The adoption of smart antenna techniques in future wireless systems is expected to have a significant impact on the efficient use of the spectrum and the minimisation of the cost of establishing new wireless networks. RF MEMS devices are the potential candidates to revolutionise RF and microwave system implementation for next generation wireless applications. Despite having excellent performances, there are some drawbacks associated with RF MEMS switches. The main challenges with RF MEMS switches are their high actuation voltage, limited reliability and low power handling capability. This thesis presents novel RF MEMS switches which can overcome these issues. To achieve zero power consumption, we have fabricated latching RF MEMS switches. In addition, we have combined thermal actuation and electrostatic actuation mechanisms to achieve lower actuation voltage. We have also developed a novel contactless RF MEMS switch to increase the reliability of the switch. The switch is free from unavoidable stiction and micro-welding problems in other contact types, which in return guarantees high reliability and long lifetime. The proposed device is based on variable capacitance between signal lines and movable grounded electrodes controlled by electrostatic actuator. The movable grounded electrode has the capability to move bi- directionally, therefore the switch can change among ON, OFF and deep-OFF states. Thus, additional isolation can be achieved in the deep-OFF state. The switch shows excellent RF performances. To increase the power handling capability of switch, we have developed a multi-contact Single Pole Single Throw (SPST). The switch achieves uniform current distribution through each contact, thereby increasing power handling capability. The switch is actuated with separate electrodes to control the current density and direction.