Patent ID: 8803402

Claim:
An elastic wave device comprising: a piezoelectric substrate having a reciprocal velocity plane which is concave in a propagating direction in which an elastic wave propagates; and an elastic wave resonator including a comb-shaped electrode pair which includes a first comb-shaped electrode and a second comb-shaped electrode both provided on the piezoelectric substrate, the first comb-shaped electrode and the second comb-shaped electrode interdigitating with each other, comb-shaped electrode pair being configured to trap energy of the elastic wave therein, wherein the first comb-shaped electrode includes a first common electrode and a plurality of first interdigital electrode fingers connected to the first common electrode, wherein the second comb-shaped electrode includes a second common electrode and a plurality of second interdigital electrode fingers connected to the second common electrode, the plurality of second interdigital electrode fingers interdigitaing with the plurality of first interdigital electrode fingers, and wherein the elastic wave resonator has: a first region in which the plurality of first interdigital electrode fingers interdigitate with the plurality of second interdigital electrode fingers, and a pitch of the first interdigital electrode fingers and the second interdigital electrode fingers is constant along a direction perpendicular to the propagating direction, a second region provided between the first region and the first common electrode, and a pitch of the first interdigital electrode fingers and the second interdigital electrode fingers in the second region is wider than the pitch in the first region, and a third region provided between the first region and the second common electrode, and a pitch of the first interdigital electrode fingers and the second interdigital electrode fingers in the third region is wider than the pitch in the first region.