Acoustic wave element and method for manufacturing same

An acoustic wave element comprising:

• a piezoelectric substrate;
• interdigital transducers provided on a first surface of the piezoelectric substrate;
• and
• a dielectric film provided on the interdigital transducers,
• wherein the piezoelectric substrate is a −10° to 75° rotated Y-cut X-propagation LiNbO3 substrate, a 120° to 170° rotated Y-cut X-propagation LiNbO3 substrate, a Y-Z LiNbO3 substrate, an X-cut 35° to 45° Y-propagation LiNbO3 substrate, an X-cut 160° to 175° Y-propagation LiNbO3 substrate, an LiNbO3 substrate, a −10° to 60° rotated Y-cut X-propagation LiTaO3 substrate, an X-cut 35° to 45° Y-propagation LiTaO3 substrate, an LiTaO3 substrate, a langasite substrate, a quartz substrate, a ZnO substrate, a piezoelectric ceramics substrate, an AN thin film substrate, a ZnO thin film substrate, a piezoelectric ceramics thin film substrate, or a ScAlN thin film substrate,
• in the dielectric film, an acoustic velocity of a propagating transverse wave is ⅔ times or less of an acoustic velocity of a slow transverse wave propagating through the piezoelectric substrate, and a surface acoustic wave velocity is 1010 m/s or more and
• the dielectric film includes a (Bi2O3)x(SiO2 or GeO2)(1-x) film wherein X is 0.3 to 1.0, a compound film including Bi, a BSO film, a BGO film, an In2O3 film, or a compound film including In.