Expitaxially oriented growth of diamond film on Si(001) was achieved using hot filament chemical vapor deposition. The epitaxial relationship between the film and the substrate was confirmed by the observation through scanning electron microscopy and high‐resolution transmission electron microscopy (HRTEM) as follows: Dia(001)//Si(001) and Dia⟨110⟩//Si⟨110⟩ with a misorientation angle of 9° between Dia(001) and Si(001). This reports the HRTEM observation of the largest area of the diamond/Si interface (larger than 880 A˚). It demonstrates that the intermediate &bgr;‐SiC layer is unnecessary for achieving diamond epitaxy on Si. Discussion reveals that the value of the misorientation angle between Dia(001) and Si(001) is not unique and should be controlled to deposit single‐crystal diamond films on Si. ©1996 American Institute of Physics.