Nonvolatile semiconductor memory device having a plurality of blocks provided on a plurality of electrically isolated wells

A nonvolatile semiconductor memory device comprising:

• a plurality of blocks each including a plurality of stacked gate memory cells;
• and
• block selection means for selecting one said block in accordance with a block selection address,
• said plurality of blocks being formed in a plurality of first conductivity type wells being electrically isolated from each other,
• said nonvolatile semiconductor memory device further comprising:
• well selection means responsive to an operation mode for supplying a voltage to one said well being provided with said block being selected by said block selection means;
• and
• source selection means responsive to an operation mode for supplying a voltage to sources of said memory cells included in said block being selected by said block selection means.