We present an ohmic series radio-frequency microelectromechanical system (RF MEMS) switch based on a moveable corrugated diaphragm that activates switch contact. Corrugation technology is introduced in the diaphragm for reducing the residual stress in the diaphragm. Moreover, a multilayer metallization system containing ruthenium/gold is proposed as a contact metal to address the reliability of the switch contact. The concept of the corrugated diaphragm, together with a ruthenium/gold contact-metal system, is proven by the characterization of fabricated RF MEMS switches to be an effective way to realize reliable electric contact with significantly reduced pull-in voltage. The durability of the switch contact is increased significantly with the introduction of the multilayer metal, compared to a pure gold contact.