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The combined effects of the fixed-field oxide change and of the edge contour and impurity profile on MOSFET characteristics are considered, and results are presented which give new insight into the performance of MOSFET devices. It was found that this oxide charge lowers the threshold potential, resulting in an increase in conductivity towards and the two edges of the channel along the width direction. As a consequence, the geometric channel pinchoff locus shifts towards the drain as the channel edge is approached. The oxide charge and the net impurity profile under the field region adjacent to the channels causes the current density to increase gradually towards the edges of the channel, in the channel width direction. At high power densities, this may lead to drain-induced corner breakdown. Further, in the subthreshold region, the electric field at the corner of the drain junction is increased, leading possibly to corner breakdown.
Date of Publication: Feb 1984