MOSFET drain breakdown voltage

The grounded-gate or gate-assisted drain breakdown voltage of n-channel MOSFET´s has been characterized for wide ranges of oxide thickness and substrate doping concentration. Two distinct regimes, one being channel-doping limited and the other being oxide-thickness limited, have been identified. We propose that these two regimes reflect two possible locations of breakdown-at the n+-p junction and in the deep-depletion layer in the n+ drain. They can be separated by their different breakdown voltage dependences on Vgand require different approaches to process improvement.