| 摘要 |
A method for fabricating a bipolar transistor improves the fast characteristics of the transistor at low operating voltages. An oxide film is formed on a semiconductor substrate, in which a buried layer is formed, and a floating poly base is formed on the oxide film. An insulating film is then formed on the entire surface of the semiconductor substrate including the floating poly base. The insulating film and the floating poly base are etched to define a base region and a collector region, and a first epitaxial layer is formed in the base and collector regions, with the first epitaxial layer having a smaller thickness than the oxide film. A second epitaxial layer is formed on the first epitaxial layer, and impurities are implanted into the second epitaxial layer in the base and collector regions. A second polysilicon layer is then formed on the second epitaxial layer in the base region, and electrodes are formed on the semiconductor surface.
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