A memory string comprises: a first semiconductor layer having a plurality of columnar portions extending in a perpendicular direction with respect to a substrate, and joining portions joining lower ends of the plurality of columnar portions; a charge storage layer surrounding a side surface of the first semiconductor layer; and a first conductive layer surrounding a side surface of the charge storage layer and functioning as a control electrode of memory cells. A select transistor comprises: a second semiconductor layer extending upwardly from an upper surface of the columnar portions; an insulating layer surrounding a side surface of the second semiconductor layer; a second conductive layer surrounding a side surface of the insulating layer and functioning as a control electrode of the select transistors; and a third semiconductor layer formed on an upper surface of the second semiconductor layer and including silicon germanium.