Oxide precipitate growth in boron-doped Czochralski silicon wafers with resistivities ranging from 6 to 40 m Omega cm has been studied following prolonged annealing from 800 to 1000 degrees C. Transmission electron microscopy revealed that (i) the growth rate of oxide platelet precipitates is proportional to the square root of time in 40 m Omega cm samples and (ii) the precipitate morphology changes from plate to polyhedral and strain around the precipitate decreases during annealing at 900 degrees C in 6, 9, and 18 m Omega cm samples. These results indicate that changes in precipitate morphology occur because the oxygen precipitation and boron atom size effects are enhanced by increasing boron concentration.