The design of a 2GHz reference frequency oscillator in a 65nm CMOS process using a Bulk Acoustic Wave resonator is presented. The oscillator implements digital frequency control using a switched capacitor bank in parallel to the resonator. The tuning range is up to 4MHz with a minimum step of 1.6kHz. The oscillator core is designed to reach low phase noise (-128dBc/Hz at 100kHz offset) at low power consumption (0.9mW) using a differential topology. It is followed by a low noise divider for output at 500MHz with a phase noise of -140dBc/Hz at 100kHz offset.