Embodiments of a Surface Acoustic Wave (SAW) device having a guided SAW structure that provides spurious mode suppression and methods of fabrication thereof are disclosed. In some embodiments, a SAW device includes a non-semiconductor support substrate, a piezoelectric layer on a surface of the non-semiconductor support substrate, and at least one interdigitated transducer on a surface of the piezoelectric layer opposite the non-semiconductor support substrate. A thickness of the piezoelectric layer, a SAW velocity of the piezoelectric layer, and an acoustic velocity of the non-semiconductor support substrate are such that a frequency of spurious modes above a resonance frequency of the SAW device is above a bulk wave cut-off frequency of the SAW device. In this manner, the spurious modes above the resonance frequency of the SAW device are suppressed.

A transducer for SAW-type or PSAW-type acoustic waves is proposed in which the dielectric (DK) is applied onto the substrate so that the gap (GP) between the ends of the electrode fingers and the opposite bus electrode is completely filled with said dielectric (DK), but the active area of the transducer, thus transversal overlap area (UB) of the electrode fingers, is not covered by said dielectric.

An elastic wave device includes a piezoelectric substrate, a first elastic wave element on the piezoelectric substrate and including at least one first interdigital transducer electrode and a first reflector in an area of the first interdigital transducer electrode at one side in a propagation direction of elastic waves, and a second elastic wave element on the piezoelectric substrate and including at least one second interdigital transducer electrode and a second reflector in an area of the second interdigital transducer electrode at one side in the propagation direction of elastic waves. The first and second reflectors are disposed side by side in the propagation direction. A reflection member, between the first and second reflectors, reflects elastic waves in at least a direction different from the propagation direction.

The present disclosure relates to acoustic wave devices, and particularly to high quality factor (Q) transducers for surface acoustic wave (SAW) devices. An exemplary SAW device includes an interdigital transducer (IDT) between two reflective gratings to form a resonator. The resonator operates through shear horizontal mode acoustic waves, and therefore suppression of transverse modes (parallel to electrode fingers of the IDT) is desired. A piston mode can be formed in the resonator to suppress transverse modes, which may also increase energy leakage and result in a lower Q. A higher Q is achieved by adding a fast region at an end of one or more of the electrode fingers of the IDT.

An apparatus is disclosed for a surface-acoustic-wave filter with an electrical conductor having a floating potential. In an example aspect, the apparatus includes a surface-acoustic-wave filter with a piezoelectric layer and an electrode structure disposed on a surface of the piezoelectric layer. The electrode structure includes a first comb-shaped structure and a second comb-shaped structure. The electrode structure also includes at least one electrical conductor positioned between the first comb-shaped structure and the second comb-shaped structure such that a gap separates the at least one electrical conductor from the first comb-shaped structure and the second comb-shaped structure.

Embodiments of a Surface Acoustic Wave (SAW) device having a guided SAW structure that provides spurious mode suppression and methods of fabrication thereof are disclosed. In some embodiments, a SAW device includes a non-semiconductor support substrate, a piezoelectric layer on a surface of the non-semiconductor support substrate, and at least one interdigitated transducer on a surface of the piezoelectric layer opposite the non-semiconductor support substrate. A thickness of the piezoelectric layer, a SAW velocity of the piezoelectric layer, and an acoustic velocity of the non-semiconductor support substrate are such that a frequency of spurious modes above a resonance frequency of the SAW device is above a bulk wave cut-off frequency of the SAW device. In this manner, the spurious modes above the resonance frequency of the SAW device are suppressed.

A filter device having a pass band and a stop band on a lower frequency side than the pass band includes a filter having a pass band including the pass band, a series arm resonator connected in series to the filter, a first inductor directly connected in series to the series arm resonator, and a parallel arm resonator connected between a node on a path connecting the filter and the series arm resonator and the ground. The parallel arm resonator constitutes a resonance circuit having a resonant frequency at which an attenuation pole corresponding to a high frequency end of the first stop band, and the series arm resonator and the inductor constitute a resonance circuit having an anti-resonant frequency on a lower frequency side than the pass band and having a sub-resonant frequency higher than a resonant frequency of the resonance circuit.

An acoustic wave device includes a first and second element substrates each having piezoelectricity, and bonding layers bonding the first and second element substrates to each other. First and second IDT electrodes and first and second wiring electrodes are respectively provided on the first and second element substrates. The first and second wiring electrodes are disposed one above the other with the bonding layer interposed therebetween to define a wiring electrode overlapped portion. In each of the wiring electrode overlapped portions, the first wiring electrode and the second wiring electrode are provided in one of combinations in which one wiring electrode is a signal wiring electrode and the other wiring electrode is a ground wiring electrode, both of the wiring electrodes are ground wiring electrodes, and both of the wiring electrodes are signal wiring electrodes at the same potential.

The present disclosure relates to acoustic wave devices, and particularly to high quality factor (Q) transducers for surface acoustic wave (SAW) devices. An exemplary SAW device includes an interdigital transducer (IDT) between two reflective gratings to form a resonator. The resonator operates through shear horizontal mode acoustic waves, and therefore suppression of transverse modes (parallel to electrode fingers of the IDT) is desired. A piston mode can be formed in the resonator to suppress transverse modes, which may also increase energy leakage and result in a lower Q. A higher Q is achieved by adding a fast region at an end of one or more of the electrode fingers of the IDT.

An elastic wave device includes a piezoelectric substrate mainly including lithium niobate, an interdigital transducer electrode provided on the piezoelectric substrate, and a dielectric film, provided on the piezoelectric substrate and covering the interdigital transducer electrode, and mainly including silicon oxide. The elastic wave device uses a Rayleigh wave. The interdigital transducer electrode includes main electrode layers that include one or more first main electrode layer made of a metal with a C11.sup.2/C12 ratio greater than the C11.sup.2/C12 ratio of the silicon oxide with regard to the elastic constants C11 and C12. The sum of the thicknesses of the one or more first main electrode layers is about 55% or more based on the thickness of the whole interdigital transducer electrode is about 100%.