Patent ID: 8354896

Claim:
A ladder filter, comprising a plurality of acoustic wave devices, at least two of the plurality of acoustic wave devices each including, a substrate made of a piezoelectric material, a pair of interdigital electrodes formed on the substrate, each of the interdigital electrodes including a plurality of electrode fingers, and an adjustment medium including at least a single layer and formed on at least a part of the pair of the interdigital electrodes, the adjustment medium including at least one thick portion and a thin portion, the thin portion being null or thinner than the thick portion, the at least one thick portion and the thin portion both being formed on the pair of the interdigital electrodes, a total area of the at least one thick portion in a region covering the pair of interdigital electrodes being determined according to a predetermined characteristic value, wherein said at least two of the plurality of acoustic wave devices include at least two acoustic wave devices that differ from each other with respect to the size of the total area of the at least one thick portion of the adjustment medium.