[Object]
Providing a mechanism which can eliminate an influence of residual strain in a piezoelectric thin film, having excellent piezoelectric strain characteristics.
[Means of Solution]
No or few foreign substances exist or an abundance of foreign substances is low at grain boundaries, which are boundaries between crystal grains of the piezoelectric thin film, even after performing polarization processing (poling) on the piezoelectric thin film component. The width of the grain boundary is 5 nm or less. The crystal grain boundary is a discontinuous layer which does not continue the orientation of adjacent crystal grains.