A semiconductor device includes an active region defined by an element isolation region in a base substrate, source and drain regions of a first conductivity type spaced apart from each other, and formed in the active region, a body region of a second conductivity type surrounding the source region, and formed in the base substrate, a drift region of the first conductivity type surrounding the drain region, having a lower impurity concentration than the drain region, and formed in the base substrate, an insulating structure including a buried insulating pattern and a semiconductor pattern sequentially stacked on the drift region, a gate dielectric film including a first portion extending along an upper surface of the body region and a second portion extending along a side surface and an upper surface of the insulating structure, and a gate electrode extending along an upper surface of the gate dielectric film.