| 摘要 |
PROBLEM TO BE SOLVED: To make a substrate flat by polishing a single-crystalline silicon layer on an insulation film to a first predetermined thickness and dry-etching it to a second predetermined thickness and then polishing it until the insulation film is exposed. SOLUTION: A single-crystalline silicon layer 32 is ground to a thickness of 3-5μm±0.5μm, for example and then is etched by dry etching to a thickness of 0.5-1.0μm. Next, the whole surface of the single crystal silicon layer 32 is polished at the same time by a selective polishing method with the use of an insulation film 34 as a stopper, until the convex insulation film 34 is exposed and polishing is stopped, when the single crystal silicon layer 32 is polished to the top surface of the insulation film 34. A thin film SOI(silicon-on-insulator) structure having the single-crystalline silicon layer 32 formed into island shape on the insulation film 34 is formed in this manner. Since the amount of polishing is extremely small, unevenness in polishing and hence polishing variation are hardly produced and even if the unevenness in polishing is produced, the polishing variation is small and hence the substrate can be plavarized.
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