Elastic effects of electrode on thin film bulk acoustic resonator (FBAR)

The elastic effects of the electrode on the effective electromechanical coupling factor, keff², and the resonance factor, Qs, of thin-film bulk acoustic resonators (FBAR) are investigated by numerical simulation. Results indicate that the acoustic impedance ratio of the electrode to the piezo-film dominantly determines the behaviors of the keff², the variation of Qs versus the thickness of the electrode crucially depends on the acoustic impedance ratio of electrode to piezoelectric films. The results will be applied in the theoretical optimization of FBAR, which are available to improve the fabrications of FBARs and similar devices.