A method for manufacturing a recess gate in a semiconductor device includes forming a device isolation structure on a substrate to define an active region, forming a hard mask pattern over the substrate to selectively expose at least a portion of the active region, forming a recess pattern in the active region through an etching process using the hard mask pattern as an etch barrier, removing the hard mask pattern, forming a gate insulating layer over the substrate, and forming a gate electrode over the gate insulating layer to cover at least the recess pattern.