Leakage current mechanisms in sub-50 nm recess-channel-type DRAM cell transistors with three-terminal gate-controlled diodes

Abstract

We investigated the leakage mechanism in the recently developed DRAM cell transistors having deeply recessed channels for sub-50nm technology using a gate-controlled diode method. The identification and modeling of the various leakage components in DRAM cell transistors with three-dimensional structures is of great importance for the estimation of their data retention characteristics. Our study reveals that there is a significant difference in the leakage mechanisms of planar and recessed channel MOSFETs, due to their different geometrical aspects. The leakage current at the extended gate–drain overlapping region in recessed channel MOSFETs is of particular importance from the viewpoint of their refresh modeling. The information on the leakage characteristics of three-dimensional DRAM cell transistors obtained herein will be very useful for refresh modeling and future DRAM device designs.