Nonvolatile semiconductor memory and method of controlling the nonvolatile semiconductor memory

A nonvolatile semiconductor memory comprising:

• a memory cell array, the memory cell array including a memory string and a matrix of a plurality of memory cell units, the memory string containing a plurality of memory cells that are provided on the substrate, store data according to a threshold voltage, allow electrical writing and erasure of data, and are connected in series, the memory cell unit containing a first selecting gate transistor that connects a first end of the memory string to a bit line and a second selecting gate transistor that connects a second end of the memory string to a source line;
• and
• a driver that controls a voltage of a substrate,
• wherein after data is written in selected one of the memory cells, the voltage of the substrate is controlled for a specified period to be higher than a voltage of a word line connected to the selected memory cell.