| 摘要 |
A multi-value memory that has an improved data maintain period has been disclosed and, in a multi-value nonvolatile semiconductor memory device comprising a multi-value memory cell having a floating-gate and able to store at least three values, the threshold values of the multi-value memory cell are set from a state in which the threshold values designate at least two boundary values that identify at least three values to a state in which a fixed quantity of charges are injected into the floating gate in a data write operation, the read data is determined from the relationship between the threshold values of the multi-value memory cell and the (at least) two boundary values, and increments (margins) A1, A2 and A3 in the threshold value from threshold values VT1, VT2 and VT3, which are the lower limits of ranges, due to the injection of charges into the floating gate in the data write operation are set so that the increment is larger for data corresponding to a state in which a larger quantity of charges are injected.
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