| 摘要 |
PURPOSE:To reduce a parasitic capacity by leaving the non-oxidizable substance on the side wall of a step part of a base electrode end part by anisotropic etching and oxidizing other parts, with step followed by selective etching of that to form a minute window. CONSTITUTION:At the end part of a base electrode (polysilicon 9) formed through oxide 4 and 4' as insulating layers on a P-type semiconductor substrate 1, a step part is formed, on which an SiO2 film 17 and a polysilicon film 18a are formed by thermal oxidation and further a non-oxidizable substance layer Si3N4 film 18b is formed. Next, the film 18b is subjected to anisotropic etching to leave the non-oxidizable substance layer 18b of sidewall form on the side wall of the step part. By using that as a mask, the surface of the exposed part of the semiconductor layer 18a is subjected to thermal oxidation to form an SiO2 film 19. Then, the film 18b, the film 18a and the SiO2 film 17 are removed to form an opening which exposes a part of the semiconductor substrate. Furthermore, B ions are implanted for diffusing impurities into the semiconductor substrate to form a graft base region 7'. Then, an emitter region 8 is formed by using the insulating layer as a mask. |
