The disclosure provides a semiconductor device and an erasing method that may alleviate the deterioration of a memory cell caused by ISPE. The NAND flash memory in the disclosure includes a memory cell array and an erasing component that erases selected blocks of the memory cell array. The erasing component performs a first erasing verification (EV1) and a second erasing verification (EV2) on the selected block. When the first erasing verification (EV1) passes, and the second erasing verification (EV2) fails, an erase pulse with the same erase voltage as the last time is applied, and when the first erasing verification (EV1) fails, an erase pulse with a step voltage higher than the last time is applied.