The epitaxial wafer is expected to become the industry standard for super large-diameter wafers over 300 mm. The demand for reductions in production cost along with stringent quality improvements are driving diameters upward. The super silicon project has developed an epitaxial process, for 300 mm epitaxial wafers, using SiH4 gas at a low temperature just under 1000 degrees C. This process promises to decrease contamination, to prevent slip generation, and to improve productivity. Since the epitaxial layer quality is tightly correlated with the growth process, we also characterized the microdefects and microroughness on the surface of epitaxial wafers that were grown with the SiH4 process. Comparing the results of this experiment with those of a conventional SiHCI3 process, we conclude that the SiH4 process presents no problems when applied to super large-diameter epitaxial wafer production.