| 摘要 |
PROBLEM TO BE SOLVED: To realize a writing method in which fluctuation in the threshold value of memory cell can be suppressed in a virtually grounded array. SOLUTION: In a method for writing a data into a virtually grounded array having a plurality of word lines WL connected with the control gate of a memory cell having a floating gate where three types or more of data can be written and erased electrically, and a plurality of bit lines connected with the drain and source thereof while being shared between adjacent rows, a write drain voltage is set (S2) after a program is set up (S1) and then the data is verified (S3). The voltage being applied to WL is set higher than a threshold level (first threshold level) being arranged finally. The voltage is arranged to the first threshold level by repeating the steps S2, S3 (first write step). Upon finishing the operation for all memory cells to be written, the verify step (S4) and the write step (D5) are repeated (second write step) while varying the voltage of WL until the final threshold level to be arranged is reached.
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