Plasma etching can cause damage in gate oxide during ULSI processing. The damage in the oxide is believed to arise through a high field induced stress current. However, there is another type of damage which is due to ion and photon bombardment on the edge of poly-Si gate during the plasma etching. These two damage mechanisms impose different reliability problems. One is hot-carrier(HC) stress and the other is Fowler-Nordheim(F-N) stress. MOS devices with special test structures to assess plasma process damage were fabricated using 0.35 μm CMOS technology. The devices with different poly gate antennas and etching through different poly-Si gate etching conditions were studied using SEM and various electrical techniques. It was found that oxide charging damaged device is more susceptible to F-N type of stress while ion and photon bombardment damaged device is more susceptible to HC type of stress.