Disclosed are semiconductor devices and/or method of fabricating the same. The semiconductor device comprises a substrate including first and second regions, a first active pattern on the first region and including a pair of first source/drain patterns and a first channel pattern including first semiconductor patterns, a second active pattern on the second region and including a pair of second source/drain patterns and a second channel pattern including second semiconductor patterns, a support pattern between two vertically adjacent first semiconductor patterns, and a first gate electrode and a second gate electrode on the first channel pattern and the second channel pattern. A channel length of the first channel pattern is greater than that of the second channel pattern. A ratio of a width of the support pattern to the channel length of the first channel pattern is in a range of 0.05 to 0.2.