Semiconductor devices include a strain-inducing layer capable of applying a strain to a channel region of a transistor included in a miniaturized electronic device, and a method of manufacturing the semiconductor device. The semiconductor device includes a substrate having a channel region; a pair of source/drain regions provided on the substrate and arranged on both sides of the channel region in a first direction; and a gate structure provided on the channel region and comprising a gate electrode pattern extending in a second direction that is different from the first direction, a gate dielectric layer disposed between the channel region and the gate electrode pattern, and a gate spacer covering respective lateral surfaces of the gate electrode pattern and the gate dielectric layer. At least one of the source/drain regions includes a first strain-inducing layer and a second strain-inducing layer. The first strain-inducing layer is disposed between a lateral surface of the channel region and the second strain-inducing layer and contacts at least a portion of the gate dielectric layer.