Abstract: A semiconductor device includes: a first insulation layer disposed on a substrate; a lower gate pattern disposed on the first insulation layer; a second insulation layer covering at least a portion of the lower gate pattern; a first lower gate insulation layer disposed on the lower gate pattern and the second insulation layer; a source pattern and a drain pattern disposed on the first lower gate insulation layer, wherein the source pattern and the drain pattern are spaced apart from each other to include a trench facing the lower gate pattern; an oxide semiconductor layer formed along surfaces of the source and drain patterns and a bottom surface of the trench; an upper gate insulation layer disposed on the oxide semiconductor layer; and an upper gate pattern disposed on the upper gate insulation layer and filling the trench.