Abstract: A variable gap stop device which can stop the movement of a drive unit, such as a cylinder which moves a chuck on which a semiconductor wafer is secured in a semiconductor processing equipment. The drive unit includes at least one positioning surface. A movable gap stop unit includes at least one stop surface, and in a preferred embodiment may include two or more different stop surfaces each at a different height. A cylinder moves the movable gap stop unit to position at least one of the stop surfaces to be in and out of alignment with the at least one positioning surface of the drive unit. With such a structure and operation, the at least one positioning surface of the drive unit can abut against the variable stop surfaces of the movable gap stop unit. Based on which of the plural stop surfaces the positioning surface of the drive unit abuts against, a height that the drive unit moves the positioning surface can be controlled, e.g.