Effects of poly-gate doping concentration on plasma charging damage in ultrathin gate oxides were investigated. While the charge-to-breakdown (Q(bd)) value under gate injection stress polarity (-V-g) is independent of the doping concentration, eb, under substrate injection stress polarity (+V-g) shows a noticeable improvement with increasing doping concentration. However, our results show that plasma-induced oxide degradation is actually aggravated with increasing poly-gate doping concentration. These seemingly inconsistent observations can be explained by the lowering of plasma charging potential in the case of insufficient poly-gate doping.