A storage device includes: a substrate; a first conductive layer extending in a first direction; a second conductive layer adjacent to the first conductive layer in a second direction, and extending in the first direction; a third conductive layer extending in a third direction; a fourth conductive layer extending in the second direction; a fifth conductive layer disposed on the second conductive layer, extending in the third direction, and being electrically connected to the fourth conductive layer; a first storage layer disposed between the third conductive layer and the fourth conductive layer; a first semiconductor layer disposed between the first conductive layer and the third conductive layer; a second semiconductor layer disposed between the second conductive layer and the fifth conductive layer; and a first gate electrode extending in the second direction and being shared by side surfaces of the first semiconductor layer and the second semiconductor layer.