| 摘要 |
PROBLEM TO BE SOLVED: To suppress dispersion in a threshold voltage at writing/erasing of a nonvolatile semiconductor device by optimizing both tunnel insulating film characteristics and gate insulating film characteristics, between a floating gate and control gate with a process which is relatively simplified. SOLUTION: A floating gate 14 formed on a semiconductor substrate 11 via a tunnel insulating film 13 and a control gate 16 formed on the floating gate 14 via a gate insulating film 15 are provided. Here, the floating gate 14 is formed of first and second impurity concentration layers 14a and 14b with a phosphorus which is single impurity doped at different concentrations, respectively, while the particle size of the first impurity concentration layer 14a on the side of tunnel insulating film 13 is smaller than that of the second impurity concentration layer 14b.
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