1. A semiconductor device comprising: a semiconductor layer; a first dielectric film provided on said semiconductor layer; a first gate electrode provided on said first dielectric film; at least one second gate electrode provided opposite said first gate electrode to receive an input signal; at least one second dielectric film intervening between said first gate electrode and at least one said second gate electrode; a third gate electrode provided opposite said first gate electrode; a ferroelectric film intervening between said first gate electrode and said third gate electrode; and an output portion connected to a part of said semiconductor layer for outputting an output signal according to the input signal inputted in at least one said second gate electrode, wherein there is provided a learning ability for strengthening or weakening a correlation between said input signal and said output signal according to polarization characteristics of said ferroelectric film.