| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To make a memory cell to be easily multi-valued by narrowing a distribution width of threshold after the write-in of data in a nonvolatile semiconductor memory. <P>SOLUTION: After a first write-in operation, a second write-in operation is carried out by changing a threshold verifying voltage. At this time, since a relation of Verify(b)=Verify(a)-w/2 is in existence between a first threshold verifying voltage Verify(b) and a second threshold verifying voltage Verify(a), where the distribution width of the threshold after the first write-in operation is defined as w, the distribution width of the threshold after the second write-in operation becomes w/2. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
