US Patent 7329584 Method for manufacturing bipolar transistor

A method for manufacturing a bipolar transistor includes: forming a device isolation layer on a semiconductor substrate having first and second well regions of a first conductivity therein; implanting ions of a second conductivity in the first well to form a third well; forming and patterning a conductive layer on the semiconductor substrate; forming an emitter electrode pattern on the third well region, and forming a collector electrode pattern on the second well region; forming spacers at sidewalls of the emitter and collector electrode patterns; performing a diffusion process to form an emitter region of a first conductivity on the third well region and to form a collector region of a first conductivity on the second well region; implanting ions of a second conductivity in the third well region to form a base region; and removing the emitter electrode and collector region patterns.