| 摘要 |
PROBLEM TO BE SOLVED: To provide a nonvolatile semiconductor memory device capable of suppressing a deterioration of a gate oxide film without increasing a memory size. SOLUTION: The nonvolatile semiconductor memory device comprises a P-well 210 formed on a main surface of a semiconductor substrate 201, a plurality of memory cells containing n-type source/drain region formed at a predetermined interval on a surface of the P-type well 210 and a floating gate formed corresponding to the source/drain region, and a bottom n-type layer 207 formed under the P-well 210. In this device, a simultaneous erasing operation of the plurality of the memory cells is conducted by implanting electrons from the n-type layer 207 in floating gates via the P-well 210.
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