In a bulk acoustic wave (BAW) filter based on laterally acoustically coupled resonators on piezoelectric thin films, one can utilize two distinct acoustic plate wave modes of different nature, for example the thickness extensional (longitudinal) TE1 and the second harmonic thickness shear (TS2) mode to form a bandpass response. The invention is based on the excitation of at least two lateral standing wave resonances belonging to different plate wave modes that facilitate the transmission of signal. The passband is designed by tailoring the wave propagation characteristics in the device such that the resonances are excited at suitable frequencies to form a passband of a desired shape. The bandwidth of the filter described herein may therefore be more than twice that of the existing state-of-the-art microacoustic filters. Consequently, it has significant commercial and technological value.

A crystal oscillating wafer is a sheet in a symmetric shape. A symmetry axis of the crystal oscillating wafer has at least a first point and a second point. A distance between the first point and a first endpoint on the symmetry axis is less than a distance between the second point and the first endpoint. A width that is of the crystal oscillating wafer and that passes the first point in a first direction is greater than a width that is of the crystal oscillating wafer and that passes the second point in the first direction. The first direction is a direction perpendicular to the symmetry axis on a surface of the crystal oscillating wafer. The crystal oscillating wafer includes an oscillation region including a first concave region located on an upper surface and a second concave region located on a lower surface of the crystal oscillating wafer.

A vibration element includes a crystal blank, a pair of excitation electrodes, and pair of extraction electrodes. The crystal blank is an AT cut crystal blank including a mesa part and an outer circumferential part which is thinner than the mesa part and surrounds the mesa part. The pair of excitation electrodes is provided on the two major surfaces of the mesa part. The pair of extraction electrodes include pad parts which are provided at the end parts of the crystal blank in the longitudinal direction on one major surface of the outer circumferential part and are connected to the pair of excitation electrodes. The length in the longitudinal direction of the crystal blank is less than 1000 m. When the resonance frequency is F (MHz) and t=1670/F, the distance y (m) between each of the pad parts and the mesa part satisfies 0.048F+1.18<y/t<0.097F+0.36.

A piezoelectric device includes a piezoelectric vibrating piece and a container. The piezoelectric vibrating piece has a rectangular planar shape and has a portion of a first side secured to the container. The piezoelectric vibrating piece has a second side opposing the first side and includes a projecting portion that projects outward from the second side in at least one of proximity of both ends of the second side along the second side.

A vibrator device includes a vibration element including a vibration portion and a fixed portion, a supporting member to which the fixed portion is attached to support the vibration element, and a first substrate to which the supporting member is attached, the supporting member includes a attaching portion attached to the first substrate, and A1?A2 is satisfied in a case where an area of a rectangular region including the fixed portion is A1 and an area of a rectangular region including the attaching portion is A2 in a plan view seen from a thickness direction of the vibration element.

A resonator element includes: a substrate; and an electrode that includes a first conductive layer provided on a surface of the substrate, and a second conductive layer, provided on the opposite side to the first conductive layer on the substrate side, which is disposed within an outer edge of the first conductive layer when seen in a plan view from a direction perpendicular to the surface.

A bulk-acoustic wave resonator includes a substrate; a lower electrode formed on the substrate, and at least a portion of the lower electrode is formed on a cavity; a piezoelectric layer formed on the lower electrode; an upper electrode formed on the piezoelectric layer; a membrane layer formed below the lower electrode and forming the cavity together with the substrate; and a protruding portion formed on the membrane layer and further formed in the cavity in a direction that extends away from the membrane layer.

A crystal unit includes an AT-cut crystal element that has a planar shape in a rectangular shape and a part as a thick portion. The crystal element includes a first end portion, a first depressed portion, the thick portion, a second depressed portion, and a second end portion in an order from a side of one short side in viewing a cross section taken along a longitudinal direction near a center of the short side. The first depressed portion is a depressed portion disposed from the thick portion toward the first end portion side, depressed with a predetermined angle a and subsequently bulged, and connected to the first end portion. The second depressed portion is a depressed portion disposed from the thick portion toward the second end portion side, depressed with a predetermined angle b and subsequently bulged, and connected to the second end portion.

Bulk acoustic wave resonators having a phononic crystal acoustic mirror are disclosed. An example integrated circuit package includes a bulk acoustic wave (BAW) resonator including a phononic crystal acoustic mirror (PCAM), the PCAM including a first arrangement of a first plurality of members in a first region, and a second arrangement of a second plurality of members in a second region, the first arrangement different from the second arrangement.

A resonator element includes: a substrate; and an electrode that includes a first conductive layer provided on a surface of the substrate, and a second conductive layer, provided on the opposite side to the first conductive layer on the substrate side, which is disposed within an outer edge of the first conductive layer when seen in a plan view from a direction perpendicular to the surface.