Provided is a semiconductor memory device (resistance random access memory element) improved in properties. A Ru film is formed as a film of a lower electrode by sputtering, and a Ta film is formed thereonto by sputtering. Next, the Ta film is oxidized with plasma to oxidize the Ta film. In this way, a compound Ta2O5 is produced and further Ru is diffused into the compound to form a layer (variable resistance layer) in which Ru is diffused into the compound Ta2O5. Such an incorporation of a metal (such as Ru) into a transition metal oxide TMO (such as Ta2O5) makes it possible to form electron conductive paths additional to filaments to lower the filaments in density and thickness. Thus, the memory element can be restrained from undergoing OFF-fixation, by which the element is not easily lowered in resistance, to be improved in ON-properties.