System and methods for a hollow-disk radial-contour mode resonator structure. The hollow disk reduces the dynamic mass and stiffness of the structure. Since electromechanical coupling C.sub.x/C.sub.o goes as the reciprocal of mass and stiffness, the hollow disk structure has a considerably stronger electromechanical coupling than a solid one at the same frequency, and thus raises C.sub.x/C.sub.o without excessive gap-scaling. Several embodiments of hollow disk resonators are detailed, including asymmetric and symmetric disk configurations.

A MEMS (microelectromechanical system) resonator assembly (100), comprising a support structure (102), a resonator element (101) suspended to the support structure (102), and an actuator for exciting the resonator element (101) to a resonance mode. The resonator element (101) vibrates at resonance frequency f.sub.0 and comprises at least one bulk acoustic resonator (110a, 110b). The ESR*A*f.sub.0 values of the resonator assembly (100) are in the range from 12 mm.sup.2 MHz to 83 mm.sup.2 MHZ.