A method of fabricating a semiconductor device includes forming a stacked structure in which 2n (here, n is an integer which is 2 or more) deposited sacrificial layers and 2n deposited insulating layers disposed on the 2n deposited sacrificial layers respectively are alternately deposited in a third direction perpendicular to a first direction and a second direction on a substrate having an upper surface extending in the first and second directions which are perpendicular to each other. Methods include forming a recess group including 2n−1 first recesses penetrating 20 through 2n−1 deposited sacrificial layers and forming a buried insulating layer group including 2n−1 buried insulating layers filling the 2n−1 first recesses respectively. A contact plug group including 2n contact plugs penetrating an uppermost deposited insulating layer of the 2n deposited insulating layers and the 2n−1 buried insulating layers may be formed.