PROBLEM TO BE SOLVED: To provide a technique capable of improving the reception sensitivity of a piezoelectric element in a manner different from using a thinner diaphragm.SOLUTION: The piezoelectric element includes: a piezoelectric body and a diaphragm 63 using, as a vibration material, an anisotropic single crystal silicon 7 which has an azimuth in which the Poissons ratio is higher and an azimuth in which the Poissons ratio is lower (referred to as azimuth with low Poissons ratio). The piezoelectric body and the diaphragm are laminated so that the azimuth with low Poissons ratio is aligned with a direction along a high expansion and contraction direction where the degree of relative expansion and contraction generated depending on the support structure of the piezoelectric body is high (referred to as high expansion and contraction direction) not in a direction where the degree of relative expansion and contraction is low.SELECTED DRAWING: Figure 8COPYRIGHT: (C)2017,JPO&INPIT【課題】振動板の薄化とは異なる圧電素子の受信感度を向上させる新たな技術を提供する。【解決手段】圧電素子は、圧電体と、相対的にポアソン比が高い方位と低い方位(以下「低ポアソン比方位」という)とを有する異方性の単結晶シリコン7を振動用素材とする振動板63と、を備え、低ポアソン比方位が、圧電体の支持構造に応じて生じる相対的に伸縮する程度の高い方向(以下「高伸縮方向」という)と低い方向とのうちの高伸縮方向に沿った方向となるように圧電体と振動板とが積層される。【選択図】図8
