This paper for the first time presents an analytical approach for estimating maximum achievable oscillators' frequency in a specific CMOS process independent of their topology. By employing the Mason function in the first place, it has been proven that ring oscillator with an inductive load can achieve higher oscillation frequencies compared to the other topologies. Then, by applying two-port analysis at the oscillation edge, the oscillation frequency as a function of circuit variables like passive network topology, number of stages, elements of the passive network, gain, and the phase difference between two ports can be achieved. In order to evaluate the maximum oscillation frequency, maximized frequency is applied to the space of variables. This analysis proposes a systematic procedure for designing an oscillator with maximum frequency in desired CMOS process for a known quality factor of passive elements. To examine the feasibility of the proposed technique, this methodology is applied to an optimal oscillator structure. The simulation results confirm that maximum achievable oscillator frequency is 20%-30% higher compared to the oscillator designed with conventional approach. The simulations are performed in the 0.18-μm TSMC technology.