| 摘要 |
<p>PURPOSE:To shorten detection and deletion time by repeating deletion pulse application until a memory transistor becomes over deletion and applying high voltage to a word line when the over deletion is detected, and pouring electron to a floating gate with tunnel phenomenon. CONSTITUTION:In the case of detecting the over deletion, the power supply voltage is applied to the sources of the transistors 20, 21, 30, and 31 by a high voltage/power supply voltage changeover circuit 37, and a source line 9 is grounded by a high voltage/ground voltage changeover circuit 10. An AH and a TP become 'L', an EV becomes 'H', word lines 5 and 6 become high voltage, Y gate lines 13 and 14 become 'L'. Therefore, the threshold value becomes high while the electron is poured to the floating gate of all the memory transistors by the tunnel phenomenon, and a memory transistor turns from depression to enhancement. Thus, the nonvolatile semiconductor memory with short deletion time can be obtained.</p> |
