| 摘要 |
<p>PURPOSE:To provide a NAND cell type EEPROM in which a block can be erased at a high speed. CONSTITUTION:The nonvolatile semiconductor memory comprises a memory cell array in which memory cells having p-type wells formed on an n-type substrate and each having a floating gate and a control gate are arranged in a matrix in such a manner to be electrically rewritable by communicating charge between the floating gate and the well and that a plurality of the cells are connected in series to form a NAND cell to connect a bit line through a selective gate. The memory also comprises data erasing means for applying a ground potential to all control gates in selected plurality of NAND cell blocks 201, 202 and an erasing potential to all control gates in non-selected blocks 203-20n, all selected gates in all the blocks 201-20n and the wells, and means for varying the number of the NAND cell blocks to be selectively erased.</p> |
