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.