US Patent 7442617 Method for manufacturing bipolar transistor

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