| 摘要 |
<p>PURPOSE:To provide a NAND cell type EEPROM capable of shortening the time required for a writing of data/write verify readout operation without being accompanied by an increase in a power consumption. CONSTITUTION:An EEPROM is provided with a memory cell array 1, which has a charge storage layer and a control gate and is arranged with nonvolatile memory cells on a semiconductor substrate, a row decoder 5, which is provided at the end part in the direction of a word line of this cell array 1 and drives the control gate, and a verify control circuit, which sets a unit write time in the memory cells in a prescribed range of the array 1 to perform a writing of data and thereafter, reads out the data written in the memory cells and in the case where there is a memory cell which is insufficient in the writing, performs a rewriting in the memory cell. In the EEPROM, at the time of a write varify readout operation, a voltage to be applied to a well formed with a transistor having a conductivity type inverse to that of a transistor of the array 1 is set in a voltage higher than a supply voltage in the row decoder 5 and when the operation of the verify control circuit is changed from the writing operation of data to the write verify readout operation, this voltage is prevented from being reduced.</p> |
