A method of fabricating a nonvolatile memory device includes forming a charge tunneling layer on a semiconductor substrate, forming a charge trapping layer on the charge tunneling layer, forming a first charge blocking layer on the charge trapping layer by supplying a metal source gas and a first oxidizing gas onto the charge trapping layer, forming a second charge blocking layer on the first charge blocking layer by supplying a metal source gas and a second oxidizing gas onto the first charge blocking layer, wherein the second oxidizing gas has a higher oxidizing power as compared to the first oxidizing gas, and forming a gate electrode layer on the second charge blocking layer.