Ultrathin Si oxynitride (SiOchiNy) films have been identified as leading candidates to replace conventional SiO2 gate dielectrics in current and future ultralarge-scale integrated circuits. Remote plasma processes to nitridate the top surface of thermally grown oxides have been developed and employed in complementary metal-oxide-silicon device applications. However, it is very difficult to control the nitrogen depth profile in ultrathin Si oxynitride film rising plasma processing and there are many serious problems, such as plasma radiation damage and increases in interface state density due to the N penetrating into the SiO2-Si interface. To overcome these problems, we propose the use of pulse-time-modulated N-2 neutral beams. We first found that the nitrogen depth profile in ultrathin Si oxynitride film could be controlled by changing the pulse-on time and source power in the pulse-time-modulated N-2 neutral beams. We speculated that injected N-2 was diffused due to the surface activation with the energetic neutral beam at a time constant of a few tens of microseconds in the thermal SiO2 film. Additionally, by increasing the substrate temperature to 300 degreesC, SiO-N bonds were effectively formed and a shallower, sharper, and higher density N concentration profile in a thin 2 nm SiO2 film was produced using a pulsed N-2 neutral beam. (C) 2004 American Vacuum Society.