| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a NAND flash memory which can suppress the expansion of a distribution width of threshold voltage of a memory cell. <P>SOLUTION: A NAND flash memory includes: a first insulating film; a charge holding layer; a second insulating film; and a control gate and further includes: a NAND string to which a plurality of memory cells which store information according to the electric charge held at the charge holding layer are serially connected, and a control circuit which controls voltage to be applied to the control gate and a semiconductor well. After the write-operation and before performing a verification read-operation verifying whether data are written into the selected memory cell, the control circuit applies a first voltage of a same potential as that of the semiconductor-well or a same polarity as that of the writing voltage to the control gate of the selected memory cell and performs a de-trapping operation to apply a second voltage of a same polarity as that of the writing voltage and larger than the first voltage as an absolute value to the control gate of unselected memory cells not to be written. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
