| 摘要 |
PURPOSE:To prevent generation of facets and voids in a cavity formed by side etching an oxide film, and realize reduction of a base resistance and miniaturization of an element. CONSTITUTION:A buried layer 2, an N<-> type epitaxial layer 3 turning to a collector layer, and a field oxide film 4 are formed on a silicon substrate 1. An oxide film 6, a P<+> type polycrystalline Si layer 7, and a nitride film 8 are deposited. An emitter aperture is formed by selectively etching the nitride film 8 and the Si layer 7. After a side wall 9 is formed by using the nitride film, the oxide film 6 is etched by a wet method, and a cavity is formed under the Si layer 7. Polycrystalline silicon 10 is buried in the cavity by deposition of polycrystalline Si 10 and etching (a). A P-type epitaxial base layer 11 is formed (b). An N<+> emitter electrode polycrystalline Si layer 13 is formed (c). An emitter layer is formed by heat treatment.
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