Abstract: A semiconductor device includes: a substrate including a trench; a bottom gate electrode suitable for gap-filling a lower portion of the trench and including a silicon-doped first metal nitride; and a top gate electrode formed over the bottom gate electrode, and including a silicon-doped second metal nitride having a higher silicon content than a silicon content of the bottom gate electrode and having a higher ratio of a metal content to a nitrogen content than a ratio of a metal content to a nitrogen content of the bottom gate electrode.

Abstract: Embodiments of the present invention provides a semiconductor device with improved electrical characteristics and a method of fabricating the same. A semiconductor device according to an embodiment of the present invention comprises: a substrate including a trench; a gate dielectric layer formed along a sidewall surface and a bottom surface of the trench; a lower gate electrode filling a lower portion of the trench over the gate dielectric layer and formed of a first metal nitride, the first metal nitride having a first grain size; an upper gate electrode partially filling the trench over the lower gate electrode, including a low work function control element, and formed of a second metal nitride, the second metal nitride having a second grain size bigger than the first grain size; and a capping layer gap-filling the remainder of the trench over the upper gate electrode.