A novel and useful millimeter-wave digitally controlled oscillator (DCO) that achieve a tuning range greater than 10% and fine frequency resolution less than 1 MHz. Switched metal capacitors are distributed across a passive resonator for tuning the oscillation frequency. To obtain sub-MHz frequency resolution, tuning step attenuation techniques are used that exploit an inductor and a transformer. A 60-GHz fine-resolution inductor-based DCO (L-DCO) and a 60 GHz transformer-coupled DCO (T-DCO), both fabricated in 90 nm CMOS, are disclosed. The phase noise of both DCOs is lower than −90.5 dBc/Hz at 1 MHz offset across 56 to 62 GHz frequency range. The T-DCO achieves a fine frequency tuning step of 2.5 MHz, whereas the L-DCO tuning step is over one order of magnitude finer at 160 kHz.