A semiconductor memory device including a substrate; an array of memory cells arranged in rows and columns on the substrate, each memory cell comprising a vertical pillar-shaped active region having upper and lower source/drain regions and a channel region, and a gate stack formed around the channel region; a plurality of bit lines on the substrate, each bit line located below a column of memory cells and electrically connected to the lower source/drain regions of the memory cells; and a plurality of word lines on the substrate, each word line extending in a row direction and connected to gate conductors of the memory cells in a row of memory cells, each word line comprising first portions extending along peripheries of the memory cells and second portions extending between the first portions, the first portions of the word line extending in a conformal manner with sidewalls of the upper source/drain regions.