In this work, a thin-film packaging was developed to be used for radio-frequency microelectromechanical system configurations. The fabricated packages are suspended membranes in the multilayer SixNy/aSi/SixNy on conductive coplanar waveguides (CPWs) of different length. Several geometric parameters of the membranes, which are the length, the curvature radius at the vertices of the rectangular base, the density and the diameter of holes on the capping surface, were also varied. The mechanical properties of the suspended membranes were investigated by mechanical simulations and surface profilometry measurements as a function of the geometric parameters. RF characterization was performed to evaluate the impact of the package on the CPW performance. Finally, network analysis was carried out, allowing to clarify the origin of the RF losses measured for the fabricated microdevices.