An acoustic wave device includes an IDT electrode on a piezoelectric layer. The IDT electrode includes first and second electrode fingers made of an alloy film including Al and at least one of Cu, Mg, Ag, or Nd, and an overlap region in which the first and second electrode fingers overlap when viewed in the direction of propagation of acoustic waves. The overlap region includes a central region and first and second edge regions outside the central region on opposite sides in the direction in which the first and second electrode fingers extend. In at least one of the first and second electrode fingers, a concentration of the at least one of Cu, Mg, Ag, or Nd in at least a portion of the first and second edge regions is higher than that in the central region.

A surface acoustic wave filter includes series and parallel arm resonance sections. The series arm resonance section is in a series arm. The parallel arm resonance section is in a parallel arm. The series arm resonance section includes one or more surface acoustic wave devices. Each surface acoustic wave device includes a first resonator group and a second resonator group. The first and second resonator groups are connected in parallel and include surface acoustic wave resonators. The first resonator group includes at least one surface acoustic wave resonator. The second resonator group includes a greater number of surface acoustic wave resonators than the at least one surface acoustic wave resonator in the first resonator group. The resonant frequency of the surface acoustic wave resonator in the first resonator group is higher than the resonant frequency of the surface acoustic wave resonators in the second resonator group.

An acoustic wave device includes a piezoelectric substrate, and an IDT electrode on the piezoelectric substrate, and the IDT electrode includes an intersection region in which first and second electrode fingers overlap each other in an acoustic wave propagation direction, the intersection region includes a central region and first and second low acoustic velocity regions outside the central region on respective sides in an extending direction of the first and second electrode fingers, first and second busbars include first and second cavities, respectively, first and second inner busbar portions on one side of the first and second cavities, and first and second outer busbar portions on another side are connected by first and second connecting portions, and at least one of the first connecting portions and at least one of the second connecting portions are a first wide width connecting portion and a second wide width connecting portion having a width wider than that of each of remaining first and second connecting portions.

Due to strong needs to reduce the dimensions and the cost of the RF filters and to reduce the number of filters required in an mobile handsets and wireless system covering numbers of operation bands, tunable RF filters which can cover as many bands or frequency ranges as possible are needed so that the number of filters can be reduced in the mobile handsets and wireless systems. This invention provides tunable surface acoustic wave resonators and filters utilizing semiconducting piezoelectric layers having embedded or elevated electrode doped regions. Both metallization ratio and loading mass are changed by varying a DC biasing voltage to effect a change in the resonant frequency of the tunable SAW devices.

Surface acoustic wave devices and related methods. In some embodiments, a surface acoustic wave device for providing resonance of a surface acoustic wave having a wavelength λ can include a quartz substrate and a piezoelectric plate formed from LiTaO.sub.3 or LiNbO.sub.3 disposed over the quartz substrate. The piezoelectric plate can have a thickness greater than 2λ. The surface acoustic wave device can further include an interdigital transducer electrode formed over the piezoelectric plate. The interdigital transducer electrode can have a mass density ρ in a range 1.50 g/cm.sup.3<ρ≤6.00 g/cm.sup.3, 6.00 g/cm.sup.3<ρ≤12.0 g/cm.sup.3, or 12.0 g/cm.sup.3<ρ≤23.0 g/cm.sup.3, and a thickness greater than 0.148λ, greater than 0.079λ, or greater than 0.036λ, respectively.

An acoustic wave device comprises a substrate including a piezoelectric material, and interdigital transducer (IDT) electrodes disposed on a surface of the substrate. The IDT electrodes have gap regions, edge regions, and center regions. A maximum width of the IDT electrodes in the gap regions is greater than the maximum width of the IDT electrodes in the edge regions, thereby achieving a velocity of an acoustic wave in the gap regions being greater than the velocity of the acoustic wave in the center regions, and the velocity of the acoustic wave in the center regions being greater than the velocity of the acoustic wave in the edge regions.

An elastic wave element having a piezoelectric substrate equipped with a first main surface, and an excitation electrode arranged on the first main surface and having multiple electrode fingers, wherein, in a cross-sectional view in the direction orthogonal to the first main surface, the width of the electrode fingers at a first height at a distance from the first main surface is greater than the width at a second height located closest to the first main surface.

An acoustic wave device that has a better TCF and can improve a resonator Q or impedance ratio is provided. The acoustic wave device includes a substrate 11 containing 70 mass % or greater of silicon dioxide (SiO.sub.2), a piezoelectric thin film 12 including LiTaO.sub.3 crystal or LiNbO.sub.3 crystal and disposed on the substrate 11, and an interdigital transducer electrode 13 disposed in contact with the piezoelectric thin film 12.

A filter device utilizing surface acoustic waves includes one or more series arm resonators connected to each other along a path between a first input/output terminal and a second input/output terminal, and three or more parallel arm resonators each connected between a connection node provided on the path and ground and defining the pass band of the filter device. Parallel arm resonators having different anti-resonant frequencies from each other are included. Parallel arm resonators among the three or more parallel arm resonators are connected to the same connection node provided along the path. Remaining parallel arm resonators are connected to different connection nodes from the same connection node. The anti-resonant frequencies of the parallel arm resonators connected to the same connection node are identical and are the lowest anti-resonant frequencies among the anti-resonant frequencies of the three or more parallel arm resonators.

A composite filter device includes a first filter and a plurality of second filters with different passbands. End portions of the first filter and the plurality of second filters are connected to a common connection. The first filter includes a piezoelectric substrate made of LiNbO.sub.3, an IDT electrode provided on the piezoelectric substrate, and a dielectric layer provided on the piezoelectric substrate so as to cover the IDT electrode. The first filter utilizes a fundamental wave of Rayleigh waves. The passband of the first filter is arranged in a frequency band that is lower than any of the passbands of the plurality of second filters.