A varactor is described that may be constructed in CMOS and has a high tuning range. In some embodiments, the varactor includes a well, a plurality of gates formed over the well and having a capacitive connection to the well, the gates comprising a first subset of the gates that are adjacent and consecutive and coupled to a positive pole of an excitation oscillation signal, and a second subset of the gates that are adjacent and consecutive and coupled to a negative pole of the excitation oscillation signal, and a plurality of source/drain terminals formed over the well and having an ohmic connection to the well, each coupled to a respective gate to receive a control voltage to control the capacitance of the varactor.