An elastic wave device manufacturing method includes a preparing a piezoelectric wafer on which IDT electrodes are provided in elastic wave device forming portions, providing on a first main surface of the piezoelectric wafer support layers in the elastic wave device forming portions, bonding a cover member to cover the support layers to obtain a multilayer body, cutting the multilayer body in a first direction multiple times, cutting the multilayer body in a second direction orthogonal to the first direction to obtain elastic wave devices, in which a resin layer extends across a boundary between the elastic wave device forming portions adjacent to each other on the first main surface of the piezoelectric wafer, and the second cutting step is performed in a state in which the resin layer is present.

An acoustic wave device comprises an IDT electrode disposed above an upper surface of a piezoelectric substrate and includes a plurality of electrode fingers configured to excite a main acoustic wave. A first dielectric film made of an oxide is disposed above the upper surface of the piezoelectric substrate and covers the plurality of electrode fingers. A second dielectric film made of non-oxide is disposed between the first dielectric film and each of the plurality of electrode fingers. A third dielectric film is disposed between the piezoelectric substrate and the plurality of electrode fingers. A speed of a transverse wave propagating through the third dielectric film is greater than a speed of the main acoustic wave propagating through the piezoelectric substrate. The third dielectric film contacts the first dielectric film between adjacent electrode fingers of the plurality of electrode fingers.

An electronic module includes a substrate, at least one first electronic component that includes a hollow portion, at least one second electronic component that includes no hollow portion, a first sealing resin, and a second sealing resin. The at least one first electronic component is sealed with the first sealing resin. The at least one second electronic component has a narrowest pitch between the electrodes that are provided on the mounting surface, and at least the mounting surface including the electrodes of the at least one second electronic component are sealed with the second sealing resin. The volume percentage of a filler that is included in the first sealing resin is larger than the volume percentage of a filler that is included in the second sealing resin.

The multiplexer includes a plurality of IDT electrodes on a substrate, an insulating cover located on the substrate so as to configure one or more spaces above the plurality of IDT electrodes, an antenna terminal, transmission terminal, and reception terminal which are all located on the substrate and pass through the cover, and a reinforcing layer which is located on the cover and is made of metal. By the plurality of IDT electrodes, a transmission filter located in a signal path connecting the antenna terminal and the transmission terminal and a receiving filter located in a signal path connecting the antenna terminal and the reception terminal. The reinforcing layer includes a first area part facing the transmission filter and a second area part which faces the receiving filter and is separated from the first area part.

An elastic wave device includes a piezoelectric substrate made of LiNbO.sub.3, interdigital transducer electrodes on the piezoelectric substrate, and a first dielectric film provided on the piezoelectric substrate and the first dielectric film to cover the IDT electrodes and made of a silicon oxide. The IDT electrodes include a first metal film made of one metal selected from Pt, Cu, Mo, Au, W, and Ta. The Euler angles (, , ) of the piezoelectric substrate are (05, 9070, 05). The metal for the first metal film and the thickness hm/ (%) match any of the combinations as follows:

TABLE-US-00001 Metal for the first metal film Thickness hm/ (%) of the first metal film Pt 6.5 hm/ 25 Cu 13 hm/ 25 Mo 15.5 hm/ 25 Au 6.5 hm/ 25 W 7.5 hm/ 25 Ta .sup.7 hm/ 25

A first filter of a multiplexer includes serial resonators and parallel resonators that are acoustic wave resonators. A first of the serial resonators that is closer to a common terminal than the other serial resonators is connected to the common terminal without the parallel resonators interposed therebetween. Each of the elastic wave resonators includes a substrate having piezoelectricity, an IDT electrode provided on the substrate, and a dielectric layer provided on the substrate to cover the IDT electrode. A thickness of the dielectric layer of the first serial resonator is smaller than a thickness of each of the dielectric layers of the remainder of the elastic wave resonators.

An elastic wave device includes a piezoelectric thin film, IDT electrodes on the piezoelectric thin film, an insulating layer surrounding the piezoelectric thin film on a primary surface of a support substrate, a spacer layer surrounding the piezoelectric thin film in plan view, and a cover on the spacer layer. The spacer layer includes an outer edge and an inner edge closer than the outer edge to the piezoelectric thin film in plan view. The primary surface of the insulating layer closer to the spacer layer includes a sloping region that extends where the insulating layer overlaps the spacer layer in plan view and in which the distance from the first primary surface of the support substrate along the direction perpendicular or substantially perpendicular to the support substrate increases from the outer edge toward the inner edge.

A first filter of a multiplexer includes serial resonators and parallel resonators that are acoustic wave resonators. A first of the serial resonators that is closer to a common terminal than the other serial resonators is connected to the common terminal without the parallel resonators interposed therebetween. Each of the elastic wave resonators includes a substrate having piezoelectricity, an IDT electrode provided on the substrate, and a dielectric layer provided on the substrate to cover the IDT electrode. A thickness of the dielectric layer of the first serial resonator is smaller than a thickness of each of the dielectric layers of the remainder of the elastic wave resonators.

A surface acoustic wave filter includes resonators, wherein one of the resonator includes four or more regions with different pitches of electrode fingers, the pitch of electrode fingers in each of the four or more regions is constant, the pitch of electrode fingers in first regions, among the four or more regions, disposed at both ends of the resonator in a surface acoustic wave propagation direction is smaller than the pitch of electrode fingers in the regions other than the first regions, and the pitch of electrode fingers in a second region adjacent to the first region and the pitch of electrode fingers in a third region adjacent to the first region are different from each other.

A radio-frequency module includes a multi-filter unit and a switch unit. The multi-filter unit includes filters having different passbands of signals and each including input/output terminals. The switch unit includes a receive/transmit terminal and a GND terminal. The switch unit switches the coupling destination of a second terminal in a second filter between the terminals. In the second filter, the second terminal is a common terminal coupled to a terminal, which is to be at the reference potential, of a first filter. When a first terminal of the first filter is to be coupled to the receive/transmit terminal terminal, the switch unit switches the coupling destination of the second terminal to the ground terminal.