A micro-electro-mechanical system (MEMS), methods of forming the MEMS and design structures are provided. The method comprises forming a coplanar waveguide (CPW) comprising a signal electrode and a pair of electrodes on a substrate. The method comprises forming a first sacrificial material over the CPW, and a wiring layer over the first sacrificial material and above the CPW. The method comprises forming a second sacrificial material layer over the wiring layer, and forming insulator material about the first sacrificial material and the second sacrificial material. The method comprises forming at least one vent hole in the insulator material to expose portions of the second sacrificial material, and removing the first and second sacrificial material through the vent hole to form a cavity structure about the wiring layer and which exposes the signal line and pair of electrodes below the wiring layer. The vent hole is sealed with sealing material.