To provide a semiconductor memory device comprising a phase-change memory
and having high compatibility with DRAM interface. The memory cell array
18 comprises a memory cell that includes a phase-change element provided
at the intersection of a bit line and word line. A write address and data
accompanying a write request are temporarily held in a write address
register 15 and a data register 14 respectively, and a write operation is
not performed on the memory cell array 18 in this cycle of write request.
And when a next write request occurs, the held data is written to the
memory cell array 18. At this time, two write cycles--RESET cycle and SET
cycle--are provided. Then the written contents of the memory cell and the
rewrite data are compared, and after only SET cells are temporarily RESET
(amorphization, increasing the resistance), it is operated so as to write
only SET data (crystallization, lowering the resistance).