| 摘要 |
PROBLEM TO BE SOLVED: To increase the charge injecting efficiency at writing time without causing the deterioration of durability caused by the deterioration of a tunnel oxide film by setting the lengths of the edge sections of a floating gate and an impurity area which adjoin each other through an oxide film. SOLUTION: Each edge section 20 of impurity areas 13 and both edge sections 21 of a floating gate 16 and a control gate 18 draw an arc having a chord equal to a gate width W perpendicularly to the direction of a gate length L2 along the direction of the distance between both impurity areas. The gate width W is roughly coincident with the widths of the impurity areas 13. Therefore, the size L1 of each edge section 20 of the impurity areas 13 and both edge sections 21 of the floating and control gates 16 and 18 shows a larger value than the width W. Consequently, the injection of charges into the floating gate 16 or discharge of the charges from the gate 16 can be performed efficiently and the writing speed of information in a nonvolatile semiconductor storage device can be increased.
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