| 摘要 |
PROBLEM TO BE SOLVED: To provide an SOI substrate forming method that easily achieves thinning of a semiconductor layer and that of a buried oxide film, and a method for manufacturing a nonvolatile semiconductor storage device of a NAND type or the like that uses the SOI substrate formed by the SOI substrate forming method. SOLUTION: The SOI substrate forming method includes a step for forming an intermediate layer which is etched at an etching speed larger than that of a substrate 1, and composed of a material that allows selection of an intermediate-layer etchant, on the substrate 1 composed of a semiconductor including silicon; a step for forming the semiconductor layer 3 which is composed of a material that is etched at an etching speed smaller than that of the intermediate layer by the intermediate-layer etchant, on the intermediate layer; a step for forming an air gap between the substrate 1 and the semiconductor layer 3 by selectively etching the intermediate layer with respect to the substrate 1 and the semiconductor layer 3, while using the intermediate-layer etchant; and a step for burying the buried oxide films 4x, 4y between the substrate 1 and the semiconductor layer 3, by thermally oxidizing the substrate 1 and semiconductor layer 3 on the air-gap side. COPYRIGHT: (C)2008,JPO&INPIT
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