Abstract: A tunable filter is a ladder circuit tunable filter including serial arm resonators and a parallel arm resonator. The serial arm resonators and the parallel arm resonator include elastic wave resonators. Variable capacitors are connected in series to the serial arm resonators, a variable capacitor is connected in parallel to the parallel arm resonator, and first inductors are connected in series to the serial arm resonators. When an impedance at a resonant frequency of the serial arm resonators is Zrs and an impedance at a resonant frequency of the parallel arm resonator is Zrp, a ratio Zrs/Zrp is not greater than 1.

Abstract: An elastic wave device making use of an SH plate wave propagating in LiNbO3 substrates includes a LiNbO3 substrate, IDT electrodes located on at least one surface of the LiNbO3 substrate, and a support which is bonded to the LiNbO3 substrate such that the support is located outside a region provided with the IDT electrodes and supports the LiNbO3 substrate, wherein ? of the Euler angles (0°, ?, 0°) of the LiNbO3 substrate ranges from about 92° to about 138° and the thickness of the LiNbO3 substrate ranges from about 0.05? to about 0.25?, where ? is the wavelength determined by the pitch between electrode fingers of the IDT electrodes.

Abstract: An elastic wave device includes a first IDT electrode on a first main surface of a LiNbO3 substrate, and a second IDT electrode on a second main surface thereof. The application of alternating voltages with reversed phases to each other to the first and second IDT electrodes excites plate waves in which SH waves in a high order mode predominate. The elastic wave device uses the plate waves in the high order mode in which the SH waves predominate.

Abstract: An elastic wave device includes an IDT electrode disposed on a LiNbO3 substrate and an aluminum nitride film or a silicon nitride film is stacked to cover the IDT electrode and utilizes a leaky elastic wave. The IDT electrode includes a metal selected from a group consisting of Cu, Al, Au, Pt, and Ni. Euler angles of the LiNbO3 are (0°±5°, ?, 0°±5°), and when X denotes a wavelength-normalized thickness of the IDT electrode and Y denotes ? of the Euler angles, Y is set in a specific range depending on the range of the wavelength-normalized thickness of the IDT electrode, the range of the wavelength-normalized thickness of the aluminum nitride film or the silicon nitride film, and the kind of metal of which the IDT electrode is composed.

Abstract: A piezoelectric bulk-wave resonator has a single-crystal LiNbO3 substrate whose Euler Angles are in the ranges of about (78° to 106°, 78° to 104°, 18° to 53°), a first driver electrode on a first main surface of the single-crystal LiNbO3 substrate, and a second driver electrode on a second main surface. The first driver electrode and the second driver electrode overlap with the single-crystal LiNbO3 substrate therebetween. The piezoelectric bulk-wave resonator uses the thickness-shear mode.

Abstract: A tunable filter is a ladder circuit tunable filter including serial arm resonators and a parallel arm resonator. The serial arm resonators and the parallel arm resonator include elastic wave resonators. Variable capacitors are connected in series to the serial arm resonators, a variable capacitor is connected in parallel to the parallel arm resonator, and first inductors are connected in series to the serial arm resonators. When an impedance at a resonant frequency of the serial arm resonators is Zrs and an impedance at a resonant frequency of the parallel arm resonator is Zrp, a ratio Zrs/Zrp is not greater than 1.

Abstract: A variable capacitance element includes a piezoelectric substrate, a buffer layer located on the piezoelectric substrate with an orientation, a dielectric layer located on the buffer layer and having a relative dielectric constant that varies in accordance with an applied voltage, and a first electrode and a second electrode arranged to apply an electric field to the dielectric layer.

Abstract: An elastic wave device includes a piezoelectric substrate and an interdigital transducer electrode disposed in a piezoelectric vibrating portion of the piezoelectric substrate to pass through the piezoelectric substrate.

Abstract: A tunable filter device includes a first tunable filter with a first pass band, and a second tunable filter connected to the first tunable filter and having a second pass band located within the first pass band and a band width narrower than the band width of the first pass band. The second tunable filter includes a local oscillator that generates a predetermined frequency signal, a mixer that outputs a sum of and a difference between an output signal of the first tunable filter and the predetermined frequency signal output from the local oscillator, and an IF tunable filter connected to the mixer.

Abstract: A piezoelectric bulk-wave resonator has a single-crystal LiNbO3 substrate whose Euler Angles are in the ranges of about (78° to 106°, 78° to 104°, 18° to 53°), a first driver electrode on a first main surface of the single-crystal LiNbO3 substrate, and a second driver electrode on a second main surface. The first driver electrode and the second driver electrode overlap with the single-crystal LiNbO3 substrate therebetween. The piezoelectric bulk-wave resonator uses the thickness-shear mode.

Abstract: A surface acoustic wave device includes a piezoelectric substrate, at least one interdigital transducer (IDT) electrode provided on the piezoelectric substrate, and an insulator layer to improve a temperature characteristic arranged so as to cover the IDT electrode. When a surface of the insulator layer is classified into a first surface region under which the IDT electrode is positioned and a second surface region under which no IDT electrode is positioned, the surface of the insulator layer in at least one portion of the second surface region is higher than the surface of the insulator layer from the piezoelectric substrate in at least one portion of the first surface region by at least about 0.001?, where the wavelength of an acoustic wave is ?.

Abstract: An elastic wave device making use of an SH plate wave propagating in LiNbO3 substrates includes a LiNbO3 substrate, IDT electrodes located on at least one surface of the LiNbO3 substrate, and a support which is bonded to the LiNbO3 substrate such that the support is located outside a region provided with the IDT electrodes and supports the LiNbO3 substrate, wherein ? of the Euler angles (0°, ?, 0°) of the LiNbO3 substrate ranges from about 92° to about 138° and the thickness of the LiNbO3 substrate ranges from about 0.05? to about 0.25?, where ? is the wavelength determined by the pitch between electrode fingers of the IDT electrodes.

Abstract: A surface acoustic wave device includes a piezoelectric substrate made of lithium niobate and including grooves in a surface thereof. Each groove includes a finger of an IDT electrode made of copper. The IDT electrode includes a first electrode layer embedded in the grooves and a second electrode layer sticking out of the surface of the piezoelectric substrate. A normalized electrode thickness of the first electrode layer is about 1.0% to about 12.0% inclusive, and the normalized electrode thickness of the second electrode layer is about 1.0% to about 9.0% inclusive. The normalized electrode thickness of the entire IDT electrode is about 6.0% to about 13.0% inclusive.

Abstract: A method for fabricating an acoustic wave device includes the steps of forming an insulating material layer on a piezoelectric substrate, forming a patterned photoresist on the insulating material layer, patterning the insulating material layer, and forming a piezoelectric-substrate exposed depression corresponding to a region where an interdigital transducer electrode is to be formed on a first insulator layer composed of the insulating material layer, depositing a metallic material on the piezoelectric substrate to form the interdigital transducer electrode in the piezoelectric-substrate exposed depression such that the overall interdigital transducer electrode is thinner than the first insulator layer and coating the photoresist with a metallic material, removing the photoresist and the metallic material on the photoresist, and depositing a second insulator layer so as to cover the interdigital transducer electrode and the first insulator layer.

Abstract: A sensor for detecting a substance in liquid includes a sensing circuit including a sensing surface acoustic wave (SAW) element in which a reaction film to react with a substance in liquid, a reference circuit including a reference SAW element including an IDT and not including a reaction film, a first signal source driving the sensing circuit, a second signal source driving the reference circuit and being independent of the first signal source, and a differential circuit arranged to output a differential output between an output of the sensing circuit and an output of the reference circuit. The frequency of a first frequency signal output from the first signal source is different from the frequency of a second frequency signal output from the second signal source, thereby making a driving frequency for the sensing SAW element and a driving frequency for the reference SAW element substantially the same as or different from one another.

Abstract: A variable capacitance element includes a piezoelectric substrate, a buffer layer located on the piezoelectric substrate with an orientation, a dielectric layer located on the buffer layer and having a relative dielectric constant that varies in accordance with an applied voltage, and a first electrode and a second electrode arranged to apply an electric field to the dielectric layer.

Abstract: A surface acoustic wave device includes a piezoelectric substrate made of lithium niobate and including grooves in a surface thereof. Each groove includes a finger of an IDT electrode made of copper. The IDT electrode includes a first electrode layer embedded in the grooves and a second electrode layer sticking out of the surface of the piezoelectric substrate. A normalized electrode thickness of the first electrode layer is about 1.0% to about 12.0% inclusive, and the normalized electrode thickness of the second electrode layer is about 1.0% to about 9.0% inclusive. The normalized electrode thickness of the entire IDT electrode is about 6.0% to about 13.0% inclusive.

Abstract: A tunable filter that is capable of magnifying a pass band width or increasing a frequency variable amount includes a resonator circuit portion provided in at least one of a series arm connecting an input terminal and an output terminal to each other and a parallel arm connecting the series arm and a ground potential to each other, a first variable capacitor is connected in series to the resonator circuit portion and a second variable capacitor is connected in parallel to the resonator circuit portion. The resonator circuit portion includes a piezoelectric substrate including LiNbO3 or LiTaO3, an elastic wave resonator including an electrode located on the piezoelectric substrate, and a bandwidth extending inductance Lx, Lx connected to the elastic wave resonator.

Abstract: A surface acoustic wave device prevents a decrease in yield and a decrease in reliability, such as an impulse withstand voltage, and achieves good frequency characteristics, even when using higher frequencies. The surface acoustic wave device includes an IDT electrode disposed on a piezoelectric substrate, and a first insulating film and at least one second insulating film disposed on the IDT electrode, and utilizes a higher-order mode of an SH wave, in which the acoustic velocity of a surface acoustic wave in the first insulating film located closer to the IDT electrode than the insulating film at an outermost surface is higher than the acoustic velocity of a surface acoustic wave in the second insulating film located at the outermost surface.

Abstract: An inexpensive surface acoustic wave device that increases an acoustic velocity of a surface acoustic wave and an electromechanical coupling coefficient includes a piezoelectric substrate in which a LiNbO3 single-crystal plate having Euler angles (0°, 67° to 160°, ?5° to +5°) or (90°, 51° to 133°, ?5° to +5°) is provided on a high acoustic-velocity substrate in which an acoustic velocity of a transverse wave is in a range of about 5400 m/sec to about 8660 m/sec or lower, and an electrode provided on the piezoelectric substrate and made of metal.