A MOS transistor with stacked nanowires and a method of manufacturing the same. The transistor may include a stack of cascaded nanowires extending in a first direction on a substrate; a gate stack extending in a second direction across the nanowire stack; source and drain regions disposed on opposite sides of the gate stack in the second direction; and a channel region constituted of the nanowire stack between the source and drain regions. The cascaded nanowires can be formed by repeated operations of etching back, and lateral etching and then filling of grooves, thereby increasing an effective width of the channel, increasing a total area of an effective conductive section, and thus improving a drive current.