a substrate comprising a first region and a second region spaced apart from each other;

a first fin-type active region defined by a first device isolation trench in the first region, the first fin-type active region comprising a first fin top surface at a first level;

at least one nanosheet on the first fin top surface;

a first gate line on the first fin-type active region, the first gate line surrounding the at least one nanosheet on the first fin top surface;

a second fin-type active region defined by a second device isolation trench in the second region, the second fin-type active region comprising a second fin top surface higher, relative to a bottom surface of the substrate, than the first fin top surface;

a second gate line on the second fin-type active region, the second gate line surrounding the second fin top surface and sidewalls of the second fin-type active region;

a first insulating structure on a sidewall of the first fin-type active region in the first region; and

a second insulating structure on a sidewall of the second fin-type active region in the second region,

wherein each of the first insulating structure and the second insulating structure comprises:

a lower buried insulating layer comprising a first top surface closer to a bottom surface of the substrate than the first level;

an upper buried insulating layer comprising a second top surface farther from the bottom surface of the substrate than the first top surface; and

an upper insulating liner between the lower buried insulating layer and the upper buried insulating layer.