A bulk acoustic wave filter comprises a substrate, an insulating layer disposed on the substrate and having a first cavity and a second cavity formed therein, a first bulk-acoustic-wave-resonance-structure disposed on the first cavity and a second bulk-acoustic-wave-resonance-structure disposed on the second cavity. The first bulk-acoustic-wave-resonance-structure comprises a first bottom electrode disposed on the first cavity, a first top electrode disposed on the first bottom electrode, a first piezoelectric layer portion sandwiched between the first top electrode and the first bottom electrode, and a first frequency tuning structure disposed between the first cavity and the first bottom electrode. The second bulk-acoustic-wave-resonance-structure comprises a second bottom electrode disposed on the second cavity, a second top electrode disposed on the second bottom electrode, a second piezoelectric layer portion sandwiched between the second top electrode and the second bottom electrode.

Provided are a solidly mounted resonator and a method for preparing a solidly mounted resonator. The solidly mounted resonator includes: a piezoelectric structure, wherein the piezoelectric structure includes: an upper electrode layer, a lower electrode layer and a piezoelectric layer. The lower electrode layer disposed corresponding to the piezoelectric structure, and the lower electrode layer includes: a protruding portion protruding downward corresponding to a lower surface of the lower electrode layer; the piezoelectric layer is disposed on an upper surface of the lower electrode layer; the upper electrode layer is disposed on an upper surface of the piezoelectric layer.

Provided are a solidly mounted resonator and a method for preparing a solidly mounted resonator. The solidly mounted resonator includes: a piezoelectric structure, wherein the piezoelectric structure includes: an upper electrode layer, a lower electrode layer and a piezoelectric layer. The lower electrode layer disposed corresponding to the piezoelectric structure, and the lower electrode layer includes: a protruding portion protruding downward corresponding to a lower surface of the lower electrode layer; the piezoelectric layer is disposed on an upper surface of the lower electrode layer; the upper electrode layer is disposed on an upper surface of the piezoelectric layer.

The vibrator element includes a base part, a vibrating arm extending from the base part, and a weight provided to the vibrating arm, wherein the weight includes a thick film part, a thin film part thinner in film thickness than the thick film part, and a connection part which is located between the thick film part and the thin film part to connect the thick film part and the thin film part to each other, and which forms a taper shape gradually decreasing in film thickness in a direction from the thick film part side toward the thin film part.

The vibrator element includes a base part, a vibrating arm extending from the base part, and a weight provided to the vibrating arm, wherein the weight includes a thick film part, a thin film part thinner in film thickness than the thick film part, and a connection part which is located between the thick film part and the thin film part to connect the thick film part and the thin film part to each other, and which forms a taper shape gradually decreasing in film thickness in a direction from the thick film part side toward the thin film part.

A vibration element includes a base and a vibrating arm extending from the base. The vibrating arm includes an arm positioned between the base and a weight. A weight film is disposed on the weight. The weight has a first principal surface and a second principal surface in a front and back relationship with respect to a center plane of the arm. A center of gravity of the weight is located between the first principal surface and the center plane of the arm. A center of gravity of the weight film is located between the second principal surface and the center plane of the arm.

A vibration element includes a base and a vibrating arm extending from the base. The vibrating arm includes an arm positioned between the base and a weight. A weight film is disposed on the weight. The weight has a first principal surface and a second principal surface in a front and back relationship with respect to a center plane of the arm. A center of gravity of the weight is located between the first principal surface and the center plane of the arm. A center of gravity of the weight film is located between the second principal surface and the center plane of the arm.

A film bulk acoustic wave resonator comprising a piezoelectric film having a central region defining a main active domain in which a main acoustic wave is generated during operation, an upper electrode disposed on a top surface of the piezoelectric film, a lower electrode disposed on a lower surface of the piezoelectric film, a dielectric material layer disposed on a lower surface of the lower electrode, and lower recessed frame regions disposed laterally on opposite sides of the central region, the lower recessed frame regions defined by regions of one of the dielectric material or of the lower electrode having a lesser thickness than the thickness of the one of the dielectric material layer or of the lower electrode in the central region.

A film bulk acoustic wave resonator comprising a piezoelectric film having a central region defining a main active domain in which a main acoustic wave is generated during operation, an upper electrode disposed on a top surface of the piezoelectric film, a lower electrode disposed on a lower surface of the piezoelectric film, a dielectric material layer disposed on a lower surface of the lower electrode, and lower recessed frame regions disposed laterally on opposite sides of the central region, the lower recessed frame regions defined by regions of one of the dielectric material or of the lower electrode having a lesser thickness than the thickness of the one of the dielectric material layer or of the lower electrode in the central region.

Aspects of this disclosure relate to a bulk acoustic wave device with a plurality of piezoelectric layers having at least one polarization inversion. The bulk acoustic wave device can include a plurality of stacked piezoelectric layers. The plurality of stacked piezoelectric layers can include a piezoelectric layer formed by atomic layer deposition. The bulk acoustic wave device can excite an overtone mode as a main mode. Related filters, multiplexers, packaged radio frequency modules, radio frequency front ends, wireless communication devices, and methods are disclosed.