Abstract: A semiconductor device and a method for fabricating the same is provided. The semiconductor device includes a lower semiconductor film, a buried insulating film, and an upper semiconductor film which are sequentially stacked; an element isolation film defining an active region inside the substrate and including a material having an etching selectivity with respect to silicon oxide; a first gate trench inside the upper semiconductor film; a first gate electrode filing a part of the first gate trench; a second gate trench inside the element isolation film; and a second gate electrode filling a part of the second gate trench, a bottom side of the element isolation film being inside the lower semiconductor film.