| 摘要 |
After a formation of a side wall of silicon nitride on an inner periphery defining an emitter hole passing through a silicon nitride layer and a heavily doped polysilicon base electrode layer, a silicon oxide layer on a collector region is isotropically etched so as to expose an upper surface of the collector region and a bottom surface of an inner peripheral portion of the heavily doped polysilicon base electrode layer, and a ring-shaped hollow space beneath the polysilicon base electrode layer is filled with a piece of polysilicon so that the dopant impurity is diffused from the doped polysilicon layer independently from a selective growth of a base layer over the collector region.
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