Method for fabricating a bipolar transistor with a base layer having an extremely low resistance

摘要

A base region structure involved in a bipolar transistor, wherein the base region comprises a compound semiconductor epitaxial layer formed in a recessed portion provided by etching in an upper region of the semiconductor substrate and the recessed portion has a depth corresponding to a thickness of the compound semiconductor epitaxial layer so that the base region has a top surface positioned at the same level as a top surface of the semiconductor substrate.