Patent ID: 8598968

Claim:
An elastic wave device comprising: a piezoelectric substrate; an IDT electrode disposed on the piezoelectric substrate; a first dielectric layer disposed on the piezoelectric substrate, the first dielectric layer covering the IDT electrode and being made of a medium with a frequency-temperature characteristic opposite to that of the piezoelectric substrate; and a second dielectric layer disposed on the first dielectric layer, the second dielectric layer being made of a medium that propagates a transverse wave faster than a speed of a transverse wave propagating on the first dielectric layer; wherein the first dielectric layer has a convex portion on a top face of the first dielectric layer, the convex portion being provided over the IDT electrode; and wherein a relation of one of 0 <t 1≦0.28λ and 0 <t 2≦1.5 h , and 0.28 <t 1≦0.3λ and 0 <t 2≦0.58 h is satisfied, where t 1 is a height from a boundary face between the piezoelectric substrate and the first dielectric layer to a bottom end of the convex portion, t 2 is a height from a top end of the convex portion to the bottom end of the convex portion, h is a film thickness of the IDT electrode, and λ is a wavelength of a major wave excited by the IDT electrode.