A radio frequency voltage controlled oscillator (RF VCO) includes a differential oscillator including two field effect transistors (FETs) in which an electric current flows laterally to a substrate and a current source including a bipolar transistor in which the electric current flows in a direction either perpendicular or lateral to the substrate from an emitter to a collector via a base. Therefore, 1/f noise is very small. Resultantly, the RF VCO using the bipolar junction transistor as the current source reduces the 1/f noise generated by the current source of a RF CMOS VCO and, ultimately, the phase noise of the VCO.