Characterization of midgap tungsten gate MOSFETs

For ultrathin dielectrics, chemical vapor deposition (CVD) is the preferred method to produce low resistivity thin tungsten films. However, with the high interface trap density (D/sub it/) in CVD tungsten gate MOS devices, the degradation of mobility of these devices is expected because of the relation ship /spl mu//sub eff/ =1/(1+/spl alpha/D/sub it/). We show the mobility of thin oxide CVD tungsten gate MOSFETs can be greatly improved by applying a layer of aluminum on the top of a tungsten gate electrode.