Method for fabricating an epitaxial base bipolar transistor with raised extrinsic base

A method for fabricating an epitaxial base bipolar transistor having a raised extrinsic base comprising the steps of:

• (a) growing a base layer comprising at least an epitaxial single crystal layer on a single crystal semiconductor substrate;
• (b) forming a mandrel on said epitaxial single crystal layer;
• (c) forming a doped polysilicon layer over the mandrel and forming superspacers from said doped polysilicon layer, said superspacers serving as a raised extrinsic base;
• (d) removing the mandrel to form a trench;
• (e) forming a raised emitter on a surface of said epitaxial single crystal layer in the trench, said raised emitter including insulating material formed on at least sidewalls thereof, said insulating material electrically isolating said raised extrinsic base from said raised emitter;
• and
• (f) diffusing dopant from the raised emitter and said raised extrinsic base so as to provide an emitter diffusion and an extrinsic base diffusion in portions of the epitaxial single crystal layer.