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The data retention characteristics of nitride-based charge trap memories using metal-oxide-nitride-oxide-silicon (MONOS) structures employing high-k dielectrics and high-work-function metal gates have been investigated. The fabricated MONOS devices with structures of TaN/Al 2 O 3 /Si 3 N 4 /SiO 2 /p-Si show fast program/erase characteristics with a large memory window of greater than 6 V at program and erase voltages of AE18 V. From a bake retention test at high temperatures (200, 225, 250, and 275 C), it is expected to take more than 40 years to lose less than 0.5 V charge loss at 85 C. In this paper, we present an optimized cell structure for both improved data retention and erase speed, as well as a systematic study on the charge decay process in MONOS-type flash memory for high-density device applications.

For the first time, multi-level NAND flash memories with a 63 nm design rule are developed successfully using charge trapping memory cells of Si/SiO 2 /SiN/Al 2 O 3 /TaN (TANOS). We successfully integrated TANOS cells into multi-gigabit multi-level NAND flash memory without changing the memory window and circuit design of the conventional floating-gate type NAND flash memories by improving erase speed. The evolved TANOS cells show fourlevel cell distribution which is free from program disturbance and a charge loss of less than 0.4 V at high temperature bake test.