Methods of fabricating a semiconductor device are provided. The methods may include forming a gate structure on a core-peri region of a substrate. The substrate may further include a cell region. The methods may also include forming a gate spacer on a sidewall of the gate structure, forming a first impurity region adjacent the gate spacer in the core-peri region of the substrate by performing a first ion implantation process, removing the gate spacer, forming a second impurity region in the core-peri region of the substrate between the gate structure and the first impurity region by performing a second ion implantation process, forming a stress film on the gate structure, an upper surface of the first impurity region, and an upper surface of the second impurity region, and forming a recrystallization region by crystallizing the first impurity region and the second impurity region by performing an annealing process.