A method for manufacturing a semiconductor memory device using asymmetric junction ion implantation, including performing ion implantation for adjusting a threshold voltage to a semiconductor substrate, forming a gate stack on the semiconductor substrate to define a storage node junction region and a bit line junction region, implanting a first conductive impurity ion and a second conductive impurity ion using a mask layer pattern covering the storage node junction region while exposing the bit line junction region, forming a gate spacer layer at both sides of the gate stack, and implanting the first conductive impurity ion using the gate stack and the gate spacer layer as an ion implantation mask layer to form a storage node junction region and a bit line junction region having different impurity concentrations, and different junction depths from each other.