A semiconductor device includes first active patterns on a PMOSFET section of a logic cell region of a substrate, second active patterns on an NMOSFET section of the logic cell region, third active patterns on a memory cell region of the substrate, fourth active patterns between the third active patterns, and a device isolation layer that fills a plurality of first trenches and a plurality of second trenches. Each of the first trenches is interposed between the first active patterns and between the second active patterns. Each of the second trenches is interposed between the fourth active patterns and between the third and fourth active patterns. Each of the third and fourth active patterns includes first and second semiconductor patterns that are vertically spaced apart from each other. Depths of the second trenches are greater than depths of the first trenches.