AbstractRecently, to meet the demands of multimode/multiband functions for the next generation communication systems, RF MEMS technology is being developed for the reconfigurable transceiver system. In this article, RF MEMS devices such as switches, high‐Q inductors, and high‐Q resonators are reviewed for their operating principles and device structures, as well as the reliability and commercial issues. Single pole single throw (SPST)‐type MEMS switches show characteristics superior to solid‐state switches in the aspects of insertion loss, isolation, and linearity. Single pole multithrow (SPMT) switches will enable ultra small‐sized cellular phones, but insertion loss and coupling between channels should be improved. For a high‐Q inductor, out‐of‐plane inductors show improved results, and an inductor with a Q‐factor of 75 at 1GHz has been fabricated by using the internal stress of a MoCr film. The MEMS inductor improves the performance of a voltage controlled oscillator (VCO), but proper hermetic packaging and standard libraries are also necessary for mass production. The MEMS resonator can operate up to 1.4 GHz and can be used as an oscillator for the timing device as well as component of the filter circuit. The SiTime Company recently has started delivery of a product with performance similar to the quartz oscillator, in which they solved the reliability issues by modifying the annealing and vacuum packaging. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.