A piezoelectric device includes a nanoimprinted film which is made from a ferroelectric polymer having a first conformation state and coated on a substrate. The ferroelectric polymer is heated at a temperature between a Curie point (Tc) and a melting point (Tm) of the ferroelectric polymer to cause a change in conformation of the ferroelectric polymer from the first conformation state to a second conformation state, and is then subjected to a nanoimprinting process at an imprinting temperature lower than Tc to cause a change in conformation of the ferroelectric polymer from the second conformation state to a third conformation state that is different from the first conformation state, thereby obtaining the nanoimprinted film.