The method for forming a semiconductor structure includes first providing a substrate. Then, a TiN layer is formed on the substrate at a rate between 0.3 and 0.8 angstrom/second. Finally, a poly-silicon layer is formed directly on the TiN layer. Since the TiN in the barrier layer is formed at a low rate so as to obtain a good quality, the defects in the TiN layer or the defects on the above layer, such as gate dummy layer or gate cap layer, can be avoided.