| 摘要 |
PURPOSE:To increase the effective area of an element forming region, by a method wherein, by partially eliminating an element isolation film on an Si substrate and exposing a part of the substrate surface, the film thickness on the side in contact with the element forming region is made small, while the film thickness on the other side is made large. CONSTITUTION:A field isolation oxide film 5a is formed on an Si substrate 1, and the surface region of the substrate 1 surrounded by the oxide film 5a forms each of the element forming regions 6a, 6b. The oxide film 5a has different sectional shapes on the sides in contact with the element forming regions 6a and 6b. On the element forming region 6a side, a part of the field isolation oxide film 5a is eliminated, and the surface region of the substrate 1 is magnified. On the region 6b side, the thickness of the oxide film 5a is formed to be thick, and maintain sufficient isolation breakdown strength. When such an asymmetric field isolation oxide film structure is formed, the effective area is increased in the region where the decrease of the element forming region is wanted to be prevented because of the formation of bird's beak, and insulation isolation is surely enabled. Further a storage device of large capacity can be obtained by using this isolation film. |
