The effect of Ni interlayer on stress level of cobalt silicides was investigated. The X-ray diffraction patterns (XRD) show that low temperature formation of Co1-xNixSi2 Solid solution was obtained while Ni interlayer was present in Co/Si system, which was confirmed by Auger electron spectrum (AES) and sheet resistance measurement. XRD was also used to measure the internal stress in CoSi2 films by a 2 theta(psi) -sin(2)psi method. The result shows that the tensile stress in CoSi2 films evidently decreased in Co/Ni/Si(1 0 0) system. The reduction of lattice mismatch, due to the presence of Ni in CoxNi1-xSi2 solid solution, is proposed to explain this phenomenon. (c) 2005 Elsevier B.V. All rights reserved.