Surface acoustic wave (SAW) resonators are widely used for frequency selection in mobile and wireless transmission systems [1]. SAW devices consist of a piezoelectric substrate, interdigital transducers (IDTs), and reflectors deposited on top of the substrate [2]. When voltage is applied to the electrodes, it generates electric fields, which produce piezoelectric voltages that propagate in both directions, as shown in Fig. 1(b). Therefore, surface acoustic waves are generated through the inverse piezoelectric effect [3]. The fundamental resonant frequency is determined by the acoustic wave speed and wavelength as shown in (1). Therefore, the design of the IDT is critical to determine the GHz resonance frequency as shown in Fig. 1. Discrete SAW resonators suffer from leaky interface and consume large area [4]. In this work, the SAW resonator was developed ZnO piezoelectric material on silicon [2] to enable the integration of the SAW resonator with integrated circuits. The resonator IDTs were formed using metal layers found in the standard 0.35 μm CMOS process to make a 1 GHz resonator. The important parameters affecting the performance of the SAW resonator are the electromechanical coupling coefficient, k2, high factor quality, Q and low insertion loss. This paper studies the effect of different piezoelectric thickness of ZnO and different distance of input and output transducer, Lc, on the electromechanical coupling coefficient of SAW resonator. Finite element simulations of the ZnO SAW resonator were conducted using COMSOLTM. A 2D geometry of the SAW resonator was drawn under the piezoelectric model. Two analyzes were applied: eigenfrequency analysis, frequency domain analysis. Harmonic excitation as a sine wave has been applied to...... center of the paper...... ounce frequencies are trapped inside the cavity to ensure maximum reflection when the IDT is placed on a integer equal to half the wavelength. By varying the thickness of the piezoelectric thin film, the phase velocity of the acoustic wave will also be varied. Fig. 5 shows the SAW velocity dispersion of the surface acoustic wave resonator for the normalized thickness of the ZnO piezoelectric material. There is a slight decrease in phase velocity with normalized ZnO thickness between 0.35 and 0.95. The phase velocity increases with increasing thickness of ZnO in a range between 3150 m/s and 3650 m/s. The result shows that the effective normalized thickness of the ZnO piezoelectric layer between 0.63<(hzno/λ)<0.78 and the closest distance of the input and output transducer (Lc =1.6 um) gives the coefficient of Higher electromechanical coupling to improve CMOS SAW resonator performance.