A method for making micro-electromechanical system devices includes: (a) forming a sacrificial layer on a device wafer; (b) forming a plurality of loop-shaped through-holes in the sacrificial layer so as to form the sacrificial layer into a plurality of enclosed portions; (c) forming a plurality of cover caps on the sacrificial layer such that the cover caps respectively enclose the enclosed portions of the sacrificial layer; (d) forming a device through-hole in each of active units of the device wafer so as to form an active part suspended in each of the active units; and (e) removing the enclosed portions of the sacrificial layer through the device through-holes in the active units of the device wafer.