An acoustic wave device is disclosed. The acoustic wave device includes a piezoelectric layer, an interdigital transducer electrode positioned over the piezoelectric layer, and an anti-refection layer over a conductive layer of the interdigital transducer electrode. The conductive layer can include aluminum, for example. The anti-reflection layer can include silicon. The anti-reflection layer can be free from a material of the interdigital transducer electrode. The acoustic wave device can further include a temperature compensation layer positioned over the anti-reflection layer in certain embodiments.

A multiplexer includes N acoustic wave filters each including one end connected in common and having a different pass band, in which when the N acoustic wave filters are in order from a side of a lower frequency of the pass band, at least one n-th acoustic wave filter among the N acoustic wave filters excluding an acoustic wave filter having the highest frequency of the pass band includes one or more acoustic wave resonators including a support substrate, a silicon nitride film laminated on the support substrate, a silicon oxide film laminated on the silicon nitride film, a piezoelectric body laminated on the silicon oxide film, and an IDT electrode provided on the piezoelectric body. All acoustic wave filters having a pass band in a higher frequency than a frequency of a pass band of the n-th acoustic wave filter satisfy f.sub.h1_t.sup.(n)>f.sub.u.sup.(m) or f.sub.h1_t.sup.(n)<f.sub.l.sup.(m).

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.

Methods of manufacturing an acoustic wave device are disclosed. An anti-reflection layer can be formed over a conductive layer that is over a piezoelectric layer. The conductive layer can include aluminum, for example. The anti-reflection layer can remain distinct from the conductive layer after a heating process. A photolithography process can pattern an interdigital transducer of the acoustic wave device from one or more interdigital transducer electrode layers that include the conductive layer. The anti-reflection layer can reduce reflection from the conductive layer during the photolithography process.

Systems, methods, and devices for reducing insertion loss and/or swapping transmitter (TX) and receiver (RX) frequencies in an electrical balance duplexer (EBD) used in a transceiver device for frequency division duplexing (FDD) applications are provided. Feed-forward receiver path from the antenna to a low noise amplifier (LNA) and a feed-forward path from the antenna to a power amplifier (PA) of the EBD may be used for reducing insertion loss of the RX and TX signals. In some embodiments, switches may be used to selectively alter operational modes for varied levels of isolation and/or swapping of TX and RX frequencies.

An acoustic wave device includes: a first substrate having a first surface and a side surface; an acoustic wave resonator located on the first surface of the first substrate; and a first insulator film that covers the acoustic wave resonator and is in contact with at least a part, which is located closer to the first surface, of the side surface of the first substrate.

A surface elastic wave resonator comprises a piezoelectric material to propagate the surface elastic waves and a transducer inserted between a pair of reflectors comprising combs of interdigitated electrodes and having a number Nc of electrodes connected to a hot spot and an acoustic aperture W wherein the relative permittivity of the piezoelectric material is greater than about 15, a product of Nc.Math.W/fa for the transducer being greater than 100 m.Math.MHz.sup.1, where fa is the antiresonance frequency of the resonator. A circuit comprises a load impedance and a resonator according to the invention and having an electrical response manifesting as a peak in the coefficient of reflection S.sub.11 at a frequency of a minimum value of the parameter S.sub.11 that is lower than 10 dB, the antiresonance peak of the resonator being matched to the impedance of the load.

A method for processing a wafer includes subjecting the wafer to a reduction treatment with heat and a reducing agent that has a melting point of lower than 600 C. The wafer is made of a material selected from the group consisting of lithium tantalate, lithium niobate, and a combination thereof. The wafer and the reducing agent are spaced apart from each other so that the reducing agent indirectly interacts with the wafer during the reduction treatment. Also disclosed is a processed wafer obtained by the method.

An acoustic wave device includes: a piezoelectric substrate; a comb-shaped electrode located on the piezoelectric substrate; a pair of reflectors located on the piezoelectric substrate, the pair of reflectors sandwiching the comb-shaped electrode; a first dielectric film located on the piezoelectric substrate, the first dielectric film covering the pair of reflectors and having side surfaces in regions between the comb-shaped electrode and the pair of reflectors; and a second dielectric film located on the piezoelectric substrate, the second dielectric film covering the comb-shaped electrode and being in contact with the side surfaces of the first dielectric film.

The present disclosure provides an apparatus that includes a plurality of filter circuits configured to filter one or more signals. The plurality of filter circuits includes a first filter component configured to have a first passband that spans adjacent transmission frequency ranges of a first communication band and a second communication band. The plurality of filter circuits further includes a second filter component having a second passband that spans a reception frequency range of a third communication band. The plurality of filter circuits further includes a third filter component having a third passband that spans adjacent reception frequency ranges of the first communication band and the third communication band. The plurality of filter circuits further includes a fourth filter component having a fourth passband that spans the second reception frequency range of the second communication band.