Certain aspects of the present disclosure provide a surface acoustic wave (SAW) resonator with piston mode design and electrostatic discharge (ESD) protections. An example electroacoustic device generally includes a piezoelectric material and a first electrode structure disposed above the piezoelectric material. The first electrode structure comprises first electrode fingers arranged within an active region having a first region and a second region. At least one of the first electrode fingers has at least one of a different width or a different height in the first region than in the second region, and the first electrode fingers comprise a first electrode finger that has a width or height in the second region that is less than a corresponding width or height of the at least one of the first electrode fingers in the second region.

There are disclosed acoustic resonators and method of fabricating acoustic resonators. An acoustic resonator includes a single-crystal piezoelectric plate having front and back surfaces, the back surface attached to a surface of a substrate except for portions of the piezoelectric plate forming a diaphragm spanning a cavity in the substrate. A conductor pattern on the front surface includes an interdigital transducer (IDT) with interleaved fingers of the IDT disposed on the diaphragm. A periodic array of holes is provided in the diaphragm.

An acoustic wave device includes a piezoelectric layer and an interdigital transducer electrode disposed over the piezoelectric layer. The interdigital transducer electrode is thicker in a center region of the interdigital transducer electrode than in a gap region of the interdigital transducer electrode to thereby reduce a mass loading of the interdigital transducer electrode in the gap region. The interdigital transducer electrode has a layer of more dense material disposed of a layer of less dense material.

An acoustic wave device includes a piezoelectric layer and an interdigital transducer electrode disposed over the piezoelectric layer. The interdigital transducer electrode is thicker in a center region of the interdigital transducer electrode than in a gap region of the interdigital transducer electrode to thereby reduce a mass loading of the interdigital transducer electrode in the gap region. The interdigital transducer electrode has a layer of less dense material disposed of a layer of more dense material.

An acoustic wave filter includes a piezoelectric layer. A first acoustic wave device includes a portion of the piezoelectric layer and a first multi-layer interdigital transducer electrode disposed over the first portion of the piezoelectric layer. Additional acoustic wave devices are coupled to the first acoustic wave device, the additional acoustic wave devices including a second portion of the piezoelectric layer and a plurality of multi-layer interdigital transducer electrodes disposed over the second portion of the piezoelectric layer. At least one of the plurality of multi-layer interdigital transducer electrodes includes a layer that is thinner than a corresponding layer of the same material of the first multi-layer interdigital transducer electrode of the first acoustic wave device.

An acoustic wave device comprises a substrate including a piezoelectric material, interdigital transducer (IDT) electrodes disposed on an upper surface of the substrate. The IDT electrodes having gap regions, edge regions, and center regions. A duty factor of the IDT electrodes in the edge regions is greater than the duty factor of the IDT electrodes in the center regions. A first dielectric film is disposed above the IDT electrodes and an upper surface of the substrate. The first dielectric film has a greater thickness in portions of the center regions than in portions proximate the gap regions.

An acoustic wave device includes a dielectric film covering an IDT electrode. The IDT electrode includes first and second edge regions and first and second high acoustic velocity regions. The first and second edge regions are low acoustic velocity regions. The first and second high acoustic velocity regions are on outer sides of an intersecting width region where first and second electrode fingers are adjacent to each other in an acoustic wave propagation direction. A thickness of the dielectric film on the first and second edge regions is greater than that of the dielectric film on the first and second high acoustic velocity regions.

A surface acoustic wave resonator comprises at least one set of interdigital transducer (IDT) electrodes disposed on an upper surface of a piezoelectric substrate between first and second reflector gratings, a layer of silicon nitride disposed over the at least one set of IDT electrodes and the first and second reflector gratings, and a continuous trench formed in the layer of silicon nitride over portions of bus bar electrodes and tips of electrode fingers of the at least one set of IDT electrodes and over portions of bus bar electrodes and electrode fingers of the first and second reflector gratings to reduce acoustic leakage at electrode fingers of the first and second reflector gratings proximate the at least one set of IDT electrodes.

An electro acoustic resonator is provided. The resonator has a gap short structure (GSS) to electrically short at least an area of the transversal gap to suppress transversal gap mode excitations. The gap short structure may be provided by a conductive stripe in the gap and parallel to or inclined with respect to the bus bar (BB) shorting adjacent IDT fingers. Additional connectors between the stripe and the bus bar may be provided. The connectors may have different pitch or metallization ratio with respect to the ID fingers. The connectors may be offset from the position of the fingers and my be inclined with respect to the bus bars. Multiple parallel stripes in the gap may provide a transversal reflector. By using a gap short structure a further improved transversal mode suppression of piston mode designs can be achieved.

An acoustic wave device includes a piezoelectric substrate with a reverse-velocity surface having an ellipse shape, an IDT electrode on the piezoelectric substrate, and a dielectric film on the piezoelectric substrate and covering the IDT electrode. The acoustic wave device utilizes a Love wave. The IDT electrode includes an intersecting region in which first electrode fingers and second electrode fingers are interdigitated. The intersecting region includes a central region, a first edge region and a second edge region located at both ends of the central region. When x (%) denotes a wavelength-normalized film thickness of the IDT electrode and y (g/cm.sup.3) denotes an electrode density of the IDT electrode, the wavelength-normalized film x is set at a value not less than x that satisfies Equation 1. The film thicknesses of the dielectric films in the first and second edge regions are smaller than the dielectric film in the central region.