| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a multi-value cell type mask ROM enabling the accurate data read even when the gate voltage/threshold voltage varies, ascribing to the process or circuit. SOLUTION: The semiconductor memory has a plurality of reference cells R-CELL set to different threshold voltages corresponding to those of memory cells as reference voltage generators V-REF for generating reference voltages for reading data in a multi-value cell type mask ROM, corresponding word voltages VG1, VG2, VG3 are fed to the reference cells R-CELL, a voltage is outputted as a reference voltage RA from a reference cell selected among the plurality of reference cells R-CELL. When the threshold voltage or gate voltage of a memory cell M-CELL varies corresponding to which the threshold voltage or gate voltage also varies in the reference voltage generator V-REF and a reference voltage RA corresponding to this variation is generated to enable the accurate read of data from the memory cells.</p> |
