Patent ID: 7786649
Filing Date: 2010-08-31
Classification: H03H

Abstract:
1. A filter comprising: series-arm resonators and parallel-arm resonators having a substrate, a lower electrode supported by the substrate, a piezoelectric film provided on the lower electrode and an upper electrode provided on the piezoelectric film, the filter being a ladder type filter, each of multiple resonators among the series-arm resonators and parallel-arm resonators having a portion in which the upper electrode overlaps the lower electrode across the piezoelectric film, said portion having an elliptical shape, an axial ratio of said portion of one of the series-arm resonators being different from axial ratios of portions of at least one of the other resonators among the series-arm resonators, an area of the portion of said one of the series-arm resonators being the same as that of the portion of said at least one of the other resonators among the series-arm resonators.