A method of forming a semiconductor device. The method comprises steps of providing a substrate having a first transistor, a second transistor and non-salicide device formed thereon and the conductive type of the first transistor is different from that of the second transistor. A buffer layer is formed over the substrate and a tensile material layer is formed over the buffer layer. A portion of the tensile material layer over the second transistor is thinned and a spike annealing process is performed. The tensile material layer is removed to expose the buffer layer over the substrate and a patterned salicide blocking layer is formed over the non-salicide device. A salicide process is performed for forming a salicide layer on a portion of the first transistor and the second transistor.