| 摘要 |
PROBLEM TO BE SOLVED: To suppress leakage current and reverse tunneling failures from occurring by forming trenches in a Si substrate, so as to be adjacent to a conductive film and embedding an oxide film in the trenches to form a trench-structured element isolating film. SOLUTION: Rectangular-strip like element isolating films 32, having an oxide film embedded in trenches formed in a p-type Si substrate 31, are formed to define element regions. A floating gate 34 is disposed independently in each memory cell to enter into between the adjacent element isolating films 32 through a gate oxide film 33A on the Si substrate 31, a selective oxide film 35 on the floating gate 34 is formed through selective oxidation method so as to be thick at the center of the floating gate 34 and form a sharp edge 34A on the top of the floating gate 34. Hence, in the data erasing operation the electric field concentration is apt to occur at the end of the floating gate 34.
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