A recess gate of a semiconductor device includes: a substrate having a bulb-shaped recess pattern formed therein, wherein the bulb-shaped recess pattern includes a first ball pattern and a second ball pattern formed therein, the first ball pattern having a different diameter than the second ball pattern; a gate insulation layer formed over the bulb-shaped recess pattern and the substrate; and a conductive layer formed over the gate insulation layer and filling the bulb-shaped recess pattern.