| 摘要 |
PURPOSE:To obtain the active element having both excellent high frequency characteristics and high breakdown strength by a method wherein a single crystal is grown and oxidized on a polycrystalline layer or an amorphous layer, and the single crystal is electrically isolated from a semiconductor substrate. CONSTITUTION:A thick thermally oxided film 31 is formed on a silicon substrate, and then a patterning is performed on an active element region 21. Subsequently, a polycrystalline silicon film 71 is formed on all over the surface, and boron is diffused on the polycrystalline silicon film so that the silicon film will be susceptible for oxidization when it is oxidized later. Then, a photoresist is thickly coated, and after it has been flattened, dry etching is performed on the whole surface until the thermally oxidized film 31 is exposed, and the photoresist is removed. Subsequently, when an epitaxial growing method is selectively performed at the temperature of 950 deg.C or thereabout, single crystal silicon 61 is grown on the polycrystalline silicon 71 only, and the polycrystalline silicon is turned into an oxide film 51 when a thermal oxidization is performed. Then, when etching is conducted as thick as the oxide film 81 on the single crystal silicon 61, the single crystal can be isolated completely by the oxide film.
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