A Micro-Electro-Mechanical Systems (MEMS) device includes a substrate, a dielectric supporting layer, a diaphragm, a backplate. The substrate has a substrate opening corresponding to a diaphragm region. The dielectric supporting layer is disposed on the substrate, having a dielectric opening corresponding to the substrate opening to form the diaphragm region. The diaphragm within the dielectric opening is held by the dielectric supporting layer at a periphery. The backplate is disposed on the dielectric supporting layer, having a plurality of venting holes, connecting to the dielectric opening. The backplate includes a conductive layer and a passivation layer covering over the conductive layer at a first side opposite to the diaphragm, wherein a second side of the conductive layer is facing to the diaphragm and not covered by the passivation layer.