Self-aligned bipolar transistor structure

A bipolar transistor structure formed in a semiconductor substrate having a first conductivity type, the bipolar transistor structure comprising:

• a collector region having a second conductivity type that is opposite the first conductivity type and that is formed in a substrate active device region defined by isolation dielectric material formed in an upper surface of the semiconductor substrate;
• an epitaxial layer having a monocrystalline portion formed over the collector region and a polycrystalline region formed over the isolation dielectric material;
• a sloped in-situ doped emitter plug having the second conductivity type formed on the epitaxial layer, the sloped in-situ doped emitter having an upper surface area having a first width and a lower surface area having a second width that is less than the first width wherein the sidewalls of the sloped in-situ emitter plug are continuously sloped from the upper surface to the lower surface;
• dielectric spacer material formed on sidewalls of the sloped in-situ doped emitter to provide an emitter structure such that the emitter structure may be utilized to introduce dopant having the first conductivity type into portions of the epitaxial layer.