Current-crowding effect in diagonal MOSFET's

Electrical and reliability characteristics of diagonally shaped n-channel MOSFETs have been extensively investigated. Compared with the conventional device structure, diagonal MOSFETs show longer device lifetime under peak I/sub sub/ condition (V/sub g/=0.5 V/sub d/). However, in the high-gate-bias region (V/sub g/=V/sub d/), diagonal MOSFETs exhibit a significantly higher degradation rate. From the I/sub sub/ versus gate voltage characteristics, this larger degradation rate under high gate bias is concluded to be due mainly to the current-crowding effect at the drain corner. For a cell-transistor operating condition (V/sub g/>V/sub d/), this current-crowding effect in the diagonal transistor can be a serious reliability concern.<>