Semiconductor devices including an isolation insulating pattern on a boundary region of a substrate and between first active patterns and second active patterns

A semiconductor device comprising:

• a substrate including a first region, a second region, and a boundary region between the first region and the second region;
• first active patterns on the first region of the substrate and spaced apart from each other in a first direction parallel to a bottom surface of the substrate;
• second active patterns on the second region of the substrate and spaced apart from each other in the first direction;
• and
• an isolation insulating pattern on the boundary region of the substrate, the isolation insulating pattern between the first active patterns and the second active patterns, wherein
• the isolation insulating pattern is between a corresponding first active pattern of the first active patterns and a corresponding second active pattern of the second active patterns, and
• a bottom surface of the isolation insulating pattern includes a first bottom surface adjacent to the corresponding first active pattern, a second bottom surface adjacent to the corresponding second active pattern, and a protrusion surface protruding from the first bottom surface and the second bottom surface toward an inside of the isolation insulating pattern, wherein
• the protrusion surface includes a first sidewall and a second sidewall,
• the first sidewall protrudes from the first bottom surface toward to the inside of the isolation insulating pattern,
• the second sidewall protrudes from the second bottom surface toward the inside of the isolation insulating pattern, and
• a horizontal distance between the first sidewall and the second sidewall decreases as a vertical level of the protrusion surface increases.