A method of fabricating MEMS device includes forming a plurality of rounded edge trenches on a sacrificial layer over a carrier substrate. Then, formation of a polycrystalline silicon layer over the sacrificial layer to fill the trenches. A plurality of stoppers is defined by the trenches and protrudes from the polycrystalline silicon layer toward the carrier substrate Subsequently, a portion of the sacrificial layer is removed to define a recess between the polycrystalline silicon layer and a carrier substrate and expose the stoppers.