Certain aspects of the present disclosure generally relate to a semiconductor variable capacitor offering at least two types of capacitance tuning, as well as techniques for fabricating the same. For example, a CMOS-compatible silicon on insulator (SOI) process with a buried oxide (BOX) layer may provide a transcap with a front gate (above the BOX layer) and a back gate (beneath the BOX layer). The front gate may offer lower voltage, coarse capacitance tuning, whereas the back gate may offer higher voltage, fine capacitance tuning. By offering both types of capacitance tuning, such transcaps may provide greater capacitance resolution. Several variations of transcaps with front gate and back gate tuning are illustrated and described herein.