| 摘要 |
PURPOSE:To obtain flat surface by providing a pattern of insulating film consisting of a plurality of impurity concentration layer where the upper most layer has the maximum concentration on an Si substrate, a poly-Si thin film is laminated thereon, it is subjected to heat treatment and the surface is etched. CONSTITUTION:A thermal oxide film 2 is generated on a single crystal Si substrate 1 and the PSG13 of double layer with phosphorus concentration of 4- 8mol% and 8-14mol% is laminated, followed by opening of the window. Next, a poly-Si 14 is deposited in the same level as the poly-Si 14 and it is processed at the temperature of about 1,000 deg.C. Thereby phosphorus P is diffused into the poly-Si 14 on the PSG13 and is not diffused into the window. After phosphorus P is perfectly diffused into the poly-Si 14 on the film 13, the surface is etched by a mixed solution of fluoric acid, nitric acid and acetic acid. When etching is suspended in such a timing where the film 14 where phosphorus is diffused is removed, the poly-Si with addition of phosphorus can be left within the window by the self-alignment and the surface is flat. With such structure, disconnection of wiring can be eliminated and a high integration density device can be obtained. Moreover, the insulated active layer can be formed by annealing the flat and buried poly-Si with laser beam. |
