| 摘要 |
In an element formation region, a surface of an N<-> epitaxial layer is inclined upward from an end of a field oxide film to a sidewall of an opening. An external base diffusion layer formed on the surface of the N<-> epitaxial layer is inclined upward from a side of the field oxide film to the sidewall of the opening, and is exposed at the sidewall of the opening. A portion of the sidewall of the opening exposing the external base diffusion layer is tapered. A depth of a lower end of the external base diffusion layer on the sidewall of the opening is substantially equal to or smaller than that of a bottom of the opening. With this, decrease in breakdown voltage between an emitter and a base is suppressed, and decrease and variation of a current gain hFE is suppressed.
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