A semiconductor device comprises a plurality of gate structures formed on a substrate, a gate spacer formed on a sidewall of the gate structures, a semiconductor pattern formed on the substrate between the gate structures, a first impurity region and a second impurity region formed in the semiconductor pattern and at surface portions of the substrate, respectively, wherein the first and second impurity regions include a first conductive type impurity, and a channel doping region surrounding the first impurity region, wherein the channel doping region includes a second conductive type impurity.