Trapped thickness-extensional modes in high overtone thin film bulk acoustic wave piezoelectric resonators

Abstract

Abstract We perform a theoretical analysis on thin film bulk acoustic wave piezoelectric resonators operating with high overtone thickness-extensional modes. The scalar differential equations by Tiersten and Stevens are used for the electroded and unelectroded parts of the resonator, respectively. An analytical solution is obtained for the free vibration of the resonator. Frequencies and modes are calculated based on the solution. Numerical results show that there exist modes with vibration mainly trapped under the driving electrode. The effects of the structural parameters on the behaviors of the trapping are examined.