| 摘要 |
PROBLEM TO BE SOLVED: To obtain a flash memory which can be micromachined, can be increased in degree of integration, has a superior readout current characteristic, and can write data efficiently. SOLUTION: A split gate type flash memory is constituted in a virtual ground array using impurity diffusion layers 5a and 5d formed on a p-type semiconductor substrate 1 as bit and source lines. In the channel regions below floating gates 9 of the memory, p+ regions 6 containing a p-type impurity at the highest concentration are provided in portions adjacent to the drain-side impurity diffusion layers 5s and 5d, and p- regions 10 are provided in portions (below split gates) not covered with the floating gates.
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