A laterally diffused metal-oxide-semiconductor device includes a substrate, a gate dielectric layer, a gate polysilicon layer, a source region, a drain region, a body region, a first drain contact plug, a source polysilicon layer, an insulating layer, and a source metal layer. The source polysilicon layer disposed on the gate dielectric layer above the drain region can serve as a field plate to enhance the breakdown voltage and to increase the drain-to-source capacitance. In addition, the first drain contact plug of the present invention can reduce the drain-to-source on-resistance and the horizontal extension length.