Patent ID: 8530321

Claim:
A method of manufacturing a variable resistance element comprising: wherein M is a transition metal element and O is oxygen; forming a lower electrode material layer; forming on the lower electrode material layer, a first oxide material layer comprising MO x wherein a content ratio of O with respect to M is x (x: positive number), and a second oxide material layer comprising MO y wherein a content ratio of O with respect to M is y (y>x), in this order; forming an upper electrode material layer on the second oxide material layer; forming a protective material layer on the upper electrode material layer, the protective material layer having a composition different from a composition of the upper electrode material layer; patterning the lower electrode material layer, the first oxide material layer, the second oxide material layer, the upper electrode material layer, and the protective material layer in a predetermined shape to form a lower electrode, a first oxide layer, a second oxide layer, an upper electrode, and a protective layer, respectively; forming an interlayer insulating layer such that the interlayer insulating layer covers the protective layer; forming an upper contact hole such that the upper contact hole penetrates the interlayer insulating layer, the protective layer is exposed on a bottom of the upper contact hole, and the upper electrode is not exposed on the bottom of the upper contact hole; forming an upper contact plug inside the upper contact hole; and heating the upper electrode to form a plurality of hillocks which protrude into the second oxide layer and do not pierce the second oxide layer, on grain boundaries of a material constituting the upper electrode, and forming a plurality of concave portions in the second oxide layer, respectively, on an interface between the second oxide layer and the upper electrode such that the plurality of concave portions correspond to the hillocks, respectively.