To provide a piezoelectric sound wave sensor more improved in sensing sensitivity than heretofore.
It is considered that parts of a lower electrode 3, a piezoelectric film 4, an upper electrode 5, and an oxide film 6 existing on the surface of a diaphragm part 1 give the effect of the residual stress on the bent of the diaphragm part 1 and parts of the lower electrode 3, the piezoelectric film 4, the upper electrode 5, and the oxide film 6 give less effect thereon. Thus, provision of the upper electrode 5 and the piezoelectric film 4 on the surface of the diaphragm part 1 within a range narrower than the diaphragm part 1 reduces the effect of the residual stress of the upper electrode 5 and the piezoelectric film 4 given onto the diaphragm part 1 in comparison with prior arts wherein the upper electrode 5 and the piezoelectric film 4 are provided to the same area as that of the diaphragm part 1 or to an area broader than the diaphragm part 1 so that the diaphragm part 1 can easily be bent, resulting in that the sensing sensitivity of the piezoelectric sound wave sensor can be enhanced more than that of prior arts.
RI SHIYOUBOKU
KAWADA HIROSHI
SI-BEI XIONG
MATSUSHIMA CHOMEI
PROASSIST KK
MATSUSHITA ELECTRIC WORKS LTD
Atsuo Mori