| 摘要 |
PURPOSE:To make it possible to control the thickness of an isolating oxide film freely, by changing an isotropic etching step of a substrate into an anisotropic etching step. CONSTITUTION:On an n-type silicon substrate 1, a thermal oxide film 2, a silicon nitride film 3 and a silicon oxide film 4 are sequentially formed. A part, which is to become an isolating region, is etched, and an opening part 5 is formed. With the nitride film 5 as a mask, thermal oxidation is performed. A thermal oxide film 6 is formed on the side surface and the bottom surface of the opening part. Then a nitride film 7 is formed on the entire surface. The oxide film 6 and the nitride film 7 are made to remain only at the side wall part of the opening part 5 by intense anisotropic etching. A silicon oxide film 8 is formed on the entire surface. The film 8 is removed so that the film 8 is made to remain at only the side wall part. With the oxide films 4 and 8 as masks, anisotropic etching is performed in correspondence with the thickness of an isolating oxide film to be formed next, and an opening part 9 is formed. Isotropic etching is added. With the films 3 and 7 as masks, selective etching is performed, and a structure, in which an element regions 10 and the substrate 1 are isolated and insulated with an oxide film 11 (isolating oxide film), is obtained.
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