Self-aligned lateral field excitation film acoustic resonator with very large electromechanical coupling [FBAR]

This paper describes a self-aligned lateral-field excitation (LFE) film bulk acoustic resonator (FBAR) that exhibits an electromechanical coupling coefficient (K/sub t//sup 2/) of 10% at 4.1 GHz, albeit a relatively low Q of 35. The unique features of this resonator include: (1) improved energy trapping structure that does not require an electrode gap close to a micron; and (2) a simple two-mask self-aligned fabrication process that eliminates misalignment between the piezoelectric ZnO and the metal electrode.