We investigated the effect of hydrogen annealing in the temperature range from 850 to 1200 degrees C on oxygen precipitation and gate oxide integrity in Czochralski Si wafers. The bulk microdefect density of dynamic random access memory thermal simulation wafers showed a strong dependence on the ramp-up rate conditions of hydrogen annealing. The gate oxide integrity improved after hydrogen annealing at temperatures above 1000 degrees C. However, for better stability of the gate oxide integrity after the heat treatment, higher temperature annealing is necessary. We observed that the effect of hydrogen annealing was limited to the near surface, because the gate oxide integrity of hydrogen-annealed wafers degraded to that for nonannealed wafers after repolishing.