High reliability UMOSFET with oxide-nitride complex gate structure

In 1985, Ueda et al. proposed the UMOSFET structure. For the last ten years, ON resistance of UMOSFET has been much lower than that of planar DMOSFET. However, the reliability of the trench gate characteristics of UMOSFET has not been reported so far. In our experiment, the breakdown voltage of the trench gate was about half that of the planar gate in the same oxide thickness, and the trench gate was easily destroyed by bias stress and thermal stress. The oxide-nitride complex gate structure overcomes these difficulties. Optimizing complex film gate structure, logic level UMOSFET with high gate reliability, same as that of planar MOSFET, can be obtained.