocrystalline section of an intrinsic base layer. This deposition process is continued to intentionally overgrow the monocrystalline semiconductor material until it grows laterally and essentially covers a dielectric landing pad on a center portion of that same monocrystalline section of the intrinsic base layer. Subsequently, an opening is formed through the extrinsic base layer to the dielectric landing pad and the dielectric landing pad is selectively removed, thereby exposing monocrystalline surfaces only of the intrinsic and extrinsic base layers. A semiconductor layer is then formed by epitaxial deposition on the exposed monocrystalline surfaces, thereby forming the entirely monocrystalline link-up region.