A semiconductor device including a plurality of buried word lines extending in a first direction and a plurality of buried bit lines extending in a second direction. Upper surfaces of the plurality of buried word lines and the plurality of buried bit lines are lower than an upper surface of a substrate. The distance between two active regions that constitute a pair of first active regions from among a plurality of first active regions included in a first group of active regions is less than the distance between two adjacent active regions having the plurality of buried bit lines therebetween. A method of manufacturing a semiconductor device includes forming a plurality of first trenches in a substrate, forming a plurality of first conductive patterns in the plurality of first trenches in such a manner that a pair of first conductive patterns is disposed in each of the plurality of first trenches, forming a plurality of first buried patterns in the plurality of first trenches to cover the plurality of first conductive patterns, forming a plurality of second trenches by etching the substrate between the plurality of first trenches, and forming a plurality of second buried patterns in the plurality of second trenches.