A semiconductor device includes a step-type recess pattern formed in a substrate, a gate electrode buried in the recess pattern and having a gap disposed between the gate electrode and upper sidewalls of the recess pattern, an insulation layer filling the gap, and a source and drain region formed in a portion of the substrate at two sides of the recess pattern. The semiconductor device is able to secure a required data retention time by suppressing the increase of leakage current caused by the reduction of a design rule.