At the time of an operation of writing data to a specific memory cell in a
memory block, a semiconductor memory device applies a write voltage for a
predetermined period and, after that, performs a verifying operation by
using a sense amplifier circuit and a comparator. When it is found as a
result of the verifying operation that writing to the memory cell is
insufficient, the writing operation is performed again by an instruction
of a memory control circuit. At this time, the memory control circuit
adjusts a write voltage.