This paper describes an analysis of the close to carrier phase-noise characteristics of the narrow-band Colpitts oscillators. The open-loop impedance, that is, series of the SC-cut resonator and the oscillator active circuit, is calculated using a linear circuit model with a non-linear transistor model. It is shown that the loaded Q can be improved by introducing the resonator filter in the oscillation circuit. Based on the Leeson's model, the near carrier phase-noise is estimated using the calculated Q values. The results corresponded well with the previous experiments. It is also shown that the phase-noise can be exceedingly improved, that is, under -148 dBc/Hz at 10Hz offset, by using resonator filter with high Q.