| 摘要 |
PURPOSE:To obtain a dielectric isolation substrate having desirable quality and easy to manufacture, by supplying molten polycrystalline silicon onto an electrically insulating coat film while applying supersonic waves thereto and cooling the polycrystalline silicon to cure the same at a proper time for forming a polycrystalline Si layer having a smooth surface and a thickness as desired. CONSTITUTION:A single crystal Si substrate 2 is electrically insulated with a coat film 3, and molten polycrystalline silicon is flowed down onto the electrically insulating coat film 3 while supersonic waves are applied to the substrate 2. During this process, a turning table 4 is kept stationary and a supersonic oscillator 5 is operated so that supersonic waves are transmitted also to the molten polycrystalline silicon supplied to the electrically insulating coat film 3. The molten poly-crystalline silicon thus vibrated by the supersonic waves is caused to flow sufficiently into recesses formed by the electrically insulating coat film 3 and therefore it can be supplied completely without leaving unfilled parts. Further, the molten polycrystalline silicon layer diffused all over the electrically insulating coat film 3 is allowed to have smooth surface. Then, heating is stopped to cure the polycrystalline silicon. In this manner, a polycrystalline Si layer 6 having a smooth surface 6a can be obtained.
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