A Lamb wave resonator includes a piezoelectric layer, and a first electrode against a first face of the piezoelectric layer. The first electrode includes fingers and a contact arm, with each finger including a first side in contact with the contact arm and two other sides parallel to one another. Portions of the piezoelectric layer are at least partially etched between the two fingers to form a recess. The fingers are spaced apart from one another by a distance W calculated according to the following equation:W=n·valateralf,withn∈Nwhere,valateral is an acoustic propagation speed of Lamb waves,n is an order of a resonance mode of the Lamb waves,f is a resonance frequency of the Lamb wave resonator.