Semiconductor devices and methods of manufacturing the semiconductor devices are provided. The methods may include forming a sacrificial gate pattern on a substrate, forming a first spacer on a sidewall of the sacrificial gate pattern and forming a first interlayer dielectric (ILD) layer covering a sidewall of the first spacer and exposing a top surface of the first spacer. The first spacer may expose an upper portion of the sidewall of the sacrificial gate pattern. The methods may also include forming a capping insulating pattern covering top surfaces of the first spacer and the first ILD layer, replacing the sacrificial gate pattern with a gate electrode structure and patterning the capping insulating pattern to form a second spacer on the first spacer and between the gate electrode structure and the first ILD layer. The second spacer may be formed of a material having a dielectric constant higher than a dielectric constant of the first spacer.