| 摘要 |
PURPOSE:To obtain fine complete isolation structure hardly having pattern conversion difference by forming a deep groove having narrow width, penetrating an N<+> type buried diffusion layer and accelerating an anodic oxidation reaction to the lower section of the base of an element formation region from the bottom of the groove. CONSTITUTION:An N<+> type buried diffusion layer 22, an N<-> type epitaxial layer 23, an oxide film 24 for buffer and an silicon nitride film 25 are shaped onto a P-type silicon substrate 21 in succession. Grooves 27 having narrow width reaching the P-type silicon substrate 21 are formed. The P-type silicon substrate 21 under the bases of the grooves 27 and under the base of the N<+> type buried diffusion layer is changed into a porous silicon layer 28 through anodic oxidation treatment. The porous silicon layer 28 is converted into an oxide film layer 29 through thermal oxidation treatment. The side walls of the grooves 27 are also oxidized simultaneously, and protective oxide films 30 are shaped. A polycrystalline silicon film 31 is deposited to bury the grooves 27. The surfaces of the polycrystalline silicon films 31 in the grooves 27 are turned into thermal oxide films 32. The nitride films 25 and the oxide films 24 for buffer are removed, thus acquiring an element formation region 33 completely isolated by the oxide films.
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