Self-Aligned-Gate Metal/Ferroelectric/Insulator/Semiconductor Field-Effect Transistors with Long Memory Retention

Self-aligned-gate Pt/SrBi 2 Ta 2 O 9 /HfAlO/Si metal/ferroelectric/insulator/semiconductor (MFIS) field-effect transistors (FETs) were fabricated. Drain current ( I d ) versus gate voltage curves of the MFIS FETs showed almost the same steepness as that of a non-self-aligned-gate Pt/HfAlO/Si metal/insulator/semiconductor FET. Long retention times with large on- and off-state I d ratios were obtained for the MFIS FETs. The retention times more than 33 days with an on- and off-state I d ratio over 10 5 were demonstrated for the self-aligned-gate MFIS FET with a 2-µm-long and 80-µm-wide gate. This device showed the longest memory retention among all of the ferroelectric-gate FETs reported ever before.