Lithium phosphorus oxynitride (Lipon) thin films have been fabricated successfully by nitrogen plasma-assisted deposition of E-beam reactive evaporated Li3PO4 for the first time. The effect of inductively coupled plasma (ICP) powers on the electrical and optical properties of Lipon thin film was investigated. X-ray photoelectron spectra confirmed that the insertion of N into Li3PO4 and N concentration were dependent on ICP powers. Infrared and UV-vis spectrophotometry were used to characterize their optical properties. The electrical properties of the as-deposited Lipon thin films were investigated by impedance spectroscopy and isothermal transient ionic current measurements. (C) 2004 The Electrochemical Society.