Compound solid state switches such as GaAs MESFETs and PIN diodes are widely used in microwave and millimeter wave integrated circuits (MMICs) for telecommunications applications including signal routing, impedance matching networks, and adjustable gain amplifiers. However, these solid-state switches have a large insertion loss (typically 1 dB) in the on state and poor electrical isolation in the off state. The recent developments of micro-electro-mechanical systems (MEMS) have been continuously providing new and improved paradigms in the field of microwave applications. Different configured micromachined miniature switches have been reported. Among these switches, capacitive membrane microwave switching devices present lower insertion loss, higher isolation, better nonlinearity and zero static power consumption.