Patent ID: 7494917

Claim:
A method for fabricating a semiconductor device comprising: forming a dielectric layer over a substrate; forming a contact hole in the dielectric layer; forming a barrier layer in the contact hole and on a surface of the dielectric layer; forming a lower conductive layer on the barrier layer to fill the contact hole; wherein the lower conductive layer is formed using a mixture of reactive gases comprising a first source gas and a first reduction gas; removing a portion of the lower conductive layer outside the contact hole to leave a plug in the contact hole; and forming an upper conductive layer on the barrier layer and on the plug, wherein the upper conductive layer is formed using a mixture of reactive gases comprising a second source gas identical to the first source gas and a second reduction gas identical to the first reduction gas, wherein a flow rate of the first source gas is greater than a flow rate of the second source gas, and wherein the first and second reduction gases include hydrogen and SiH 4 , each having a flow rate greater than 0 sccm, the hydrogen flow rate of the first reduction gas used to form the lower conductive layer being the same as the hydrogen flow rate of the second reduction gas used to form the upper conductive layer, and the SiH 4 flow rate of the first reduction gas used to form the lower conductive layer being greater than the SiH 4 flow rate of the second reduction gas used to form the upper conductive layer.