| 摘要 |
PROBLEM TO BE SOLVED: To relieve stress caused by a process, and to suppress crystal defects in a silicon device substrate, in a process of forming a trench type isolation region of the silicon device substrate of an SOI wafer. SOLUTION: A polysilicon film 5A is deposited in a trench 8 formed in a silicon device substrate 3 and on an oxide film 4 on the surface of the silicon device substrate 3, and the polysilicon film 5A in the trench 8 and on the silicon device substrate 3 is etched leaving the polysilicon film 5A as it is on the sidewalls of the trench 8 by anisotropic etching. After that, the oxide film 4 on the silicon device substrate 3 is removed, and by thermal oxidation the trench 8 is filled with an insulating film 6A being an oxide of the polysilicon film 5A on the sidewall parts. At the same time, an oxide film is formed too, and a trench type isolation region is completed.
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