Method for manufacturing silicon oxynitride gate oxide layer

The invention provides a method for manufacturing a silicon oxynitride gate oxide layer of an MOS (metal oxide semiconductor) device, and the method comprises the following steps: firstly nitridizing on a provided silicon substrate for forming silicon oxynitride, then performing thermal oxidization for forming a first silicon oxide layer between the silicon oxynitride and the silicon substrate and a second silicon oxide layer on the silicon oxynitride, and then depositing polysilicon on the second silicon oxide layer after secondly annealing the silicon substrate; and etching for forming a gate and the silicon oxynitride gate oxide layer. The silicon oxide layer is introduced between the silicon substrate and the silicon oxynitride, thereby reducing dangling bonds between the silicon oxynitride gate oxide layer and the silicon substrate, further reducing the interface state charge density between the silicon oxynitride gate oxide layer and the substrate and improving certain properties of the MOS device, such