| 摘要 |
PROBLEM TO BE SOLVED: To form a flat surface of a semiconductor substrate and a flat groove- type element-isolating part at low cost in an effective process. SOLUTION: A foundation silicon oxide film 2 and a polysilicon film 5 are sequentially formed on a silicon substrate 1. In an anisotropic etching step, an opening is formed in the polysilicon film 5 and the foundation silicon oxide film 2 to form a groove 21 reaching the inside of the semiconductor substrate 1. A silicon oxide film 11 is formed in a HDP-CVD method in a way such that the silicon oxide film 11 is embedded in the groove 21. A resist 41 is formed only on the surface of the silicon oxide film 11 in an element separation region, and the silicon oxide film 11 in an active region is removed with a mask of the resist 41 in a dry etching method. After the resist 41 has been removed, only the polysilicon film 5 is removed in a dry etching method. In addition, the foundation oxide film 2 is removed in a wet etching method with a hydrofluoric acid.
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