Influence of the parameters of plasma enhanced chemical vapor deposition （PECVD） on the surface morphology of hydrogenated amorphous silicon （α-Si：H） film was investigated. The root-mean-square （RMS） roughness of the film was measured by atomic force microscope （AFM） and the relevant results were analyzed using the surface smoothing mechanism of film deposition. It is shown that an α-Si：H film with smooth surface morphology can be obtained by increasing the PH3/N2 gas flow rate for 10% in a high frequency （HF） mode. For high power, however, the surface morphology of the film will deteriorate when the Sill4 gas flow rate increases. Furthermore, optimized parameters of PECVD for growing the film with smooth surface were obtained to be Sill4：25 sccm （standard cubic centimeters per minute）, At： 275 sccm, 10%PH3/N2：2 sccm, HF power： 15 W, pressure： 0.9 Torr and temperature： 350℃. In addition, for in thick fihn deposition on silicon substrate, a N20 and NH3 preprocessing method is proposed to suppress the formation of gas bubbles.
