This paper is an extension of the work by Wu and Chen (IEEE UFFC, 49 (1), 142, 2002) in which the COM model and the effective permittivity have been adopted to model the frequency response of a layered SAW filter. Matrix formalism for calculating the effective permittivity of a layered piezoelectric medium with IDT buried inside was given first. Summary of the COM model for uniform IDT was presented. Necessary modifications were made to analyze the frequency response of a two-port 1.48 GHz ZnO/Diamond layered SAW filter. The result was in accordance with the existing experimental data in the literature.