Piezoelectric resonator and electronic component provided therewith

1. A piezoelectric resonator for obtaining a signal of a predetermined resonance frequency from a bulk acoustic wave propagating inside a piezoelectric film, the piezoelectric resonator comprising:

a plurality of transducers, each transducer having a first electrode film, a second electrode film, and the piezoelectric film disposed between the first electrode film and the second electrode film,

wherein the plurality of transducers are stacked in a predetermined direction, and

wherein a propagation area of the bulk acoustic wave varies in a propagation direction of the bulk acoustic wave; and

a propagation layer disposed between two transducers out of the plurality of transducers,

wherein an area of the propagation layer is different from an area of at least one transducer out of the plurality of transducers.

2. A piezoelectric resonator for obtaining a signal of a predetermined resonance frequency from a bulk acoustic wave propagating inside a piezoelectric film, the piezoelectric resonator comprising:

a plurality of transducers, each transducer having a first electrode film, a second electrode film, and the piezoelectric film disposed between the first electrode film and the second electrode film,

wherein the plurality of transducers are stacked in a predetermined direction, and

wherein a propagation area of the bulk acoustic wave varies in a propagation direction of the bulk acoustic wave; and

a propagation layer disposed between two transducers out of the plurality of transducers,

wherein an area of the propagation layer is different from an area of at least one transducer out of the plurality of transducers, and

wherein the area of the propagation layer is smaller than the area of at least one transducer out of the plurality of transducers.

3. A piezoelectric resonator for obtaining a signal of a predetermined resonance frequency from a bulk acoustic wave propagating inside a piezoelectric film, the piezoelectric resonator comprising:

a plurality of transducers, each transducer having a first electrode film, a second electrode film, and the piezoelectric film disposed between the first electrode film and the second electrode film,

wherein the plurality of transducers are stacked in a predetermined direction, and

wherein a propagation area of the bulk acoustic wave varies in a propagation direction of the bulk acoustic wave;

a propagation layer disposed between two transducers out of the plurality of transducers,

wherein an area of the propagation layer is different from an area of at least one transducer out of the plurality of transducers, and

wherein the area of the propagation layer is smaller than the area of at least one transducer out of the plurality of transducers; and

an acoustic multilayer reflecting film for reflecting the bulk acoustic wave, the acoustic multilayer reflecting film having a configuration wherein first reflecting films with a predetermined acoustic impedance and second reflecting films with an acoustic impedance different from that of the first reflecting films are alternately stacked in the predetermined direction,

wherein the plurality of transducers are formed on the acoustic multilayer reflecting film, and

wherein the area of the propagation layer is equal to an area of the transducers other than the transducer in contact with the acoustic multilayer reflecting film out of the plurality of transducers.