Nonvolatile memory element and method for manufacturing same

A method of manufacturing a nonvolatile memory element having variable resistance, the method comprising:

• forming a lower electrode layer above a substrate;
• forming a variable resistance layer on the lower electrode layer, the variable resistance layer comprising an oxygen-deficient transition metal oxide;
• forming an upper electrode layer on the variable resistance layer;
• forming a hard mask layer on the upper electrode layer;
• forming a photoresist mask on the hard mask layer, the photoresist mask having a rounded shape in planar view;
• forming a hard mask by performing etching on the hard mask layer, using the photoresist mask;
• and
• forming a nonvolatile memory element including the upper electrode layer, the variable resistance layer, and the lower electrode layer, by performing etching, using the hard mask, on the upper electrode layer, the variable resistance layer, and the lower electrode layer, with an etching gas that contains an oxygen deficiency-suppressing gas, the nonvolatile memory element having a rounded shape in planar view.