Integrated circuit devices including contacts and methods of forming the same are provided. The devices may include a fin on a substrate, a gate structure on the fin and a source/drain region in the fin at a side of the gate structure. The devices may further include a contact plug covering an uppermost surface of the source/drain region and a sidewall of the gate structure. The contact plug may include an inner portion including a first material and an outer portion including a second material different from the first material. The outer portion may at least partially cover a sidewall of the inner portion, and a portion of the outer portion may be disposed between the sidewall of the gate structure and the sidewall of the inner portion.