| 摘要 |
PURPOSE:To obtain a semiconductor device which is protected from degradation of a dielectric strength caused by the rising of an autodoping layer by forming the 2nd conductivity type impurity region in the 1st conductivity type element isolation region. CONSTITUTION:N<+> type buried layers 22 and 23 are formed by diffusing arsenic selectively into the parts of the surface of a P-type silicon substrate 21. Then an element isolation region 24 is formed so as to overlap the N<+> type buried layer 23 by annealing after a boron silicate glass film is used as a diffusion source or after boron ions are implanted. Then an N-type epitaxial layer 25 is formed on the substrate 21. At that time, an autodoping layer 26 is formed in the boundary part between the substrate 21 and the epitaxial layer 25. Then, by diffusing boron from the surface side of the epitaxial layer 25 above the P-type buried element isolation layer 24 are forming a P-type element isolation region 27 and by diffusing boron from the P-type buried element isolation region 24 at the same time, an element isolation region unifying the regions 24 and 27 is formed.
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