Abstract: A non-volatile semiconductor memory device includes an interlayer dielectric film 9, 19 flattened by etching back an SOG film. In the non-volatile semiconductor memory device, a barrier film of a silicon nitride film 9D and 19D is formed to cover at least a memory cell composed of a floating gate 4, a control gate 6, etc. Because of such a structure, even if H or OH contained in the SOG is diffused, it will not be trapped by a tunneling film 3. This improves a “trap-up rate”. The barrier film may be formed in only an area covering the memory cell. This reduces its contact area with a tungsten silicide film, thereby suppressing film peeling-off. Thus, the operation life of the memory cell in the non-volatile semiconductor memory device can be improved.