Aspects of the present disclosure provide semiconductor variable capacitor devices. In one embodiment, a semiconductor variable capacitor includes a gate oxide layer comprising a first layer portion with a first thickness and a second layer portion with a second thickness; a first non-insulative region disposed above the gate oxide layer; a first semiconductor region disposed beneath the gate oxide layer; a second semiconductor region disposed beneath the gate oxide layer and adjacent to the first semiconductor region, wherein the second semiconductor region comprises a different doping type than the first semiconductor region a second non-insulative region coupled to the first semiconductor region; and a control terminal coupled to a control region coupled to the second semiconductor region such that a first capacitance between the first non-insulative region and the second non-insulative region is configured to be adjusted by varying a control voltage applied to the control region.