A split gate power transistor includes a laterally configured power MOSFET including a doped silicon substrate having a first doped region and a second doped region of an opposite type as the first doped region, a gate oxide layer formed on a surface of the substrate, and a split polysilicon layer formed over the gate oxide layer. The polysilicon layer is cut into two electrically isolated portions, a first portion forming a polysilicon gate positioned over a channel region and a transition region of the substrate, and a second portion forming a polysilicon field plate formed entirely over a field oxide filled trench formed in the second doped region. The two polysilicon portions are separated by a gap. A lightly doped region is implanted in the substrate below the gap and adjacent to the trench, thereby forming a fill region having the same doping type as the first doped region.