Interdigitated Electrodes (IDEs) based sensor in comb-like electrodes structure is also an attractive candidate in gas sensor and biosensor applications, owing to its simple structural design. The sensitivity can be improved based on geometric parameters of the sensor. Hence, in this paper, we study the physical model of the IDEs-based sensor and concern with its geometrical parameters (gap sizes, number of fingers and width of fingers) based on the finite element simulations using COMSOL Multiphysics. The simulation results were used to show the electrical field that generated by the IDEs and compare to other to find the optimum design. Based on the results, the relationship between the geometric parameters and the IDEs performances are studied. The simulation results show that the higher electric fields are generated with the smaller gap size and smaller width of fingers. Besides that, the results show that the gap size and the width of fingers affect the IDEs performance significantly compared to the number of fingers. The IDE with the design 18 fingers, 0.1 mm gap size between fingers and 0.1 mm width of the finger is the optimum design which generates 30.6 kV/m average of electric field magnitude. © 2018 IEEE.