This paper proposes a high frequency resolution Digitally-Controlled Oscillator (DCO) using a single-period control bit switching scheme. The proposed scheme controls the tuning word of DCO in a single period for the fine frequency tuning. The LC type DCO is implemented to realize the proposed scheme, and is fabricated using a standard 65 nm CMOS technology. The measurement results show that the implemented DCO improves the frequency resolution from 560 kHz to 180 kHz without phase noise degradation with an additional area of 200 µm2.