| 摘要 |
<p>PURPOSE:To reduce the number of times of detection operation and to read multi-level information by impressing plural required voltages to a gate of a multi-level memory cell storing four values information, etc., detecting whether or not a current flows, and reading out the data. CONSTITUTION:For instance, a floating gate type MOSFET memory cell 61 opens a source line 66 while controlling a voltage supplied to a bit line 65, and when a prescribed voltage pulse is impressed to the control gate 69, a threshold value becomes any one of -1V, 1V, 3V, 5V, and four values of binary 00 to 11 are stored. When 2V is impressed to the gate, and the current flows through the memory cell, 0V is impressed to the gate, and the data 00, 01 are read by whether or not the current flows. When no current flows by impressing 2V, the information 10, 11 are read out similarly by impressing 4V, and the number of times of reading detection operation is reduced, and the multi-level data are read out.</p> |
