The erase voltage applied to a set of non-volatile storage elements being
erased is structured to provide controlled shifts in the threshold
voltage of the storage elements. The erase voltage is applied as a series
of voltage pulses, when necessary, to shift the threshold voltage of
to-be-erased memory cells below a verify level indicative of an erased
condition. To avoid over-erasing the memory cells, the second erase
voltage pulse is decreased, or not increased, in magnitude when compared
to the previously applied voltage pulse. By decreasing or not increasing
the size of the erase voltage, the amount of charge transferred from the
cells by the second pulse is controlled to more accurately position an
erased threshold voltage distribution for the cells near the verify
level. Subsequent erase voltage pulses are increased in magnitude to
provide further erasing when needed.