| 摘要 |
PROBLEM TO BE SOLVED: To provide a nonvolatile semiconductor storage in which an effective area on a floating gate is enlarged and a capacitance between electrodes is increased by forming a rough polysilicon film on the floating gate electrode without increasing the number of fabricating steps. SOLUTION: Each memory cell has a floating gate 105 made of a polysilicon 104 having the rough surface formed on the surface of a p-type silicon substrate 101 via a gate oxide film 103. Because of the roughness, the effective area of the top face of the floating gate is enlarged. A control gate electrode 108 which also serves as a word line is formed via a gate insulating film 107 on the floating gate 105 and a source region 109 and drain regions 110a, 110b are provided on the surface of the p-type silicon substrate 101. The structure of the memory cell, in which the drain regions and the source region can be formed in the polysilicon film pattern in a self aligned manner and a high capacitance ratio adapted to a low power voltage can be obtained, can be derived with a small number of steps.
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