Ube Industries, Inc.

Eiji Masui

Keigo Nagao

Tetsuo Yamada

Kosuke Nishimura

Chisen Hashimoto

Hirofumi Kimura

A piezoelectric thin film resonator has a substrate and a piezoelectric layered structure including a lower electrode, piezoelectric aluminum nitride thin film with c-axis orientation and upper electrode formed on the substrate in this order. The lower electrode are made of a metal thin film including a layer containing ruthenium as a major component having a full-width half maximum (FWHM) of a rocking curve of a (0002) diffraction peak of ruthenium of 3.0&#xb0; or less. The piezoelectric aluminum nitride thin film formed on the lower electrode has a full-width half maximum (FWHM) of a rocking curve of a (0002) diffraction peak of 2.0&#xb0; or less.

Aluminum nitride thin film, composite film containing the same and piezoelectric thin film resonator using the same

A transmission band filter () having a series of elements () each composed of a film bulk acoustic resonator and grounded shunt elements () each composed of a film bulk acoustic resonator is connected between a transmission port () and an antenna port (). A reception band filter () having a series of elements () each composed of a film bulk acoustic resonator and grounded shunt elements () each composed of a film bulk acoustic resonator is connected between a reception port () and the antenna port (). A film bulk acoustic resonator () for adjustment is connected between the antenna port () and the ground. The resonance frequency of the adjusting film bulk acoustic resonator () lies between the upper limit frequency of the transmission frequency pass band of the transmission band filter () and the lower limit frequency of the reception frequency pass band of the reception band filter (). Therefore a duplexer such that it can be a monolithic element, the power handling capability is good, the size is small, and the cost is low is provided.

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Ube, Japan

Eiji Masui