In a method of manufacturing a semiconductor device, a flexible tube connects at least part of a path extending from a reaction chamber to a detoxification device through a vacuum pump. A plurality of electrically conductive pads are arranged in spaced apart relationship relative to each other on the substrate surface. During program or erase operations of the array, the method provides a programming voltage for the selected memory cells of the array, and a half-write voltage to the remaining unselected memory cells to avoid disturbing the unselected memory cells of the array.