The passive devices used in the wireless communication system ¡]including resistor, capacitor and inductor¡^usually need high quality factor and low power dissipation characteristics. This thesis aims to develop a micro tunable capacitor with high-quality-factor and wide-tuning-range using surface micromachining. In contrast with conventional low-tuning-rate parallel-plate tunable capacitors, this research presents a concave structure and eight-suspending-beams layout design of the top electrode to enhance the elastic rigidity and tuning rate. In addition, this study appropriately decreases the thickness of top electrode, the tuning rate of such device can be improved to 65~2100%. On the other hand, in order to substantially increase quality factor, this thesis adopted the glass substrate ¡]Corning 7740¡^to reduce the power dissipation of high frequency operating signal. The optimized quality factor of this work is approximately equal to 41 under 2.4 GHz operation frequency. The material of sacrificial layer and top electrode adopted in this dissertation is aluminum and gold respectively. To avoid any breakage of the vertical supporting beams during releasing process, this research appropriately increases the width of vertical supporting beams, however, keep the thickness of the suspending part of top electrode for the maintenance of high quality factor and low driving voltage.