Recent progress in FET (field effect transistor)-type ferroelectric random access memories (FeRAM) is reviewed. Improvement of the data retention characteristics in MFIS (M; metal, F; ferroelectric, I; insulator, S; semiconductor)- and MFMIS-FETs is first described and recent experimental results are presented. Particular attention is paid to high-k dielectrics such as LaAlCb and H1D2, which are used as the insulating buffer layers. Then, it is shown that a lT2C-type cell, in which two ferroelectric capacitors with the same area are connected to the gate of a MOSFET, is useful in improving the data retention characteristics. Finally operation and integration characteristics of the cells are discussed.
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