REVIEW ON FUTURE FERROELECTRIC NONVOLATILE MEMORY - FERAM - FROM THE POINT-OF-VIEW OF EPITAXIAL OXIDE THIN-FILMS

A new crystal engineering of oxide thin films grown epitaxially was claimed for a future ferroelectric nonvolatile memory (FeRAM) from a point of view of scaling and size effect, and its epitaxial growth technology was reviewed. A few ideal models for epitaxial oxide thin films on Si were proposed as a future oxide-FeR-AM. The results are summarized as follows, (1) Bi layer-structured ferroelectric thin him with c-axis inplane orientation: This structure is not easy to made, but is an ideal model to pick up the merit of ferroelectric anisotoropy. (2) Bi layer-structured ferroelectric thin film with a planar-type, which means that electric field is applied parallel to a him surface: This idea is based on attaching a greater importance to epitaxial growth of a ferroelectric layered oxide, (3) Ferroelectric oxide artificial superlattice thin film: This is basically interesting structure from a point of view of material searching, and has a possibility to create a new function such as ferroelectric properties standing aloof from the conventional size effect. (4) Ferroelectric oxide artificial superlattice thin film with the planar-type: This him includes at least a paraelectric oxide layer, and this may create a new 2-dimensional anisotropy of ferroelectric property as a result.