| 摘要 |
PROBLEM TO BE SOLVED: To prevent increase in junction leakage current in source-drain impurity areas, while efficiently suppressing short channel effect. SOLUTION: Source-drain impurity areas 16 sandwiching a channel forming area are formed on the surface of a semiconductor 10. Gate insulating films 11-13 including a charge accumulating means (floating gate 12) inside and a gate electrode (floating gate 14) are layered in the channel forming area. The concentration of impurities in the source-drain areas 16 in semiconductor layers 10' layered on the sides of the floating gate 14 gradually decreases from the top of the semiconductor layers toward the bottom. Preferably, the source-drain areas 16 are deeper than the floating gate 12 and side insulating films 18 are thicker than a tunnel insulating film 11.
|
