| 摘要 |
A flash memory includes a semiconductor substrate having a first conductivity type; a first well having a second conductivity type opposite to the first conductivity type, and so formed on the surface of the semiconductor substrate as to be contained in the semiconductor substrate; a second well having the first conductivity type and so formed on the surface of the first well as to be contained in the first well; a plurality of memory cells formed in the second well, each having a floating gate; and an erase portion for erasing charge stored in the memory cells by dissipating it into the channel region of the second well through a tunnel insulating film. The erase portion applies a first erase signal to the first well in response to a start signal instructing the start of erase, applies a second erase signal having the same polarity as that of the first erase signal to the second well, and the first erase signal is applied earlier than the second erase signal. |
