Piezoelectric stack, method of manufacturing piezoelectric stack, and piezoelectric element

A piezoelectric element comprising:

• a substrate;
• an output-side bottom electrode film on the substrate;
• an output-side piezoelectric film, being an oxide film, on the output-side bottom electrode film;
• an output-side top electrode film on the output-side piezoelectric film;
• an input-side bottom electrode film on the substrate;
• an input-side piezoelectric film, being a nitride film, on the input-side bottom electrode film;
• an input-side top electrode film on the input-side piezoelectric film;
• and
• an ultrasonic output part and ultrasonic input part placed in such a manner as not overlapping each other when viewed from a top surface of the substrate,
• the output-side piezoelectric film is separated from the input-side piezoelectric film by a gap,
• the ultrasonic output part comprising a stacked part of the output-side bottom electrode film, the output-side piezoelectric film, and the output-side top electrode film,
• the ultrasonic input part comprising a stacked part of the input-side bottom electrode film, the input-side piezoelectric film, and the input-side top electrode film.