An elastic wave device includes a support substrate made of silicon, a piezoelectric film disposed directly or indirectly on the support substrate, and an interdigital transducer electrode disposed on one surface of the piezoelectric film. A higher-order mode acoustic velocity of propagation through the piezoelectric film is equal or substantially equal to an acoustic velocity V.sub.si=(V.sub.1).sup.1/2 of propagation through silicon or higher than the acoustic velocity V.sub.si, where V.sub.si is specified by V.sub.1 among solutions V.sub.1, V.sub.2, and V.sub.3 with respect to x derived from Ax.sup.3+Bx.sup.2+Cx+D=0.

An elastic wave device includes a support substrate made of silicon, a piezoelectric film disposed directly or indirectly on the support substrate, and an interdigital transducer electrode disposed on one surface of the piezoelectric film. A higher-order mode acoustic velocity of propagation through the piezoelectric film is equal or substantially equal to an acoustic velocity V.sub.si=(V.sub.1).sup.1/2 of propagation through silicon or higher than the acoustic velocity V.sub.si, where V.sub.si is specified by V.sub.1 among solutions V.sub.1, V.sub.2, and V.sub.3 with respect to x derived from Ax.sup.3+Bx.sup.2+Cx+D=0.

An elastic wave device includes an LiNbO.sub.3 substrate, a first elastic wave resonator including a first IDT electrode and a first dielectric film, and a second elastic wave resonator including a second IDT electrode and a second dielectric film. A Rayleigh wave travels along at least one surface of the elastic wave device. A thickness of the first dielectric film differs from a thickness of the second dielectric film. A propagation direction of an elastic wave in the first elastic wave resonator coincides with a propagation direction of an elastic wave in the second elastic wave resonator. Euler angles of the LiNbO.sub.3 substrate fall within a range of (0°±5°, θ, 0°±10°).

An elastic wave device includes an LiNbO.sub.3 substrate, a first elastic wave resonator including a first IDT electrode and a first dielectric film, and a second elastic wave resonator including a second IDT electrode and a second dielectric film. A Rayleigh wave travels along at least one surface of the elastic wave device. A thickness of the first dielectric film differs from a thickness of the second dielectric film. A propagation direction of an elastic wave in the first elastic wave resonator coincides with a propagation direction of an elastic wave in the second elastic wave resonator. Euler angles of the LiNbO.sub.3 substrate fall within a range of (0°±5°, θ, 0°±10°).

A high-frequency apparatus includes a resin substrate, a first device including a substrate and provided on the resin substrate, and a second device provided adjacent to the first device on the resin substrate. Each of the first device and the second device includes an acoustic wave device. The second device includes a piezoelectric substrate and a functional element provided on the piezoelectric substrate. The substrate of the first device includes Si or a laminated material including Si. The piezoelectric substrate of the second device includes LiTaO.sub.3, LiNbO.sub.3, or a laminated material including LiTaO.sub.3 or LiNbO.sub.3. The resin substrate includes glass.

A high-frequency apparatus includes a resin substrate, a first device including a substrate and provided on the resin substrate, and a second device provided adjacent to the first device on the resin substrate. Each of the first device and the second device includes an acoustic wave device. The second device includes a piezoelectric substrate and a functional element provided on the piezoelectric substrate. The substrate of the first device includes Si or a laminated material including Si. The piezoelectric substrate of the second device includes LiTaO.sub.3, LiNbO.sub.3, or a laminated material including LiTaO.sub.3 or LiNbO.sub.3. The resin substrate includes glass.

A radio-frequency module includes a mounting substrate, a first filter, a second filter, a shield layer, and a conductor. The mounting substrate has a first main surface and a second main surface on opposite sides. The shield layer is disposed on an outer surface of a resin layer with which the first filter and the second filter are covered. The radio-frequency module is capable of performing simultaneous transmission by using both the first filter and the second filter. The conductor is disposed on the first main surface of the mounting substrate and is in contact with the transmitting filter and the mounting substrate. The conductor is in contact with the shield layer on a side other than a side closer to the second filter than to the first filter.

A circuit comprising a receive block, a transmit block, and an antenna multiplexer. The antenna multiplexer includes an input port coupled to the transmit block, an output port coupled to the receive block, a common port for coupling to an antenna, and a receive filter coupled between the common port and the output port. The receive filter includes a first plurality of resonators coupled together in series between the common port and the output port including a compensation resonator coupled directly to the output port. A first angular range of a reflection coefficient of the antenna multiplexer over a transmission frequency band measured looking into the output port of the antenna multiplexer does not overlap with a second angular range of the conjugate of the reflection coefficient of the low noise amplifier over the transmission frequency band measured looking into an input of the low noise amplifier.

A circuit comprising a receive block, a transmit block, and an antenna multiplexer. The antenna multiplexer includes an input port coupled to the transmit block, an output port coupled to the receive block, a common port for coupling to an antenna, and a receive filter coupled between the common port and the output port. The receive filter includes a first plurality of resonators coupled together in series between the common port and the output port including a compensation resonator coupled directly to the output port. A first angular range of a reflection coefficient of the antenna multiplexer over a transmission frequency band measured looking into the output port of the antenna multiplexer does not overlap with a second angular range of the conjugate of the reflection coefficient of the low noise amplifier over the transmission frequency band measured looking into an input of the low noise amplifier.

A piezoelectric device includes a support substrate, an intermediate layer on the support substrate, a piezoelectric layer on the intermediate layer, a functional element on the piezoelectric layer, an insulation layer, and a wiring electrode. The insulation layer is on the support substrate and in contact with the intermediate layer and the piezoelectric layer. The wiring electrode extends from a top of the insulation layer to a top of the piezoelectric layer and is connected to the functional element. The insulation layer includes first and second regions. The first region is thinner than a thickness of the multilayer body. The second region connects the first region and the multilayer body, and includes a portion slanted from the first region toward an upper surface of the piezoelectric layer. The second region of the insulation layer does not extend to the top of the piezoelectric layer.