Method for fabricating conductive layer stack and method for fabricating semiconductor device with gate contact

A method for fabricating a semiconductor device, comprising:

• providing a substrate;
• forming a gate structure on the substrate;
• and
• forming a gate contact on the gate structure comprising:
• forming a gate contact barrier layer on the gate structure;
• forming a gate contact intervening layer on the gate contact barrier layer which comprises titanium nitride;
• exposing the gate contact intervening layer to pulses of a germanium-containing reducing agent in a hydrogen environment to form a layer of germanium on the gate contact intervening layer;
• and
• exposing the layer of germanium to pulses of a tungsten-containing precursor to form a gate contact filler layer on the gate contact barrier layer;
• wherein the gate contact barrier layer comprises a columnar grain structure;
• wherein the gate contact intervening layer comprises tungsten silicide, and a thickness of the gate contact intervening layer is greater than about 4.1 nm;
• wherein the gate contact filler layer comprises alpha phase tungsten.