| 摘要 |
PURPOSE:To obtain an optimum substrate having the elements of different withstand voltages by a method wherein, in the substrate forming process using a dielectric isolation method, a single crystal island region is epitaxially formed, and single crystal island regions having different depths are provided. CONSTITUTION:An anisotropic etching is selectively performed on the substrate with (100) face by providing an oxide film mask, for example, a V-groove having the necessary depth is formed on the low withstand voltage elements, and after an oxide film 24, for example, has been formed in the V-groove, the substrate surface of the high withstand voltage element forming section (bottom surface is to be widened) is exposed. Then, an Si is epitaxially grown on the whole surface , and after a single crystal layer 29 has been formed on the single crystal and a polycrystalline layer 27 has also been formed on the transition region 28 and the oxide film, an oxide film 29 is formed on a single crystal layer 26. Then, using the film 29 as a mask, a layer 27 and a region 28 are removed, the exposed surface 31 of the single crystal is oxidized, and after a polycrystalline Si has been deposited in the desired thickness, the substrate crystal is ground down to the V-groove. Through these procedures, the optimized depth of the island 35 of the low withstand section and the island 36 of the high withstand section can be formed independently and the V-groove part of the high withstand section can also be narrowed, thereby enabling to miniaturize the device. |
