BULK WAVE RESONATOR AND BANDWIDTH PASSING FILTER

To suppress a spurious of a bulk wave.SOLUTION: A bulk wave resonator is a bulk wave resonator using a bulk wave, and comprises: a support substrate; an acoustic reflection in which a plurality of kinds of dielectric bodies having a different acoustic impedance is laminated on the support substrate; a piezoelectric layer laminated on the acoustic reflection film; a first electrode and a second electrode, that are oppositely arranged onto a first surface that is a surface on the side opposite to the acoustic reflection film in the piezoelectric layer with an interval, and to which a voltage for generating the bulk wave to the piezoelectric layer is applied; and an acoustic material that is arranged onto the outer side of the first direction of the electrode area where a first electrode and a second electrode are arranged on the first surface of the piezoelectric layer when a direction where the first and second electrodes are faced of a direction parallel to the first surface of the piezoelectric layer is a first direction. The electrode is not arranged on a second surface that is a surface on the acoustic reflection film in the piezoelectric layer.SELECTED DRAWING: Figure 34 【課題】バルク波のスプリアスを抑制する。【解決手段】バルク波共振子は、バルク波を用いたバルク波共振子であって、支持基板と、音響インピーダンスが異なる複数種類の誘電体が前記支持基板上に積層された音響反射膜と、前記音響反射膜上に積層された圧電層と、前記圧電層における前記音響反射膜とは反対側の面である第１面上に間隔を空けて対向配置され、前記バルク波を前記圧電層に発生させる電圧が印加される第１電極および第２電極と、前記圧電層の前記第１面に対して平行な方向のうち、前記第１電極と前記第２電極とが対向する方向を第１方向としたとき、前記圧電層の前記第１面上において、前記第１電極および前記第２電極が配置される電極エリアの前記第１方向の外側に配置される吸音材と、を備え、前記圧電層における前記音響反射膜側の面である第２面には電極が配置されていない。【選択図】図３４