In this paper, a tunable parallel plate capacitor with an electrically floating plate has been designed, micromachined and characterized. The device is fabricated from a single metal layer based on a low-cost standard process. The floating tunable capacitor exhibits a higher quality factor (Q-factor) compared to a traditional non-floating capacitor by eliminating the spring's resistive loss in radio frequency (RF) signal path. To minimize the size of the whole device, the tunable capacitor is designed to be actuated using the same parallel plates. Experimental results show that the capacitor has a wide capacitance tuning range of 225% and a high Q-factor of 1150 at 60 MHz. The total size of the device is 1.70 × 1.08 mm2.