A vertical semiconductor device includes odd and even cell blocks, and odd and even block pad structures. Each of the odd cell blocks includes first conductive line structures including conductive lines and insulation layers alternatively stacked in a first direction. Each of the even cell blocks includes second conductive line structures having substantially the same shape as the first conductive line structures. The odd block pad structure is connected to first edge portions of the first conductive line structures. The even block pad structure is connected to second edge portions, opposite the first edge portions, of the second conductive line structures. Each of the odd cell blocks and the even cell blocks has a first width in a third direction. Each of the odd and even block pad structures is formed on a region of a substrate having a second width greater than the first width in the third direction.