Process for removing seams in tungsten plugs

A MOSFET device structure, with a composite tungsten fill, located in a contact hole, and with said composite tungsten fill comprised of an underlying tungsten liner, and an overlying, dual humped, tungsten shape, comprising:

• field oxide regions on the surface of a semiconductor substrate;
• a device region between said field oxide regions;
• a polysilicon gate structure on said semiconductor substrate, in center of said device region;
• a source/drain region in surface of said semiconductor substrate, between said polysilicon gate structure, and said field oxide regions;
• an insulator layer located on said source/drain region, on said polysilicon gate structure, and on said field oxide regions;
• a contact hole in said insulator layer, exposing a portion of a source region of said source/drain region;
• a titanium layer, contouring only the exposed surfaces of the inside of said contact hole, with said titanium layer, located on the sides of said contact hole, and with said titanium layer, at the bottom of said contact hole, contacting said source region, of said source/drain region;
• a titanium nitride layer, only on said titanium layer;
• said tungsten liner, located only on said titanium nitride layer, not completely filling said contact hole, resulting in a space in the center of said contact hole, with said space narrower than the diameter of said contact hole;
• said dual humped, tungsten shape, on said tungsten liner, filling said space, in center of said contact hole, and extending upwards from said contact hole, with the top surface of each hump, of said dual humped, tungsten shape, at a level higher than the top surface of said insulator layer, and with the space between humps, at the same level as the top surface of said insulator layer;
• and
• an interconnect metallization structure, overlying and contacting said dual humped, tungsten shape, and overlying a portion of the top surface of said insulator layer.