A method for blackening at least one wafer includes: (a) performing a reduction treatment on the at least one wafer; and (b) illuminating the at least one wafer with an ultraviolet light. The at least one wafer after the illumination of the UV light has a blackening uniformity value (DE value) smaller than 0.6, and a chromatic value (L value) smaller than 54. In addition, a blackened wafer made from the method is also provided.

An acoustic wave device includes a material layer which has Euler angles and an elastic constant at the Euler angles, a piezoelectric body which includes first and second principal surfaces opposing each other, is laminated directly or indirectly on the material layer so that the second principal surface is on the material layer side and has Euler angles, and whose elastic constant at the Euler angles, and an IDT electrode which is disposed on at least one of the first principal surface and the second principal surface of the piezoelectric body. At least one elastic constant among elastic constants C.sub.11 to C.sub.66 of the material layer not equal to 0 and at least one elastic constant among elastic constants C.sub.11 to C.sub.66 of the piezoelectric body not equal to 0 have opposite signs to each other.

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 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 elastic wave apparatus includes a piezoelectric substrate including a main surface and a polarization axis direction having a tilt angle with respect to the main surface, an IDT electrode provided on the main surface, and at least one line on the main surface and between an end edge of the main surface and the IDT electrode. A relationship a≦316|cos(θ)|μm is satisfied where a denotes a distance from the end edge of the main surface to the IDT electrode and b≧28 μm where a dimension of the line along a direction connecting the end edge to the IDT electrode is defined as a width, b denotes the width of the line when one line is provided, and b denotes the sum of the widths of multiple lines when the multiple lines are provided.

An acoustic wave device includes a support substrate, a piezoelectric layer provided on the support substrate, at least a pair of comb-shaped electrodes provided on the piezoelectric layer, each of the comb-shaped electrodes including a plurality of electrode fingers, and an insulating layer provided between the support substrate and the piezoelectric layer, the insulating layer having, in at least a part thereof, a plurality of void regions of which extending directions are different from each other when viewed from a thickness direction of the support substrate, a width in the corresponding extending direction of each of the void regions being longer than a width in a direction orthogonal to the corresponding extending direction when viewed from the thickness direction of the support substrate.

An acoustic wave device includes a piezoelectric body portion, an interdigital transducer electrode connected to a first terminal and a second terminal, and a reflector connected to the second terminal. In the interdigital transducer electrode, in the interdigital transducer electrode, where, of a group of electrode fingers, the electrode finger located at one end in a second direction is a first end electrode finger and the electrode finger located at another end is a second end electrode finger, the first end electrode finger is located between the reflector and the second end electrode finger in the second direction. An outer busbar portion of one of a first busbar and a second busbar, not connected to the first end electrode finger, is located on an inner side in the second direction relative to a center portion, in a first direction, of the first end electrode finger.

A micro-transfer printable transverse bulk acoustic wave filter comprises a piezoelectric filter element having a top side, a bottom side, a left side, and a right side disposed over a sacrificial portion on a source substrate. A top electrode is in contact with the top side and a bottom electrode is in contact with the bottom side. A left acoustic mirror is in contact with the left side and a right acoustic mirror is in contact with the right side. The thickness of the transverse bulk acoustic wave filter is substantially less than its length or width and its length can be greater than its width. The transverse bulk acoustic wave filter can be disposed on, and electrically connected to, a semiconductor substrate comprising an electronic circuit to control the transverse bulk acoustic wave filter and form a composite heterogeneous device that can be micro-transfer printed.

In an acoustic wave device, a piezoelectric body is directly or indirectly laminated on a silicon support substrate, and a functional electrode is provided on the piezoelectric body. A support layer is directly or indirectly laminated on the silicon support substrate, and the support layer is located outside the functional electrode when viewed in plan view. A silicon cover layer is provided on the support layer that includes an insulating material, and a space A is defined by the silicon support substrate, the support layer, and the silicon cover layer. The electric resistance of the silicon support substrate is higher than the electric resistance of the silicon cover layer.

An acoustic wave device includes a support substrate having a thickness in a first direction, a piezoelectric layer on the support substrate, an interdigital transducer electrode on the piezoelectric layer and including first and second electrode fingers, the first electrode fingers extending in a second direction crossing the first direction, the second electrode fingers extending in the second direction and facing the first electrode fingers in a third direction orthogonal or substantially orthogonal to the second direction, and a reinforcing film on the piezoelectric layer. The support substrate and the piezoelectric layer include a hollow therebetween at a position overlapping the interdigital transducer electrode in the first direction. At least one through hole penetrates the piezoelectric layer at a position not overlapping the interdigital transducer electrode in the first direction, and the through hole communicates with the hollow. The reinforcing film overlaps the hollow in the first direction.