A piezoelectric device includes IDT electrodes and solves various problems resulting from the IDT electrodes. The piezoelectric device has a configuration in which a piezoelectric thin-film and a support are bonded together such that the piezoelectric thin-film is supported by the support. IDT electrodes and interconnect electrodes are provided on a surface of the piezoelectric thin-film that is located on the support side. The piezoelectric thin-film includes a region in which the IDT electrodes are provided and on which no support is provided but an opening is formed. This allows the IDT electrodes and the piezoelectric thin-film and the IDT electrode-formed region of the piezoelectric thin-film to not be in contact with the support, thereby defining a membrane including only the piezoelectric thin-film and the IDT electrodes as elements, the piezoelectric thin-film and the IDT electrodes being disposed therein and being important for properties of the piezoelectric device.