The effect of high dose source/drain ion implantation on the defect density of 20 nm CMOS gate oxide was studied. Gate oxide damage was found to be strongly influenced by the photoresist implant mask pattern. A clear field blocking mask is found to be most favorable in terms of capacitor degradation. A major charge dissipation path was found to be surface conduction across the field oxide . Blocking this lateral path by photoresist resulted in reduced gate oxide yield. Wafer holders, depending on configuration and material, showed different charge sinking paths. Blocking of these paths caused additional gate oxide degradation.