A semiconductor memory device is manufactured by: forming a hole by etching an interlayer insulation film formed over a semiconductor substrate; forming a barrier film over the interlayer insulation film including a surface of the hole; forming a first metal film over the barrier film so as to fill in the hole; forming a bit line contact plug in the hole by removing the first metal film and the barrier film so as to expose the interlayer insulation film; carrying out a gas treatment to a surface of the interlayer insulation film including the bit line contact plug so as to promote a growth of metal nucreation; forming a second metal film over the gas treated interlayer insulation film; and forming a bit line in contact with the bit line contact plug by etching the second metal film.