Silicon oxides were rf magnetron sputtered on p-type silicon wafers, and annealed in the temperature range from 700 to 1000 degrees C for furnace annealing and from 950 to 1050 degrees C for rapid thermal annealing. The annealed oxides in metal-oxide-semiconductor structures were stressed with a constant current. Stability was monitored by midgap voltage and interface states density. The optimum condition to achieve the best electrical stability was furnace annealing at about 900 degrees C. It gives the least value of generated interface states and trapped charge after the electrical stress. A close relation between positive charge trapping and interface states generation is observed.