A method of fabricating a semiconductor device includes providing a substrate that includes first and second main regions and a dummy region, and forming dummy active patterns on the dummy region. The first and second main regions are spaced apart from each other in a first direction and the dummy region includes a dummy connection region between the first and second main regions and first and second dummy cell regions spaced apart from each other in a second direction. First dummy active patterns, second dummy active patterns, and connection dummy active patterns connecting some of the first dummy active patterns to some of the second dummy active patterns are provided on the first and second dummy cell regions and the dummy connection region, respectively.