Aspects of this disclosure relate to acoustic wave filters with bulk acoustic wave resonators configured to excite an overtone mode as a main mode. A bulk acoustic wave resonator of the filter can include a plurality of stacked piezoelectric layers positioned between a pair of electrodes.

Techniques for improving Bulk Acoustic Wave (BAW) resonator structures are disclosed, including filters, oscillators and systems that may include such devices. First and second layers of piezoelectric material may be acoustically coupled with one another to have a piezoelectrically excitable resonance mode. The first layer of piezoelectric material may have a first piezoelectric axis orientation, and the second layer of piezoelectric material may have a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. An acoustic reflector electrode may include a first pair of top metal electrode layers electrically and acoustically coupled with the first and second layer of piezoelectric material to excite the piezoelectrically excitable resonance mode at a resonant frequency of the BAW resonator. The acoustic reflector may include a patterned layer.

Techniques for improving Bulk Acoustic Wave (BAW) mass loading of resonator structures are disclosed, including filters, oscillators and systems that may include such devices. First and second layers of piezoelectric material may be acoustically coupled with one another to have a piezoelectrically excitable resonance mode. The first layer of piezoelectric material may have a first piezoelectric axis orientation, and the second layer of piezoelectric material may have a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. An acoustic reflector electrode may include a first pair of top metal electrode layers electrically and acoustically coupled with the first and second layer of piezoelectric material to excite the piezoelectrically excitable resonance mode at a resonant frequency of the BAW resonator. The acoustic reflector may include a mass load layer to facilitate a preselected frequency compensation in the resonant frequency.

Techniques for improving Bulk Acoustic Wave (BAW) resonator structures are disclosed, including filters, oscillators and systems that may include such devices. A first layer of piezoelectric material having a piezoelectrically excitable resonance mode may be provided. The first layer of piezoelectric material may have a thickness so that the bulk acoustic wave resonator has a resonant frequency. The first layer of piezoelectric material may include a first pair of sublayers of piezoelectric material, and a first layer of temperature compensating material. A substrate may be provided.

Techniques for improving acoustic wave device structures are disclosed, including filters, oscillators and systems that may include such devices. First and second layers of piezoelectric material may be acoustically coupled with one another to have a piezoelectrically excitable resonance mode. The first layer of piezoelectric material may have a first piezoelectric axis orientation, and the second layer of piezoelectric material may have a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. The first and second layers of piezoelectric material have respective thicknesses so that the acoustic wave device has a resonant frequency that is in a super high frequency band or an extremely high frequency band.

Techniques for improving Bulk Acoustic Wave (BAW) resonator structures are disclosed, including filters, oscillators and systems that may include such devices. First and second layers of piezoelectric material may be acoustically coupled with one another to have a piezoelectrically excitable resonance mode. The first layer of piezoelectric material may have a first piezoelectric axis orientation, and the second layer of piezoelectric material may have a second piezoelectric axis orientation that opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. A top acoustic reflector including a first pair of top metal electrode layers may be electrically and acoustically coupled with the first layer of piezoelectric material to excite the piezoelectrically excitable main resonance mode at a resonant frequency.

Techniques for improving Bulk Acoustic Wave (BAW) resonator structures are disclosed, including filters, oscillators and systems that may include such devices. A first layer of doped piezoelectric layer material and a second layer of piezoelectric material may be acoustically coupled with one another to have a piezoelectrically excitable resonance mode. The first layer of doped piezoelectric material may have a first piezoelectric axis orientation, and the second layer of piezoelectric material may have a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. An acoustic reflector including a first pair of metal electrode layers may be electrically and acoustically coupled with the first layer of doped piezoelectric material and the second layer of piezoelectric material to excite the piezoelectrically excitable main resonance mode at a resonant frequency.

Techniques for improving acoustic wave device structures are disclosed, including filters and systems that may include such devices. An acoustic wave device may include a substrate. The acoustic wave device may include first and second layers of piezoelectric material acoustically coupled with one another, in which the first layer of piezoelectric material has a first piezoelectric axis orientation, and the second layer of piezoelectric material has a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. The acoustic wave device may include an interposer layer interposed between the first and second layers of piezoelectric material. The interposer may facilitate an enhancement of an electromechanical coupling coefficient of the acoustic wave device.

Techniques for improving Bulk Acoustic Wave (BAW) reflector and resonator structures are disclosed, including filters, oscillators and systems that may include such devices. First and second layers of piezoelectric material may be acoustically coupled with one another to have a piezoelectrically excitable resonance mode. The first layer of piezoelectric material may have a first piezoelectric axis orientation, and the second layer of piezoelectric material may have a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. A top acoustic reflector electrode may include a first pair of top metal electrode layers electrically and acoustically coupled with the first and second layer of piezoelectric material to excite the piezoelectrically excitable resonance mode at a resonant frequency of the BAW resonator. The resonant frequency of the BAW resonator may be in a super high frequency band or an extremely high frequency band.

Techniques for improving Bulk Acoustic Wave (BAW) resonator structures are disclosed, including fluidic systems, oscillators and systems that may include such devices. A bulk acoustic wave (BAW) resonator may comprise a substrate and a first layer of piezoelectric material. The bulk acoustic wave (BAW) resonator may comprise a top electrode. A sensing region may be acoustically coupled with the top electrode of the bulk acoustic wave (BAW) resonator.