An analysis of an unbounded thin film bulk acoustic wave piezoelectric resonator with a circular driving electrode

We propose using a circular driving electrode on a conventional thin film bulk acoustic wave resonator with a square piezoelectric film on a square ground electrode and a square dielectric layer. The circular driving electrode has the advantage of avoiding the electric field concentration at the corners of a square driving electrode and the related negative effects. A circular driving electrode is also perfectly consistent with the in-plane material isotropy of common thin film resonator materials such as AlN and ZnO. A theoretical analysis on the proposed resonator was performed to obtain the basic vibration characteristics including resonant frequencies and mode shapes.