CoSi2, or TiSi2 formation on gate polysilicon can degrade the current-voltage and capacitance-voltage characteristics of MOS capacitors. Degradation of the gate oxide breakdown field is much more severe for capacitors with TiSi2 than for those with COSi2 TEM reveals evidence for a reaction at the interface between TiSi2 and SiO2, whereas there is no observable reaction between COSi2 and SiO2- The low breakdown fields for devices with TiSi2 may be due to thinning of the gate oxide by the interfacial reaction or mechanical deformation. A high density of electron traps and a small reduction in the breakdown field is observed when COSi2 contacts the gate, possibly due to a compressive stress in the oxide exerted by the suicide. In addition, an increase in the interface state density at the Si-SiO2 interface is seen for all samples exposed to a rapid thermal anneal (RTA) at 800°C, possibly due to the release of H from dangling bonds.