An acoustic wave device includes an IDT electrode provided on a piezoelectric substrate. The IDT electrode includes a crossing area including a central area, and first and second low-acoustic-velocity areas on both sides in a direction perpendicular or substantially perpendicular to an acoustic wave propagating direction. First and second high-acoustic-velocity areas are provided outside the first and second low-acoustic-velocity areas. Mass adding films are laminated in respective portions of first and second electrode fingers, the respective portions being positioned in the first and second low-acoustic-velocity areas. In at least one of the mass adding films, a width of a first end portion and a width of a second end portion are narrower than a width of a central portion, and a protruding portion protrudes from at least one of the first and second end portions.

An elastic wave device includes a piezoelectric substrate including an IDT electrode provided on one main surface. In the elastic wave device, a center region positioned in a central portion in a direction perpendicular to an elastic wave propagation direction, first and second low acoustic velocity regions positioned outside of the center region, and first and second high acoustic velocity regions positioned outside of the first and the second low acoustic velocity regions in plan view are provided. A groove portion overlaps with one of the first electrode finger and the second electrode finger in plan view in a portion located in the first and second low acoustic velocity regions on the main surface. An acoustic velocity adjusting layer is provided in the groove portion.

An acoustic wave device utilizes Love waves and includes a piezoelectric substrate (piezoelectric body), an IDT electrode provided on the piezoelectric substrate, and a first dielectric film that is provided on the piezoelectric substrate and covers the IDT electrode. A center region, first and second edge regions, and first and second gap regions are disposed in this order in the IDT electrode. A mass-adding film is provided inside the first dielectric film in the first edge region and the second edge region. When T1 is the film thickness of the portion of the first dielectric film located between the IDT electrode and the mass-adding film and T2 is the film thickness of the portion of the first dielectric film located between the mass-adding film and the surface of the first dielectric film on the opposite side from the piezoelectric substrate, T1/(T1+T2)<about 0.5.

An acoustic wave device includes a plurality of interdigital transducer electrodes, in a first interdigital transducer electrode, a first electrode finger includes a wide portion having a greater width in the second direction than a center portion. In the first interdigital transducer electrode, for the first electrode finger, a first distance that is a maximum distance in the second direction between a center line of the center portion in a first direction is shorter than a second distance that is a maximum distance in a second direction between the center line of the center portion and an outer edge, away from a second interdigital transducer electrode, of the wide portion.

An acoustic wave device includes an interdigital transducer electrode connected to first and second terminals, and a reflector connected to the second terminal. In a group of electrode fingers of the interdigital transducer electrode, the electrode fingers at one end and another end in a second direction are respectively first and second end electrode fingers, the first end electrode finger includes a wide portion at a distal end portion. The first end electrode finger is located between the reflector and the second end electrode finger in the second direction. An inner busbar portion of one of first and second busbars not connected to the first end electrode finger, is located on an inner side in the second direction relative to the wide portion of the first end electrode finger so as not to overlap the wide portion of the first end electrode finger in a first direction.

An elastic wave device includes an IDT electrode provided on a piezoelectric substrate and including a first end region including one end of the IDT electrode in an elastic wave propagation direction, a second end region including the other end of the IDT electrode in the elastic wave propagation direction, and an inner region that is located farther toward an inside than the first and second end regions in the elastic wave propagation direction, includes first and second high-acoustic-velocity regions, and a center region and first and second low-acoustic-velocity regions, located in the crossing region. The mass of the IDT electrode in the crossing region in the first and second end regions is smaller than the mass of the IDT electrode in the crossing region in the inner region.

An acoustic wave filter device includes a piezoelectric layer, a high-acoustic-velocity member, a low-acoustic-velocity film between the high-acoustic-velocity member and the piezoelectric layer, and first and second IDT electrodes on the piezoelectric layer to define acoustic wave resonators. An acoustic wave resonator of a series-arm resonator portion closest to an antenna end and/or an acoustic wave resonator of a parallel-arm resonator portion closest to the antenna end includes the first IDT electrode including first and second electrode fingers, and the remaining acoustic wave resonators include the second IDT electrode including third and fourth electrode fingers. In the first IDT electrode, a central area, first and second low-acoustic-velocity areas, and first and second high-acoustic-velocity areas extend along a direction perpendicular or substantially perpendicular to an acoustic wave propagating direction. First and second envelopes connecting the tips of the third and fourth electrode fingers of the second IDT electrode are inclined.

An acoustic wave device includes a piezoelectric substrate with a reverse-velocity surface having an ellipse shape, an IDT electrode on the piezoelectric substrate, and a dielectric film on the piezoelectric substrate and covering the IDT electrode. The acoustic wave device utilizes a Love wave. The IDT electrode includes an intersecting region in which first electrode fingers and second electrode fingers are interdigitated. The intersecting region includes a central region, a first edge region and a second edge region located at both ends of the central region. When x(%) denotes a wavelength-normalized film thickness of the IDT electrode and y (g/cm.sup.3) denotes an electrode density of the IDT electrode, the wavelength-normalized film x is set at a value not less than x that satisfies Equation 1. The film thicknesses of the dielectric films in the first and second edge regions are smaller than the dielectric film in the central region.

An elastic wave device includes a piezoelectric substrate and an interdigital transducer (IDT) electrode. The IDT electrode is disposed on the piezoelectric substrate and includes an electrode layer including molybdenum as a main component. The duty ratio of the IDT electrode is about 0.3 to about 0.48.

An electro acoustic resonator is provided. The resonator has a gap short structure (GSS) to electrically short at least an area of the transversal gap to suppress transversal gap mode excitations. The gap short structure may be provided by a conductive stripe in the gap and parallel to or inclined with respect to the bus bar (BB) shorting adjacent IDT fingers. Additional connectors between the stripe and the bus bar may be provided. The connectors may have different pitch or metallization ratio with respect to the ID fingers. The connectors may be offset from the position of the fingers and my be inclined with respect to the bus bars. Multiple parallel stripes in the gap may provide a transversal reflector. By using a gap short structure a further improved transversal mode suppression of piston mode designs can be achieved.