| 摘要 |
In accordance with the above first embodiment of the present invention, after a base polysilicon film has been grown, a lump anneal is carried out because of an extremely small variation to the silicon dioxide film. Subsequently, a buffered fluorine acid is used which has a large selective etching ratio of the silicon oxide film to the polysilicon film to side-etch the silicon oxide film in the horizontal direction by a predetermined width before the base impurity BF2+ is implanted and then the emitter polysilicon film is formed. For those reasons, a variation in distance between the n+-substrate and a collector is small. The base width "WB" of the base region is not varied, whereby variations in high frequency performance of the bipolar transistor are suppressed.
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