Patent ID: 7221075

Claim:
A piezoelectric/electrostrictive sensor device comprising: a ceramic substrate having a thick portion, a thin diaphragm portion mounted integrally on an end surface of the thick portion, and a cavity formed by the thick portion and the thin diaphragm portion to communicate with the outside; and a piezoelectric/electrostrictive element having a layered structure fixed to an outer surface of the thin diaphragm portion of the ceramic substrate and including a lower electrode, a piezoelectric/electrostrictive film, and an upper electrode, the thin diaphragm portion of the ceramic substrate being vibrated in conjunction with driving of the piezoelectric/electrostrictive element, wherein shape and dimension relations defined in the following (A) to (C) are satisfied; (A) a shape of the thin diaphragm portion is an outward protruding arch shape, and an outward protrusion height of the arch shape is in a range of 5 to 50 μm; (B) a mounting width of the thin diaphragm portion is in a range of 600 to 2000 μm; and (C) a ratio (height/width) of the height to the width of the thick portion is in a range of 0.25 to 3, wherein the piezoe/ectric/electrostrictive element senses vibration of the thin diaphragm portion and at least the dimension relation of the thick portion is selected to reduce unwanted damping of the thin diaphragm portion.