Integrated circuit devices including fin field-effect transistors (finFETs) and methods of forming the same are provided. The methods may include forming a fin-shaped channel region including germanium on a substrate and forming a source/drain region adjacent the channel region on the substrate. The methods may further include forming a barrier layer contacting sidewalls of the channel region and the source/drain region, and the barrier layer may include SixGe1-x, and x may be in a range of about 0.05 to about 0.2.