Improvement of AC characteristics of FITMOS

The AC characteristics of a FITMOS (Floating Island and Thick bottom oxide trench gate MOSfet) with passive hole gate structures are investigated under limiting conditions of high voltage, high temperature and long trench length. The origin of time delay in the switching operation is discussed based on the experimental results and new device structures applicable to the high voltage and high temperature operation are proposed. No additional switching delay is observed in the new structure. Furthermore, degradation in the drain-source breakdown characteristic, as well as the characteristics for the unclamped inductive switch test, is observed.