Semiconductor device and method of fabricating the same

A semiconductor device, comprising:

• a substrate;
• an active region extending in a first direction on the substrate;
• and
• a gate line intersecting the active region;
• wherein the gate line comprising:
• a conductive layer extending in a second direction crossing the first direction;
• a first conductive part covering a side surface of a lower portion of the conductive layer and a bottom surface of the conductive layer;
• and
• a second conductive part on the first conductive part and covering a side surface of an upper portion of the conductive layer,
• a first work function of the first conductive part and a second work function of the second conductive part are smaller than a third work function of the conductive layer,
• the first work function of the first conductive part is smaller than the second work function of the second conductive part,
• a top surface of the second conductive part is positioned at a level equal to or higher than a top surface of the conductive layer, and
• the first conductive part and the second conductive part are constituted of same metal or metal nitride, the second conductive part contains a doping element, and the first conductive part does not contain the doping element.