A digitally controlled oscillator provides high resolution in frequency tuning by using a digitally controlled capacitive network that includes a tunable capacitive circuit, a first capacitor and a second capacitor. The tunable capacitive circuit generates a variable capacitance according to a digital control word. The first capacitor is coupled in an electrically parallel configuration with the tunable capacitive circuit. The second capacitor is coupled in an electrically serial configuration with a combination of the first capacitor and the tunable capacitive circuit. The first capacitor and the second capacitor are sized such that an effective capacitance of the digitally controlled capacitor network has a step size that is a fraction of a step size of the variable capacitance in response to an incremental change in the digital control word.