Work Function Engineering to Improve Data Retention Due to Floating Body in 3-D GAA Stacked Nanosheet Based DRAM

Following the pivotal success of 3-D NAND technology, which revolutionized flash memory, DRAM technology could similarly advance by adopting vertical stacking of memory cells, employing gate-all-around (GAA) nanosheet as access transistors. Despite its advantages, vertically stacked DRAM with GAA nanosheets may experience challenges related to the floating body effect, which can degrade data retention. This article investigates the impact of gate metal work function (WF) on both dynamic retention characteristics caused by the floating body effect and static retention during DRAM hold operations using TCAD simulation. A dual WF metal gate structure is proposed to improve both dynamic and static data retention in GAA nanosheet-stacked DRAM. The proposed technique has a high potential to address the floating body-induced issues in vertically stacked DRAM for future technology nodes.