An acoustic wave device includes first and second piezoelectric layers and an IDT electrode. The second piezoelectric layer is located above the first piezoelectric layer in a first direction. The IDT electrode includes first and second busbar electrodes and first and second electrode fingers. The first and second busbar electrodes oppose each other. The first electrode finger is provided to the first busbar electrode and extends toward the second busbar electrode. The second electrode finger is provided to the second busbar electrode and extends toward the first busbar electrode. The first and second electrode fingers are sandwiched between the first and second piezoelectric layers in the first direction. The first and second electrode fingers extend in a second direction which intersects with the first direction and are located to overlap each other as seen in a third direction perpendicular or substantially perpendicular to the second direction.

A resonator element includes a substrate including a thin-wall part and a thick-wall part, and an electrode part including an excitation electrode, a pad electrode, and an extraction electrode, wherein the electrode part includes a first electrode layer arranged in the pad electrode placement area and the first area on the substrate, a second electrode layer which is arranged in an area overlapping the first electrode layer on the first electrode layer, and which is larger in thickness than the first electrode layer, a third electrode layer which is arranged throughout an area overlapping the pad electrode placement area and the first area in a plan view on the second electrode layer, and an area overlapping the second area and the excitation electrode placement area in a plan view on the substrate, and which is smaller in thickness than the second electrode layer, and a fourth electrode layer which is arranged in an area overlapping the third electrode layer on the third electrode layer, and which is smaller in thickness than the second electrode layer.

A piezoelectric resonator device according to one or more embodiments may include at least a core section. The core section includes: a three-ply structured crystal resonator in which a vibrating part is hermetically sealed; and a heater IC as a heating element. At least whole of a second main surface of a second sealing member of the crystal resonator is thermally coupled to the heater IC.

Provided is an acoustic resonator including: a substrate including a first cavity; a first electrode formed above the substrate; a piezoelectric layer formed on one surface of the first electrode; and a second electrode formed on one surface of the piezoelectric layer, wherein the first electrode and the piezoelectric layer include an overlapping area that corresponds to a first end and a second end of the first cavity, the first electrode has a termination surface formed as an inclined surface of a first acute angle .sub.1 outside the overlapping area with respect to the second end of the first cavity, the piezoelectric layer is formed to include a first air bridge area that has a second cavity and is formed between the piezoelectric layer and the first electrode in a vertical direction and between the second end of the first cavity and the termination surface in a horizontal direction.

A piezoelectric resonator device having a sandwich structure is provided, which can be easily adapted to reduction in size. A crystal oscillator 101 includes: a crystal resonator plate 2; a first sealing member 3 covering a first excitation electrode 221 of the crystal resonator plate 2; and a second sealing member 4 covering a second excitation electrode 222 of the crystal resonator plate 2. A substantially rectangular parallelepiped shaped package 12 is formed by bonding: the first sealing member 3 to the crystal resonator plate 2; and the second sealing member 4 to the crystal resonator plate 2. The package 12 includes an internal space 13 in which is hermetically sealed a vibrating part 23 of the crystal resonator plate 2 including the first excitation electrode 221 and the second excitation electrode 222. A bowling material 11 hermetically sealing the vibrating part 23 of the crystal resonator plate 2 is formed to have an annular shape in plan view, and is disposed along an outer peripheral edge of the package 12 excluding four corners thereof.

Method of forming a termination angle in a titanium tungsten layer include providing a titanium tungsten layer and applying a photo resist material to the titanium tungsten layer. The photo resist material is exposed under a defocus condition to generate a resist mask, wherein an edge of the exposed photo resist material corresponds to the sloped termination. The titanium tungsten layer is etched with an etching material, wherein the etching material at least partially etches the photo resist material exposed under the defocused condition, and wherein the etching results in the sloped termination in the titanium tungsten layer.

A filter device includes a longitudinally coupled resonator elastic wave filter that includes IDT electrodes including low acoustic velocity regions in outer side portions of center regions of the IDT electrodes and high acoustic velocity regions in outer side portions of the low acoustic velocity regions in a direction orthogonal or substantially orthogonal to an elastic wave propagation direction, and defines and functions as a first bandpass filter, and elastic wave resonators that are electrically connected to the longitudinally coupled resonator elastic wave filter.

A piezoelectric element body has a first principal surface and a second principal surface. A pair of first electrodes is disposed on the first principal surface. The vibrating body includes a metal plate, an insulating layer, and a pair of second electrodes. The metal plate has a third principal surface and a fourth principal surface. The insulating layer is disposed on the third principal surface. The pair of second electrodes is disposed on the insulating layer. The piezoelectric element and the vibrating body are disposed in such a manner that the first principal surface and the third principal surface oppose each other via the insulating layer. The pair of second electrodes physically contacts the respective first electrodes. The second electrodes are exposed from the piezoelectric element and are separated from all of edges of the insulating layer, when viewed from a direction orthogonal to the third principal surface.

A resonance device is provided having a resonator with opposing upper and lower lids. The resonator includes a base, and multiple vibration arms that are connected to a front end of the base so as to extend away from the base. Moreover, a frame surrounds a periphery of the base portion and the vibration arms and one or more holding arms connect the base to the frame. The base, the vibration arms, and the holding arm include a substrate and a temperature characteristics correction layer laminated on the substrate and having a material with a coefficient of thermal expansion different from that of the substrate. The base, the vibration arms, and the holding arm are formed integrally with the substrate and the temperature characteristics correction layer.

A transducer includes first and second piezoelectric layers made of corresponding different first and second piezoelectric materials and three or more electrodes, implemented in two or more conductive electrode layers. The first piezoelectric layer is sandwiched between a first pair of electrodes and the second piezoelectric layer is sandwiched between a second pair of electrodes. The first and second pairs of electrodes contain no more than one electrode that is common to both pairs.