Patent ID: 8524509

Claim:
A method for forming a ferroelectric spontaneous polarization reversal, comprising the steps of: forming a concave portion on a top face of a ferroelectric substrate or a bottom face of a ferroelectric substrate, and applying an electric field into the substrate, wherein a ferroelectric spontaneous polarization reversal is formed at least in one portion of a region of said substrate with said concave portion, and wherein a shape of said concave portion is configured such that a width of said concave portion gets narrower gradually toward an inside of the substrate, and after said ferroelectric spontaneous polarization reversal has been formed, making into almost a flat-plane the top face of the substrate or the bottom face of the substrate in which said concave portion had been formed, and then, forming a new concave portion in a region where no concave portion was formed previously, and then applying an electric field into said substrate to form a ferroelectric spontaneous polarization reversal again at least in one portion of the region of the substrate having said new concave portion.