Patent ID: 7602101
Filing Date: 2009-10-13
Classification: H03H

Abstract:
1. A piezoelectric thin-film resonator comprising: a lower electrode supported by a substrate, a space being defined below the lower electrode; a piezoelectric film provided on the lower electrode and the substrate; and an upper electrode provided on the piezoelectric film so as to form a resonance portion in which the upper electrode faces the lower electrode across the piezoelectric film, at least one of the lower electrode and the upper electrode having an interconnection portion used to extract a signal from the resonance portion and located above the space, said at least one of the lower electrode and the upper electrode having a first mass per unit area in which said at least one of the lower electrode and the upper electrode contacts the piezoelectric film and a second mass per unit area in the resonance portion, the first mass per unit are being smaller than the second mass per unit area, wherein said at least one of the lower electrode and the upper electrode has a first density in the interconnection portion and a second density in the resonance portion, the first density that is smaller than the second density.