A method of fabricating a non-volatile memory device includes: forming a tunnel insulation layer pattern and a floating gate electrode layer pattern over a semiconductor substrate; forming an isolation trench by etching an exposed portion of the semiconductor substrate so that the isolation trench is aligned with the tunnel insulation layer pattern and the floating gate electrode layer pattern; forming an isolation layer by filling the isolation trench with a filling insulation layer; forming a hafnium-rich hafnium silicon oxide layer over the isolation layer and the floating gate electrode layer pattern; forming a hafnium-rich hafnium silicon oxynitride layer by carrying out a first nitridation on the hafnium-rich hafnium silicon oxide layer; forming a silicon-rich hafnium silicon oxide layer over the hafnium-rich hafnium silicon oxynitride layer; forming a silicon-rich hafnium silicon oxynitride layer by carrying out a second nitridation on the silicon-rich hafnium silicon oxide layer; and forming a control gate electrode layer over the silicon-rich hafnium silicon oxynitride layer.