Metal oxide semiconductor capacitors with oxidized thick and thin nitride films of two different nitride thicknesses were used to study the conduction and charge-trapping behavior under positive stress bias to the upper electrode. Although the top oxide thickness of the two groups of oxidized nitride films is the same, the charge-trapping characteristics are different. It was found that due to the positive stress to the upper electrode of oxidized thick nitride, the gate voltage is shifted to the negative direction, whereas in oxidized thin nitride, it is shifted to the positive direction, just like the nitride films. It was also observed that in nitride films, irrespective of nitride thickness, due to the positive stress bias, the gate voltage is shifted to the positive direction. From the experimental results of oxidized thick and thin nitride, it can be inferred that in oxidized thick nitride, due to electron injection from the lower electrode, holes are generated in the nitride film and are trapped near the interface. As a result of trapped holes near the interface of the top oxide and nitride, as well as a shallow electron trap centered below the conduction band of the nitride, a large increase in current is observed in oxidized thick nitride. On the other hand, in oxidized thin nitride films for the same positive stress bias, only a few holes are generated in the nitride film because most of the injected electrons from the lower electrode tunnel. through the nitride and are trapped in the top oxide. Also shallow trap centers are generated below the conduction band of the thin nitride films. As a result of fewer trapped holes in the interface, the increase of current in oxidized thin nitride is less compared with those of oxidized thick nitride.