| 摘要 |
PURPOSE:To increase breakdown strength of the trench type capacitor of a dynamic RAM, by forming, on a single crystal silicon wafer, a trench wherein the face orientation of the bottom surface and the side surface of the trench is (100) and that of a part where surfaces are in contact is not (100), and forming, after that, a thermal oxidation film. CONSTITUTION:A P-type Si substrate 2 is subjected to etching applying an SiO2 film 12 to a mask, and a trench is formed. In this process, the etching is so performed that a part where the surfaces of the trench are in contact becomes a face other than (100). This can be easily done by an isotropic etching (RIE). Then As is diffused into the bottom surface and the side surface of the trench, and an N<+> layer 3 is formed. After the film 12 is eliminated, an SiO film 1 is formed by a thermal oxidation under the condition where the rate of oxidation depends largely on the face orientation. A polysilicon film 6 in which phosphorus is doped is formed on the SiO film 1. Thereby, the oxide film of a part where surfaces are in contact is made thicker than the bottom surface and the side surface, and so breakdown strength is improved. |
