| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a semiconductor memory device capable of increasing the writing speed of data by achieving a high speed for a verifying operation. <P>SOLUTION: A memory cell array is constructed by arranging a plurality of memory cells connected to word and bit lines to store n values (n is a natural number of 3 or more) in a matrix. A control circuit controls the potentials of the word and bit lines according to input data to write data in the memory cells. The control circuit performs a writing operation to write at the threshold voltage of a k value (k<=n), precharges the bit line, and then changes the potential of the word line by i times to verify whether the memory cells reach the threshold voltage of an i value (i<=k). Thus, the problem of the long time of the verifying operation is solved. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
