A vertical non-volatile memory device includes a substrate, and a first stack of word lines and a second stack of word lines extending in a first direction on the substrate and separated from each other in a second direction perpendicular to the first direction. The device further includes first array lines extending in the second direction on the first and the second stack, and connected to word lines of the first and the second stack through at least two of first via contacts in a same level. The device further include first word select lines being in a same level and extending in the first direction, and connected to each of the first array lines through at least one of second via contacts. Ends of each of the first and the second stack have a form of stairs on the substrate.