A semiconductor memory device includes a first and second memory cell array region, a first and second sense amplifier region interposed between the first and second memory cell array regions, a first column selection region interposed between the first sense amplifier region and the first memory cell array region and including a first column selection transistor connected between a first bit line and a first local data input/output (I/O) line, and a second column selection region interposed between the second sense amplifier region and the second memory cell array region and including a second column selection transistor connected between a second bit line and a second local data I/O line. A load of the second bit line is larger than a load of the first bit line and a threshold voltage of the first column selection transistor is higher than a threshold voltage of the second column selection transistor.