This application provides a gradient-doped ferroelectric thin film device and its fabrication method, relating to the field of optoelectronic device technology. The gradient-doped ferroelectric thin film device comprises, from bottom to top, a substrate, a
buried oxide layer, a buffer layer, and a ferroelectric thin
film material layer; the ferroelectric thin
film material layer is doped with
impurity ions, with the
doping concentration of the
impurity ions increasing sequentially from bottom to top. This application, by employing a bottom-up incremental gradient
doping design, optimizes the interface defects and
internal stress of the ferroelectric thin film, overcomes the problem of
lattice mismatch between ordinary
ferroelectric thin films and the substrate layer, achieves improved
crystal quality and enhanced electro-optic coefficient, and effectively improves the electro-optic effect.