| 摘要 |
PURPOSE:To obtain a high quality single crystal region having few crystal defects by a method wherein, utilizing the property in which porous silicon is formed along a current path, a thin porous silicon layer of excellent oxidizing efficiency is formed on the part located directly below a large SOI region. CONSTITUTION:A band-like N type region 5, a P type region 6, and an N type region 7 are epitaxially grown on the surface of a P type substrate 1, P type impurities are diffused from directly above the center part of a band-like buried layer 5, and a band-like N type region 7' having a gap between the N type buried layer 5 is formed. Then, an anodic formation process is performed in an aqueous solution of hydrofluoric acid. To be more precise, the main surface part only is made to come in contact with the solution, and said anodic formation process is performed at the room temperature with the current density of 10mA/ cm<2> using a 47% HF solution, for example. The formation of porosity makes progress in lateral direction in the P type region located at the lower part of the N type region formed on the main surface of the substrate, the above is soon united into one, and the point where the formation of prosity is going to proceed to the internal part of the substrate from the aperture part of the buried N type region is considered as the terminal point of the chemical formation. |
