A semiconductor device includes a gate pattern disposed on a semiconductor substrate, a gate spacer disposed on both sidewalls of the gate pattern, and a fixed charge layer disposed in the semiconductor substrate below the gate spacer. Elements generating fixed charges are injected into the fixed charge layer. A layer in which carriers induced by the fixed charge layer are accumulated is disposed below the fixed charge layer. The elements are segregated to a substrate of the semiconductor substrate from the inside of the semiconductor substrate by heat.