Epitaxial growth of a Co-doped anatase TiO2 thin film on silicon has been achieved by using SrTiO3/TiN bilayers as a buffer. All layers were sequentially formed by pulsed laser deposition. X-ray Φ scan and selective area electron diffraction patterns revealed that SrTiO3/TiN buffer layers were grown with a cube-on-cube orientation relationship with silicon. Ferromagnetism was observed at room temperature with a coercivity of around 607 Oe. However, the ferromagnetism is attributed to the highly cobalt enriched TiO2 clusters which nucleate after a certain growth of film, as observed by atomic/magnetic force microscopy as well as cross-sectional transmission electron microscopy. © 2004 American Institute of Physics.