Thin polyoxide on the top of poly-Si gate to suppress boron penetration for pMOS

A method of using a thin oxide on the top of the poly-Si gate to getter fluorine for BF/sub 2//sup +/ in pMOS is proposed and demonstrated. Due to less amount of fluorine in the poly-Si as well as in the gate oxide, the boron penetration through the gate oxide is suppressed. The MOS capacitors fabricated by using this method show less shifts and distortion on C-V curves and better electrical characteristics.<
>