| 摘要 |
PROBLEM TO BE SOLVED: To provide a nonvolatile semiconductor memory capable of improving charge holding characteristics without damaging the characteristics of the injection and extraction of electric charges. SOLUTION: An element isolation region 2 is formed on the surface of a semiconductor substrate 1 and N+ diffusion layers 7 are formed adjacently to the element isolation region 2 with an appropriate interval in an area sectioned by the element isolation region 2. A part between the N+ diffusion layers 7 is turned to a channel area and a tunnel oxidized film 3 is formed between the N+ diffusion layers 7 on the semiconductor substrate 1. A floating gate 4, an inter-gate insulation film 5 and a control gate 6 are successively laminated on the tunnel oxidized film 3, and a gate 10 is composed of the tunnel oxidized film 3, the floating gate 4, the inter-gate insulation film 5 and the control gate 6. For the tunnel oxidized film 3, the projection part 3b of a large film thickness is formed at a center and the thin parts 3a of small film thickness are formed at both ends. Data are written and erased at the thin parts 3a of the small film thickness on both sides.
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