Patent ID: 6528861
Filing Date: 2003-03-04
Classification: H01L

Abstract:
A bipolar transistor structure formed in a semiconductor substrate that includes a substrate active device region having a dielectric isolation structure formed at the periphery of the active device region, the bipolar transistor structure comprising:a collector region having a first conductivity type formed in the active device region; a silicon-germanium (SiGe) epitaxial layer formed on the collector region such that an upper surface of the SiGe epitaxial layer is substantially coplanar with an upper surface of the dielectric isolation structure, the SiGe epitaxial layer defining a base region a pad of dielectric material that extends from an edge of the dielectric isolation structure over a first portion of the base region such that a second portion of the base region is exposed; forming a polysilicon emitter region having the first conductivity type, the polysilicon emitter region including a ridge that extends beyond an edge of the pad of dielectric material, the ridge being in contact with the base region such that an emitter-base junction is defined in the base region; and a silicon nitride sidewall spacer defined at an edge of the ridge and spaced-apart therefrom by intervening silicon oxide.