This article introduces the reader to the performance limitations of micro electro mechanical gap-tuning capacitors fabricated in the commercially PolyMUMPs (Polysilicon Multi-user MEMS Process) foundry. And the advantages of the CMOS technology to fabrication of MEMS tunable capacitors are discussed. Also to increase the both of tuning range and quality factor, a three-plate MEMS tunable capacitor with two movable plates is designed and simulated. The simulation of the capacitor was done using the EM3DS software which is demonstrated wide tuning range (300 percent), that is 6 times higher than tuning range of the conventional parallel plate capacitor. The proposed capacitor are designed by using the ALCU metal layers of TSMC 0.18 μm CMOS technology that have caused decreasing the series resistance and increasing  the quality factor to 300 in 1 GHZ. Manuscript profile