SEMICONDUCTOR DEVICE AND METHOD OF FABRICATING THE SAME

A semiconductor device includes an insulating film formed above an upper surface of a semiconductor substrate and including a contact hole, the contact hole including an upper portion and a lower portion located on the upper portion via a boundary as a first lower end of the upper portion and a first upper end of the lower portion, the boundary including a second inner width same as the first inner width, the lower portion including a second lower end having a third inner width narrower than the second inner width, a first conductive plug made from polycrystalline silicon and formed in the lower portion of the contact hole so that the exposed upper surface of the substrate is in contact with the first conductive plug, and a second conductive plug formed on the first conductive plug and made from a conductive material different from the polycrystalline silicon.