A semiconductor device includes a gate trench formed in a substrate, a gate dielectric layer formed along profile of sidewalls and a bottom surface of the gate trench, first and second gate electrodes that are stacked over the gate dielectric layer to gap-fill a portion of the gate trench, a dipole inducing portion positioned between the second gate electrode and the gate dielectric layer and including a dipole bond and a non-dipole bond, and a capping layer suitable for gap-filling a remaining portion of the gate trench over the dipole inducing portion and the second gate electrode.