| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a nonvolatile semiconductor memory device for shortening a writing time and suppressing the increase in reading voltage. <P>SOLUTION: A nonvolatile semiconductor memory device comprises a memory unit and a control unit. The memory unit has a laminated structure, a semiconductor pillar, a storage layer, an inner insulating film, an outer insulating film and a memory cell transistor. The control unit performs control of setting each threshold of the memory cell transistor to either positive or negative and performs control so that the width of distribution of m-th threshold (m is an integer of 1 or more which is smaller than n) having the same sign as the n-th threshold is set narrower than the width of distribution of the n-th threshold which is most distant from 0 volts among the respective thresholds. <P>COPYRIGHT: (C)2012,JPO&INPIT |
