| 摘要 |
A nonvolatile semiconductor memory device having a memory cell comprising source/drain diffusion layer in p-well formed to a silicon substrate, a floating gate as a first gate, a control gate (word line) as a second gate, and a third gate, in which the floating gate and the p-well are isolated by a tunnel insulator film, the third gate and the p-well are isolated by a gate insulator film, the floating gate and the third gate are isolated by an insulator film, the floating gate and the word line (control gate) are isolated by a insulator film (ONO film), and the second gate film and the word line (control gate) are isolated by a silicon oxide film, respectively, wherein the thickness of the tunnel insulator film is made larger than the thickness of the gate insulator film. Accordingly, the reliability and access time of the device is improved.
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