US Patent 7301840 Semiconductor memory device

There provided a semiconductor memory device which ensures writing to all memory cells regardless of fluctuations in properties of the memory cells caused by manufacturing error or the like and can reduce write operation time and power consumption. Write operations for a memory cell 1 and a dummy memory cell 1a are controlled based on a write amplifier control signal WAE. Write operation end timing is determined based on a write completion signal WRST which indicates a storage state of the dummy memory cell 1a. The dummy memory cell 1a and peripheral circuitry are designed so that write time required for the dummy memory cell 1a is more than or equal to a maximum of write time required for the memory cells 1.