The present invention relates to a structure of a memory device. The structure of a memory device includes a substrate, including a bottom electrode layer formed therein. A buffer layer is disposed on the substrate, in contact with the bottom electrode layer. A resistive layer surrounds a whole sidewall of the buffer layer, and extends upward vertically from the substrate. A mask layer is disposed on the buffer layer and the resistive layer. A noble metal layer is over the substrate, and fully covers the resistive layer and the mask layer. A top electrode layer is disposed on the noble metal layer.