Epitaxial Co70Fe30 films with the bcc structure were grown on a Si(001) substrate with TiN as a buffer by sputtering technique. The x-ray diffraction results confirmed the epitaxial nature of the films and the crystallographic relationship was determined as Co70Fe30(002)<110>//TiN(002)<100>//Si(004)<100>. The surface morphology characterized by atomic force microscopy on our films revealed that smooth surfaces could be obtained at growth temperatures below 350 °C. The strain state of 60 nm epitaxial Co70Fe30 films was studied as a function of growth temperature. Magnetization hysteresis loops of the films grown at 300 °C were measured using superconducting quantum interface device magnetometer.