| 摘要 |
PROBLEM TO BE SOLVED: To form an insulating film over a wafer so as to have a precise thickness at the bottom of a trench, without using inclined ion implantation or a photoresist as an etching mask.SOLUTION: A first insulating film is formed on a semiconductor layer and the inner wall of the trench formed on the semiconductor layer, and then a second insulating film is formed on the first insulating film by CVD so as to fill the inside of the trench, the second insulating film having a smaller etching rate to a first etchant than the first insulating film. The second insulating film is left but is removed on the semiconductor layer. The first insulating film is removed to a predetermined depth from the surface of the semiconductor layer. The upper inner wall of the trench is exposed to remove the second insulating film in the trench by etching with a second etchant having a higher etching rate to the second insulating film than to the first insulating film. The first insulting film is left at the bottom of the trench and then a gate electrode is embedded in the trench. |
