| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve the reliability of a semiconductor memory at a low cost. SOLUTION: A discrimination voltage supplying circuit 2 generates read- voltage under control of a control circuit 1, and supplies it to a memory cell array 7 through a word line Wi decided by address data Address. A discriminating circuit 6 obtains data read out at the time through a Y selector 5 and a sense amplifier 8, and holds it. The decision voltage supplying circuit 2 generates determine-verify voltage between read-voltage and write-verify voltage, and supplies it to the memory cell array 7 in the same way. The decision circuit 6 compares data read out at the time with data previously held. When a storage element of the memory cell array 7 is deteriorated and a threshold value of gate voltage is reduced, data cannot be read out correctly by the determine- verify voltage, the comparison result in the decision circuit 6 is noncoincidence.</p> |
