Nonvolatile semiconductor memory device and method of programming in nonvolatile semiconductor memory device

摘要

A memory cell array includes a plurality of memory cells each of which has a control gate and a floating gate. A programming circuit operates in a first programming mode followed by a second programming mode. In the first programming mode, the programming circuit applies a first program pulse to first memory cells while progressively increasing a programming capability of the first program pulse until threshold voltages of the first memory cells become higher than or equal to a first reference voltage. In the second programming mode, the programming circuit applies a second program pulse to second memory cells included in the first memory cells and having threshold voltages lower than a second reference voltage that is higher than the first reference voltage until the threshold voltages of the second memory cells become higher than or equal to the second reference voltage.