| 摘要 |
PROBLEM TO BE SOLVED: To provide a bulk acoustic wave (BAW) resonator capable of avoiding the mismatch between an active region and an external region and capable of providing a smooth transition of propagating waves in the active region to evanescent waves in the external region.SOLUTION: A BAW resonator 100 includes: an internal region (active region) 104, a border region 108, and an external region 112; a piezoelectric layer 116 disposed in the internal region, the border region, and the external region; a first electrode (upper electrode) 128 disposed in the internal region and the border region and coupled with a first surface 120 of the piezoelectric layer; an extension 128' disposed in the external region, coupled with the first surface of the piezoelectric layer and having an acoustic impedance that is at least similar to an acoustic impedance of the first electrode; and a second electrode (bottom electrode) 132 coupled with a second surface 124 of the piezoelectric layer, the second surface being opposite the first surface 120. |
