Recent progress of FET-type ferroelectric memories

Recent progress of FET-type ferroelectric memories is reviewed. It is descr ibed that insersion of a buffer layer between the ferroelectric film and Si substrate is essential in preventing interdiffusion of the constituent ele ments. It is also shown, however, that existence of the buffer layer degrad es the data retention characteristic severely. Necessary conditions to solv e the short retention time problem are discussed, paying particular attenti on to comparison of MFIS (metal-ferroelectric-insulator-semiconductor) and MFMIS structures. Finally, a novel ferroelectric-gate FET is proposed, in w hich the depolarization field is expected not to be generated in the ferroe lectric film.