A first electrode and a sacrificial layer are sequentially formed on a substrate, and then first openings for forming supports inside are formed in the first electrode and the sacrificial layer. The supports are formed in the first openings, and then a second electrode is formed on the sacrificial layer and the supports, thus forming a micro electro mechanical system structure. Afterward, an adhesive is used to adhere and fix a protection structure to the substrate for forming a chamber to enclose the micro electro mechanical system structure, and at least one second opening is preserved on sidewalls of the chamber. A release etch process is subsequently employed to remove the sacrificial layer through the second opening in order to form cavities in an optical interference reflection structure. Finally, the second opening is closed to seal the optical interference reflection structure between the substrate and the protection structure.