Patent ID: 7221030

Claim:
A semiconductor device, comprising: a plurality of first elements formed in a first region of a semiconductor substrate; a first trench formed between said first elements in said first region; a first silicon oxide film formed on the side and bottom portion of said first trench; a first element-isolating film including an insulting material which fills said first trench; a plurality of second elements which are formed in a second region of said semiconductor substrate and to which a voltage higher than that of said first element is supplied; a second trench formed between said second elements in said second region; a second silicon oxide film formed on the side and bottom portion of said second trench; and a second element-isolating film including an insulating material which fills said second trench, wherein a curvature of a corner of said semiconductor substrate around said second trench is larger than a curvature of a corner of said semiconductor substrate around said first trench; wherein a second oxide film formed in said second elements is thicker than a first oxide film formed in said first element; wherein said second silicon oxide film formed on the side and bottom portion of said second trench is as thick as said first silicon oxide film formed on the side and bottom portion of said first trench; and wherein said second element is a memory cell of a nonvolatile semiconductor memory.