The Cu/barrier/low-k SiCOH/Si structures were fabricated and their thermal stability was investigated. SiCOH films were deposited by plasma-enhanced chemical vapor deposition using divinyldimethylsilane (DVDMS) and O2. As barrier materials, tungsten and tungsten nitride films were deposited by chemical vapor deposition using W(CO)6 and NH3 sources at 450 °C. Variations of scanning electron microscopy and x-ray diffraction results of Cu/barrier/low-k SiCOH/Si were examined depending on the annealing temperature. Both results showed that W and W2N film were stable up to 500 and above 600 °C, WO3 nanorods were grown from the sample surface. It is thought that the thermal stability of the Cu/barrier/SiCOH/Si structure is closely related with the thermal destruction of the W and WNx films.