A method is provided for forming a metal silicide layer on a substrate. According to one embodiment the method includes providing the substrate in a process chamber, exposing the substrate at a first substrate temperature to a plasma generated from a deposition gas containing a metal precursor, where the plasma exposure forms a conformal metal-containing layer on the substrate in a self-limiting process. The method further includes exposing the metal-containing layer at a second substrate temperature to a reducing gas in the absence of a plasma, where the exposing steps are alternatively performed at least once to form the metal silicide layer, and the deposition gas does not contain the reducing gas. The method provides conformal metal silicide formation in deep trenches with high aspect ratios.