I Introduction
Piezoelectric thin film resonators are widely applied in RF frequency filters and duplexers [1], where one design is the so-called solidly mounted resonator (SMR), as shown in Fig. 1. Here acoustic isolation of the vibrating thin film membrane (upper electrode-piezoelectric-lower electrode) from the substrate is achieved by an acoustic mirror. A common platform for designing SMR devices is the one-dimensional (1-D) Mason's model [2], which allows characterizing the thickness-extensional (TE) resonance and the transmission coefficient for the TE wave at the interface between the piezoelectric layer and the bottom electrode.
Schematic of a leaky plate mode propagating in an SMR structure.