A voltage controlled oscillator (VCO) CMOS circuit wherein back gate terminals of CMOS transistors are used to vary the parasitic capacitances of the transistors. The back gate terminals receive a signal from a variable voltage source so that oscillation can be controlled by adjusting the variable voltage. The CMOS transistors are connected across an inductor and the transconductance characteristics of the transistors reduce the resistance of the inductor, thereby improving circuit oscillation and providing enhanced stability and capabilities at high operating frequencies.