To balance suppression of spurious caused by a transverse mode with miniaturization of a ladder-type filter, in a ladder-type filter used in a cellular phone, a wireless LAN terminal or the like.
In order to solve the problem, in this ladder-type filter 7, elastic-wave resonators 9, 10 on a series arm and elastic-wave resonators 11, 12 on a parallel arm are formed in a ladder-like shape on a piezoelectric substrate 8. Each of the elastic-wave resonators 9-12 has an interdigital electrode including a plurality of electrode finger pairs formed by making electrode fingers extending from a first bus bar intersect with electrode fingers extending from a second bus bar. The interdigital electrode 11a included in the elastic-wave resonator 11 on the parallel arm is structured such that an electrode intersection width D between the electrode finger extending from the first bus bar and the electrode finger extending from the second bus bar is 23 times or more of the wavelength of elastic waves excited by the interdigital electrode 11.
TSURUNARI TETSUYA
NAKAMURA HIROYUKI
Daisuke Nagano
Kentaro Fujii