The device characteristics and hot-carrier-induced degradation of high-voltage n-type metal–oxide–semiconductor transistors with traditional and gradual junctions in the drift region are studied in this work. The gradual junction used in this study is realized by self-aligned N− implantation through dual thicknesses of screen oxide during N− drift implantation. Compared with traditional devices, devices with gradual junctions have improved off-state breakdown voltage (V BD) without sacrificing on-state driving current and hot-carrier-induced degradation. More improvement in V BD is observed if the dimensions of the device are larger. The mechanism responsible for V BD improvement in devices with gradual junctions is also investigated by using technology computer-aided-design simulations.