| 摘要 |
<p>PROBLEM TO BE SOLVED: To facilitate write control, and to improve disturb/retention characteristics by forming a second (p) well into a second (n) well. SOLUTION: A second (p) well 14 is formed into a second (n) well 15. Consequently, even when negative voltage is applied to a p-type semiconductor substrate 11 by a substrate voltage control circuit at the time of a read operation, the (p) well 14 is not biased simultaneously to a negative value, and no disadvantage such as the decrease of operating speed, the increase of a consumption current, etc., is generated. That is, at least one of word line voltages set at the time of read can be set to negative voltage, and the threshold voltage distribution width of a memory cell transistor MT and a space between data can be set wide. Accordingly, write control is facilitated, and disturb/retention characteristics can be improved.</p> |
