Patent ID: 6838350

Claim:
A method for fabricating a bipolar transistor, comprising: forming a first region of a first conductivity type in a semiconductor structure to form a collector region of the bipolar transistor; forming a second region of a second conductivity type in the first region to form a base region of the bipolar transistor; applying a first mask over the semiconductor structure, the first mask including an opening defining an emitter region of the bipolar transistor; using the first mask, forming a third region of the first conductivity type in the semiconductor structure, the third region being formed in the first region and overlying the second region; using the first mask, forming a fourth region of the second conductivity type in the semiconductor structure, the fourth region being formed in the second region and more heavily doped than the second region, a lower portion of the fourth region being overlaid by the third region; and using the first mask, forming a fifth region of the first conductivity type in the semiconductor structure, the fifth region being formed in the second region and above the fourth region as the emitter region of the bipolar transistor.