A semiconductor device and a method for fabricating the same are provided. The method includes: forming a plurality of protruded patterns smaller than gate structures by selectively removing predetermined portions of a substrate; and forming the gate structures over the protruded patterns. The semiconductor device includes: a plurality of protruded substrate portions smaller than the gate structures; and a plurality of gate structures encompassing the protruded substrate portions, wherein channels are formed on surfaces of the protruded substrate portion.