1. A method of forming a non-volatile memory device, comprising: forming a first dielectric layer over a surface region of a semiconductor substrate; forming a first wiring layer comprising an aluminum material over the first dielectric layer; forming a silicon layer over the first wiring layer; performing an anneal process to form an intermix region from a portion of the silicon layer and a portion of the aluminum material, wherein the intermix region comprises: a polycrystalline silicon layer having a p+ impurity characteristic, wherein a p+ impurity for the polycrystalline silicon layer is derived from an aluminum species from the aluminum layer; forming a resistive switching layer comprising an amorphous silicon material over the polycrystalline silicon layer having the p+ impurity characteristic; and forming a second wiring layer comprising a metal material over the resistive switching layer.