Patent ID: 8035460

Claim:
A surface acoustic wave device, comprising: a substrate including lithium niobate; an IDT being provided on an upper surface of the substrate and including a plurality of electrode fingers; and a protective film covering the IDT and having an uneven shape on an upper surface thereof, wherein following relations are satisfied, p 1 +p 2 =p , and 7.8%≦ h /(2 ×p )≦9.8%, when a pitch width of one pitch of the IDT is p, a width of one of the electrode fingers is p 1 , a width between the electrode fingers is p 2 , and a thickness from the surface of the substrate to an upper part of the IDT in an equivalent thickness of aluminum is h, wherein following relations are satisfied, L 1 +L 2 =L, L 1 ≦p 1, and L 2 ≧p 2 wherein when a pitch width of one pitch in the uneven shape is L, a width of one pitch of a convex portion in the uneven shape is L 1 , and a width of one pitch of a concave portion in the uneven shape is L 2 , and wherein the electrode finger is made of any one of aluminum and an alloy including aluminum as a main component.