Patent ID: 8669832

Claim:
An acoustic wave device comprising: a piezoelectric substrate having a surface; a first interdigital transducer (IDT) electrode including a first comb-shaped electrode formed on the surface of the piezoelectric substrate, and a second comb-shaped electrode formed on the surface of the piezoelectric substrate, the second comb-shaped electrode facing the first comb-shaped electrode; and a first separate electrode formed on the surface of the piezoelectric substrate, wherein the first IDT electrode and the first separate electrode are arranged in a first direction, the first comb-shaped electrode includes: a first bus bar extending in the first direction; a plurality of first interdigitated electrode fingers extending from the first bus bar toward the second comb-shaped electrode in a second direction different from the first direction; and a plurality of first dummy electrode fingers extending from the first bus bar toward the second comb-shaped electrode in the second direction, the second comb-shaped electrode includes: a second bus bar extending in the first direction; a plurality of second interdigitated electrode fingers extending from the second bus bar toward the first comb-shaped electrode in a third direction opposite to the second direction, the second interdigitated electrode fingers being interdigitated with the first interdigitated electrode fingers in an interdigitated region, the second interdigitated electrode fingers facing the first dummy electrode fingers in the third direction; a plurality of second dummy electrode fingers extending from the second bus bar toward the first comb-shaped electrode in the third direction, the second dummy electrode fingers facing the first interdigitated electrode fingers in the third direction; a plurality of weighted parts having electrodes at spaces between the second interdigitated electrode fingers and the second dummy electrode fingers, the weighted parts being formed in a non-interdigitated region outside the interdigitated region; and a non-weighted part having no electrode at a space out of the spaces which is closest to the separate electrode, the non-weighted part being disposed in the non-interdigitated region, wherein the weighted parts have widths gradually increasing from a center of the first bus bar to both ends of the first bus bar in the second direction.