Acoustic resonators and filter devices. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having front and back surfaces. The back surface is attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm spanning a cavity in the substrate. A conductor pattern formed is formed on the front surface of the piezoelectric plate, including an interdigital transducer (IDT) with interleaved fingers of the IDT on the diaphragm. The substrate and the piezoelectric plate are the same material.

An acoustic wave device includes a support substrate, a piezoelectric layer, and a functional electrode. As seen in a first direction of the support substrate, the piezoelectric layer overlaps the support substrate. The functional electrode extends over a first major surface of the piezoelectric layer. A space is opposite to the first major surface of the piezoelectric layer and at or adjacent to a second major surface of the piezoelectric layer. In the first direction, the functional electrode extends over an overlap region that overlaps the space, and a non-overlap region that does not overlap the space. In the non-overlap region, at least one of an insulating film and a void is located between the functional electrode and the piezoelectric layer.

A resonator circuit device. The present invention provides for improved resonator shapes using egg-shaped, partial egg-shaped, and asymmetrical partial egg-shaped resonator structures. These resonator shapes are configured to give less spurious mode/noise below the resonant frequency (F.sub.s) than rectangular, circular, and elliptical resonator shapes. These improved resonator shapes also provide filter layout flexibility, which allows for more compact resonator devices compared to resonator devices using conventionally shaped resonators.

A BAW resonance device comprises a first layer including a cavity located on a first side, a first electrode having a first end located in the cavity and a second end contacting with the first layer, a second layer located on the first side, and a second electrode located on the second layer above the cavity, wherein the first electrode and the second electrode are located on two sides of the second layer. The first electrode comprises a first electrode layer and a second electrode layer, and the second electrode layer and the second layer are located on two sides of the first electrode layer. The second electrode comprises a third electrode layer and a fourth electrode layer, and the second layer and the fourth electrode layer are located on two sides of the third electrode layer. Thus, the electrical resistance is lowered and the electrical losses are reduced.

Filter devices are disclosed. A filter device includes a piezoelectric plate comprising a supported portion, a first diaphragm, and a second diaphragm. The supported portion is attached to a substrate and the first and second diaphragms spans respective cavities in the substrate. A first interdigital transducer (IDT) has interleaved fingers on the first diaphragm. A second interdigital transducer (IDT) has interleaved fingers on the second diaphragm. A first dielectric layer is between the interleaved fingers of the first IDT, and a second dielectric layer is between the interleaved fingers of the second IDT. A thickness of the first dielectric layer is greater than a thickness of the second dielectric layer. The piezoelectric plate and the first and second IDTs are configured such that radio frequency signals applied to first and second IDTs excite primary shear acoustic modes in the respective diaphragms.

Piston mode Lamb wave resonators are disclosed. A piston mode Lamb wave resonator can include a piezoelectric layer, such as an aluminum nitride layer, and an interdigital transducer on the piezoelectric layer. The piston mode Lamb wave resonator has an active region and a border region, in which the border region has a velocity with a lower magnitude than a velocity of the active region. The border region can suppress a transverse mode.

Methods of fabricating resonator and filter devices. A first conductor pattern formed on a front surface of a piezoelectric plate includes a first plurality of contact pads and an interdigital transducer (IDT). The IDT and the piezoelectric plate are configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the piezoelectric plate. An acoustic Bragg reflector is between a substrate and a back surface of the piezoelectric plate, the acoustic Bragg reflector configured to reflect the shear primary acoustic mode. A second conductor pattern including a second plurality of contact pads is formed on a back surface of the interposer. The first plurality of contact pads is directly connected to respective contact pads of the second plurality of contact pads. A perimeter of the acoustic resonator chip is sealed to a perimeter of the interposer.

Piston mode Lamb wave resonators are disclosed. A piston mode Lamb wave resonator can include a piezoelectric layer, such as an aluminum nitride layer, and an interdigital transducer on the piezoelectric layer. The piston mode Lamb wave resonator has an active region and a border region, in which the border region has a velocity with a lower magnitude than a velocity of the active region. The border region can suppress a transverse mode.

RF filtering circuitry comprises a first node, a second node, and a series signal path between the first node and the second node. A number of acoustic resonators are coupled to one or more of the first node and the second node via the series signal path. A first one of the acoustic resonators is associated with a first quality factor and a first electromechanical coupling coefficient. A second one of the acoustic resonators is associated with a second quality factor and a second electromechanical coupling coefficient. The first quality factor is different from the second quality factor and the first electromechanical coupling coefficient is different from the second electromechanical coupling coefficient.

Acoustic resonators, filters, and methods. An acoustic resonator includes a substrate, a piezoelectric plate, and a diaphragm including a portion of the piezoelectric plate spanning a cavity in a substrate. An interdigital transducer (IDT) on a front surface of the piezoelectric plate includes first and second sets of interleaved interdigital transducer (IDT) fingers extending from first and second busbars respectively. The interleaved IDT fingers extend onto the diaphragm. Overlapping portions of the interleaved IDT fingers define an aperture of the acoustic resonator. First and second dielectric strips are on the front surface of the piezoelectric plate. Each dielectric strip has a first portion under the IDT fingers in a respective margin of the aperture and a second portion extending into a gap between the respective margin and the respective busbar.