The tremendously fast expansion of wireless and satellite communication systems in the information age is without parallel in history, leading to increase in the demand for miniaturized communication systems with smaller sizes, lighter weights, better functionalities and higher reliabilities. RF MEMS are widely recognized as enabling technologies for the miniaturization due to their promising characteristics of broadband operation, low power consumption and insertion loss, high isolation, and excellent signal linearity. In the past decade, RF MEMS switches are receiving much more attention for communication systems including tuneable matching networks, phase shifters, resonators, and reconfigurable filters. Nevertheless, challenges remain for the RF switches, restricting their applications in many systems. Reliability, packaging, switching speed, and power handling are among the common challenges shared by MEMS switches. This thesis presents a novel wafer-level encapsulated RF MEMS switch based on a multimetal contact containing ruthenium and a corrugated Si02/Si3N 4 diaphragm. A concept of stacked wafers is proposed to achieve near-hermetic and encapsulated switches, where wafers are processed separately and are subsequently bonded by wafer bonding. A novel multi-layer metal-contact concept, comprising a Cr/Ru/Au/Ru structure, is introduced to improve the contact reliability by having a hard-metal surface of ruthenium without substantial compromise in the contact resistances. The novel contact metallization scheme is proven to be an effective method to increase the contact durability. At a measurement xii