Acoustic wave element

An acoustic wave element comprising:

• an IDT electrode comprising a plurality of electrode fingers and exciting a surface acoustic wave,
• a first substrate on an upper surface of which the IDT electrode is located, which has a thickness of less than a wavelength λ of the surface acoustic wave defined by 2 times a repetition interval of the plurality of electrode fingers and is configured by a piezoelectric crystal,
• a second substrate bonded to a lower surface of the first substrate, and configured by an Si single crystal having a plane orientation of a (100) plane or (110) plane or a plane equal to them, in which substrate a crystal axis of the Si single crystal parallel to the upper surface of the first substrate is inclined at any angle of 25° to 65°, 115° to 155°, 205° to 245°, and 295° to 345° relative to a direction of propagation of the acoustic wave when viewed from the upper surface of the superposed first substrate.