The RF model of junction varactors based on physical structure was proposed, the procedure of modeling was studied and then the simulation results using the model were compared with the measurement data. The mean error between the measured s-parameters and simulated s-parameters was less than 3.5% for various device geometries. Therefore, the proposed physical model, which is accurate and scalable over a wide range of layout dimensions, can be effectively used to design radio-frequency integrated circuits (RFIC).