A vertical DMOS device implements one or more deep silicon via (DSV) plugs, thereby significantly reducing the layout area and on-resistance (RDSON) of the device. The DSV plugs extend through a semiconductor substrate to contact a conductively doped buried diffusion region, which forms the drain of the vertical DMOS device. Methods for fabricating the vertical DMOS device are compatible with conventional sub-micron VLSI processes, such that the vertical DMOS device can be readily fabricated on the same integrated circuit as CMOS devices and analog devices, such as lateral double-diffused MOS (LDMOS) devices.