Patent ID: 8222973

Claim:
An elastic wave resonator comprising: a piezoelectric substrate; and an IDT electrode located on the piezoelectric substrate; wherein the IDT electrode includes: first and second common electrodes arranged so as to be separated from each other on the piezoelectric substrate; a plurality of first electrode fingers each including a first end connected to the first common electrode and a second end extending toward the second common electrode; a plurality of second electrode fingers each including a first end connected to the second common electrode and a second end thereof extending toward the first common electrode; a plurality of first dummy electrode fingers each including a first end connected to the second common electrode, and a second end extending toward the first common electrode and being arranged with a gap interposed between itself and the second end of one of the plurality of first electrode fingers; a plurality of second dummy electrode fingers each including a first end being connected to the first common electrode, and a second end extending toward the second common electrode and being arranged with a gap interposed between itself and the second end of one of the plurality of second electrode fingers; wherein a crossing region is defined by a portion in which the first and second electrode fingers overlap one another in an elastic wave propagation direction, and a portion in which the first and second dummy electrode fingers are located is a non-crossing region; the IDT electrode is apodization weighted so that a crossing width of the first and second electrode fingers changes in the elastic wave propagation direction, there being at least two points of change in the apodization weighting at which the crossing width changes from increasing to decreasing; and a metallization ratio that is a ratio of an area of electrode portions including the first and second electrode fingers or the first and second dummy electrode fingers to an entire area of a region in which the electrode portions are provided, is relatively high in at least a portion of the non-crossing region compared with that in the crossing region; and compared with a metallization ratio of a non-crossing region located between the at least two points of change, a metallization ratio of a non-crossing region located between a first end of the IDT electrode in the elastic wave propagation direction and a point of change closest to a side of the first end of the IDT electrode, and a metallization ratio of a non-crossing region located between a second end of the IDT electrode in the elastic wave propagation direction and the point of change closest to a side of the second end, are relatively high.