| 摘要 |
PURPOSE:To form a high-quality memory which is suitable for such characteristics as the leakage current of an element, dielectric strength of a gate, etc., and can be suitably formed by depressing the surface of a semiconductor in a memory forming area by selective oxidation. CONSTITUTION:A silicon oxide film 2 and silicon nitride film 3 are continuously deposited on the surface of a silicon substrate 1. Then a resist material is left on the surface of the film 3 except a memory array forming part by photolithography and the film 3 is removed from the memory array forming part by dry etching. After removing the film 3, the resist material used for the dry etching as a mask is removed. When the substrate 1 is oxidized thereafter, an oxide film 4 is selectively fornted in the memory array forming part, because the other part of the substrate 1 than the memory array forming part is not oxidized due to the silicon nitride film 3 covering the substrate 1. After forming the oxide film 4, the silicon nitride film 3 and silicon oxide films 2 and 4 are removed by wet etching. Consequently, only the memory array forming part is depressed from the other part. Therefore, a high-quality memory can be formed by using the depressed part. |
