A method of manufacturing a semiconductor device includes forming an isolation layer on a substrate, where an active pattern is defined, forming an insulating interlayer on the active pattern of the substrate and the isolation layer, removing portions of the insulating interlayer, the active pattern and the isolation layer to form a first recess, forming a first contact in the first recess on a first region of the active pattern exposed by the first recess, removing portions of the active pattern and the isolation layer in the first recess by performing an isotropic etching process, to form an enlarged first recess, and filling the enlarged first recess to form a first spacer that surrounds a sidewall of the first contact.