PURPOSE: A method for depositing a cyclic thin film is provided to obtain high film quality and step coverage by forming an insulation layer with silicon under a plasma atmosphere. CONSTITUTION: A silicon thin film is formed on a substrate loaded in a chamber(S200). Silicon is deposited on the substrate by injecting silicon precursor into the chamber to deposit silicon(S210). A non-reactive silicon precursor and a reactive by-product are removed after the silicon is deposited on the substrate(S220). A silicon thin film is comprised of the insulation layer including silicon(S300). The reactive by-product and reactive gas or ignition gas are removed from the chamber(S400). The above S300 and S400 steps are repeated(S500).
