An acoustic wave device includes a piezoelectric body including first and second main surfaces facing each other, an IDT electrode provided on the first main surface of the piezoelectric body and including electrode fingers, a high acoustic velocity member on the second main surface side of the piezoelectric body, in which an acoustic velocity of a propagating bulk wave is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric body, and a first dielectric film provided on an upper surface of the electrode fingers, in which a portion where a dielectric is not present is provided between the electrode fingers of the IDT electrode.

In an acoustic wave device, an antenna end resonator electrically closest to a first terminal is a first acoustic wave resonator. In each of the first acoustic wave resonator and a second acoustic wave resonator, a thickness of a piezoelectric layer is equal to or less than about 3.5λ. A cut angle of the piezoelectric layer of the first acoustic wave resonator is within a range of θ.sub.B±4°. The cut angle of the piezoelectric layer of the second acoustic wave resonator has a larger difference from θ.sub.B (°) than the cut angle of the piezoelectric layer of the first acoustic wave resonator.

A longitudinally coupled resonator type surface acoustic wave filter includes a high-acoustic-velocity member, a low-acoustic-velocity film provided on the high-acoustic-velocity member, a piezoelectric film provided on the low-acoustic-velocity film, a plurality of interdigital transducers provided on the piezoelectric film and along a propagation direction of a surface acoustic wave and each including a plurality of electrode fingers, and reflectors arranged such that the interdigital transducers are interposed therebetween from both sides in the propagation direction of the surface acoustic wave. An electrode finger pitch is uniform or substantially uniform in each of the interdigital transducers. When a wavelength determined by the electrode finger pitch in the reflector is defined as λ, an inter-electrode finger center distance that is an interval between each of the interdigital transducers and the interdigital transducer adjacent thereto is not shorter than about 0.25λ and not longer than about 0.37λ.

The present invention discloses a type of ultra-wide band SAW filter which comprises a first SAW resonator group and a second SAW resonator group that are connected to form a ladder structure. Each SAW resonator in the said first SAW resonator group has the same film thickness; each SAW resonator in the said second SAW resonator group has the same film thickness; the film thickness of each SAW resonator in the said first SAW resonator group is the same as or different from the film thickness of each SAW resonator in the said second SAW resonator group. The SAW filter according to the present invention can realize the pass-band non-parasitic mode response and is a high-performance ultra-wide band filter with a bandwidth of 6-20% of the center frequency and an insertion loss of less than 2 dB, and the present invention features small size, low cost and a broad application prospect in the field of military and civilian communications equipment.

An acoustic wave filter includes a series-arm resonator, a first parallel-arm resonator, and a second parallel-arm resonator. The series-arm resonator is disposed on a path connecting first and second input/output terminals. The first parallel-arm resonator is disposed on a path that connects ground with a node, which is located on a path connecting the series-arm resonator with the first input/output terminal. The second parallel-arm resonator is disposed on a path that connects ground with a node, which is located on a path connecting the series-arm resonator with the second input/output terminal. The parallel-arm resonator has a resonant frequency lower than the resonant frequency of the second parallel-arm resonator. The first parallel-arm resonator has an anti-resonant frequency higher than the anti-resonant frequency of the second parallel-arm resonator. The second parallel-arm resonator has the highest resonant frequency of all the parallel-arm resonators.

An acoustic wave filter includes a series-arm resonator, a first parallel-arm resonator, and a second parallel-arm resonator. The series-arm resonator is disposed on a path connecting first and second input/output terminals. The first parallel-arm resonator is disposed on a path that connects ground with a node, which is located on a path connecting the series-arm resonator with the first input/output terminal. The second parallel-arm resonator is disposed on a path that connects ground with a node, which is located on a path connecting the series-arm resonator with the second input/output terminal. The parallel-arm resonator has a resonant frequency lower than the resonant frequency of the second parallel-arm resonator. The first parallel-arm resonator has an anti-resonant frequency higher than the anti-resonant frequency of the second parallel-arm resonator. The second parallel-arm resonator has the highest resonant frequency of all the parallel-arm resonators.

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.

Surface acoustic wave device having mass-loaded electrode. In some embodiments, a surface acoustic wave device for providing resonance of a surface acoustic wave having a wavelength 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 2. 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 p in a range 1.50 g/cm.sup.3<6.00 g/cm.sup.3, 6.00 g/cm.sup.3<12.0 g/cm.sup.3, or 12.0 g/cm.sup.3<23.0 g/cm.sup.3, and a thickness greater than 0.148, greater than 0.079, or greater than 0.036, respectively.

An acoustic wave filter includes a substrate having piezoelectricity, input/output terminals on the substrate, ground terminals on the substrate and separated from each other, and a longitudinally coupled resonator on the substrate and arranged on a path connecting the input/output terminals, in which each of IDT electrodes included in the longitudinally coupled resonator includes a pair of comb-shaped electrodes each of which is provided with a plurality of electrode fingers and a busbar electrode, the other of the pair of the comb-shaped electrodes included in the IDT electrode arranged at a position closest to the input/output terminal is connected to the ground terminal on the substrate, and the other of the pair of comb-shaped electrodes included in each of all the IDT electrodes other than the IDT electrode is connected to the ground terminal on the substrate.

A surface acoustic wave device includes a piezoelectric material layer, a pair of busbars, a plurality of electrode fingers, and reflectors. The piezoelectric material layer has a thickness that is in a range of 1 to 2.5 times of an acoustic wavelength. A main mode of an elastic wave excited on the piezoelectric material layer by the electrode fingers is a leaky surface acoustic wave. A design variable is set such that a minimum propagation loss frequency where a propagation loss becomes minimum and a frequency of a plate wave spurious formed due to a slow shear wave excited together with the leaky surface acoustic wave are matched. A propagation velocity of a slowest bulk wave of an elastic wave that propagates in a lower layer of the piezoelectric material layer is equal to or more than 1.05 times of a velocity of the leaky surface acoustic wave.