Abstract: The elementary filter of the HBAR type includes two resonators (20, 22) of the HBAR type which are each formed by a transducer (8) and a substrate (12) which are coupled in a suitable manner by electroacoustic waves. The first resonator (20), the second resonator (22) and the coupling element (28) by way of evanescent waves include the same monobloc acoustic substrate (12) which is arranged facing and coupled to the piezoelectric transducer (8) by waves having the same longitudinal or transverse vibration mode through the same reference electrode (10).