Deposition of tungsten films

A method of forming a composite tungsten film, comprising:

• sequentially depositing tungsten nucleation layers and tungsten bulk layers on a substrate to form a composite tungsten layer, wherein each of the tungsten nucleation layers is deposited by alternately adsorbing a tungsten-containing precursor and a reducing gas on the substrate and wherein each of the tungsten bulk layers is deposited by thermally decomposing a gas mixture comprising a tungsten-containing precursor.

A method of forming a composite tungsten film for use in a memory cell, comprising:

• providing a substrate structure, wherein the substrate structure includes an insulating material having at least one aperture therein;
• and
• sequentially depositing tungsten nucleation layers and tungsten bulk layers on a substrate to form a composite tungsten layer, wherein each of the tungsten nucleation layers and the tungsten bulk layers have a thickness less than about 300 Å.