Patent ID: 7719390

Claim:
A dual mode piezoelectric filter comprising: a piezoelectric material layer composed of a piezoelectric thin film of the high-cut type formed on a substrate, a first electrode and a second electrode formed on one of the major surfaces of the piezoelectric material layer with a gap provided therebetween, and a third electrode formed on the other major surface of the piezoelectric material layer opposite to the first electrode, the second electrode, and the gap, wherein an interelectrode mass load element further is formed in the gap or at a position opposite to the gap on a surface of the piezoelectric material layer, and the relationships (ρ 1 ×h 1 )≦(ρa×ha) and (ρ 2 ×h 2 )≦(ρa×ha) are satisfied, where ρ 1 is the density and h 1 is the thickness of the first electrode, ρ 2 is the density and h 2 is the thickness of the second electrode, and ρa is the density and ha is the thickness of the interelectrode mass load element.