Post-CMOS micromachined RF varactor with mutual-isolated large-tuning capacitor and low-voltage actuator

A micromachined tunable capacitor is presented, with the variable capacitor electrically isolated from the electrostatic actuator for flexible circuit application. Fabricated in low-resisitivity silicon wafer with CMOS-compatible processes, the device exhibits a large tuning range of 218% under 4 V driving, as well as a high Q-factor of 115 at 1 GHz and a high self-resonance frequency of 9.5 GHz.