An operating method of a semiconductor device includes repeating an erase loop operable to lower threshold voltages of memory cells in a selected memory block by applying an erase voltage to the selected memory block and performing an erase verification to determine whether the threshold voltages of the memory cells in the selected memory block are less than or equal to a target level, wherein an erase voltage is increased by a voltage difference wherein the voltage difference is increased between successive applications of two or more of the erase loops, and repeating a program loop including applying a program voltage to a selected word line to increase threshold voltages of memory cells electrically coupled to the selected word line and performing a program verification to determine whether the threshold voltages are greater than or equal to a target level, wherein a program voltage is increased by a voltage difference wherein the voltage difference is increased between successive applications of two or more program voltages.