Patent ID: 8802532

Claim:
A method for manufacturing a bipolar transistor, the method comprising: etching a portion of a semiconductor substrate to form a trench, using an etching mask exposing a portion of the semiconductor substrate; forming a first epitaxial layer on the surface of the trench through an epitaxial process using first conduction type impurity ions to form a first collector; forming a second collector into the semiconductor substrate adjacent to the first epitaxial layer by diffusion of the first epitaxial layer; forming a first spacer on the inner wall of the first epitaxial layer; forming a second epitaxial layer to form a third collector, wherein the second epitaxial layer is formed over the first epitaxial layer and inside the first spacer, wherein the second epitaxial layer is formed through an epitaxial process over the first epitaxial layer exposed by the first spacer; forming an extrinsic base on the inner wall of the first spacer, wherein said forming the extrinsic base includes forming a second conduction type polysilicon film on the entire surface of the semiconductor substrate in which the first spacer is formed and performing an anisotropic dry etching process on the second conduction type polysilicon film to form the extrinsic base on the inner wall of the first spacer; forming an insulating film over the entire surface of the semiconductor substrate, in which the extrinsic base is formed; performing an ion implantation process using second conduction type impurity ions to form an intrinsic base in the second epitaxial layer; etching the insulating film to form a second spacer on the inner wall of the extrinsic base; and forming an emitter inside the second spacer.