Patent ID: 8427032

Claim:
A surface acoustic wave device comprising: a piezoelectric substrate; an IDT electrode disposed on the piezoelectric substrate; a first insulating film disposed so as to cover an upper surface of the IDT electrode on the piezoelectric substrate; and at least one second insulating film disposed on the first insulating film; wherein the piezoelectric substrate, the IDT electrode, the first insulating film, and the at least one second insulating film are arranged and configured to utilize a higher-order mode of an SH wave; an acoustic velocity of a surface acoustic wave in at least one insulating film located closer to the IDT electrode than an insulating film located at an outermost surface among the at least one second insulating film is higher than the acoustic velocity of a surface acoustic wave propagating in the insulating film located at the outermost surface among the at least one second insulating film; and the insulating film located at the outermost surface is made of silicon oxide, the thickness thereof is about 45% to about 85% of a wavelength of the surface acoustic wave, the insulating film or films other than the insulating film located at the outermost surface are made of at least one insulating material selected from the group consisting of silicon nitride, aluminum oxide, and silicon carbide, and the thickness thereof is about 5% to about 21% of the wavelength of the surface acoustic wave.