Piezoelectric device and liquid discharge head

A piezoelectric device comprising:

• a diaphragm that is coupled to a first substrate and partitions a part of a space together with the first substrate;
• and
• a piezoelectric element in which a lower electrode, a piezoelectric layer, and an upper electrode are stacked in this order along a stacking direction on a side opposite to the space of the diaphragm, wherein
• the diaphragm vibrates in response to driving of the piezoelectric element,
• when a region in which the space and the diaphragm overlap when viewed in the stacking direction is defined as a flexible region in a width direction intersecting the stacking direction, the flexible region includes an active region in which the diaphragm, the lower electrode, the piezoelectric layer, and the upper electrode overlap when viewed in the stacking direction, and
• an inflection point of deflection of the diaphragm in a state of being most deflected toward the space when the piezoelectric element is driven is located in a portion of the flexible region other than the active region in the width direction.