A method of forming a bit line of a semiconductor memory device is performed as follows. A first interlayer insulating layer is formed over a semiconductor substrate in which an underlying structure is formed. A region of the first interlayer insulating layer is etched to form contact holes through which a contact region of the semiconductor substrate is exposed. A low-resistance tungsten layer is deposited on the entire surface including the contact holes, thus forming contacts. A CMP process is performed in order to mitigate surface roughness of the low-resistance tungsten layer. The low-resistance tungsten layer on the interlayer insulating layer is patterned in a bit line metal line pattern, forming a bit line.