A method for manufacturing a semiconductor device includes forming a first semiconductor layer, forming a stacked body including alternately formed first and second layers on the first semiconductor layer, forming a hole from an upper surface of the stacked body to the first semiconductor layer to expose the first semiconductor layer therein. A first insulating layer is formed on the inner wall of the hole, and a second semiconductor layer is formed on the first insulating layer within the hole, wherein the second semiconductor layer is electrically connected to the first semiconductor layer. A metal layer is provided in contact with at least one of the first and second semiconductor layers. The stacked body, semiconductor layers, insulating layer and metal layer are exposed to an annealing temperature sufficient to cause migration of metal in the metal layer into one of the first and second semiconductor layers.