Three mechanisms determining short-channel effects in fully-depleted SOI MOSFETs

Abstract

Mechanisms determining short-channel effects (SCE) in fully-depleted (FD) SOI MOSFETs are clarified based on experimental results of threshold voltage (V/sub T/) dependence upon gate length, and analysis using a two-dimensional (2-D) device simulator. Drain-induced barrier lowering (DIBL) effect is a well known mechanism which determines the SCE in conventional bulk MOSFETs. In FDMOSFETs, two more peculiar and important mechanisms are found out, i.e., the accumulation of majority carriers in the body region generated by impact ionization, and the DIBL effect on the barrier height for majority carriers at the edge of the source near the bottom of the body. Due to these peculiar mechanisms, V/sub T/ dependence upon gate length in the short-channel region is weakened. It is also shown that floating body effects, the scatter of V/sub T/, and transient phenomena are suppressed due to the SCE peculiar to FD MOSFETs.