| 摘要 |
PROBLEM TO BE SOLVED: To obtain a nonvolatile semiconductor memory device which can be integrated highly in a simple and short production process by a method wherein the whole face of a memory transistor region is provided with a first heavily-doped impurity diffusion layer of a first conductivity type and the surface of a semiconductor substrate in a split gate region is provided with a second lightly-doped impurity diffusion region of the first conductivity type. SOLUTION: N-type impurities are ion-implanted obliquely in a self-alignment process in which a floating gate 204 is maked in a self-aligned manner, and an N<+> diffusion layer 205 is formed. Then, N-type impurities are ion-implanted perpendicularly in a self-alignment process in which the floating gate 204 is used as a self-aligned mask, a P<-> diffusion layer 206 whose concentration is lower than that of a P<+> diffusion layer 202 is formed on a substrate in a split gate region. Thereby, a process can be made simple and short. In addition, the controllability of the split gate region can be enhanced much more. In addition, the threshold voltage of the split gate region can be controlled to a proper value.
|
