Semiconductor device and method for fabricating the same

A method for fabricating a semiconductor device, comprising the steps of:

• a) forming a gate electrode over a semiconductor layer with a gate insulating film interposed between the gate electrode and the semiconductor layer;
• b) forming a first ion-implanted layer in parts of the semiconductor layer that are located beside the gate electrode by ion implanting a first dopant using the gate electrode as a mask;
• c) subjecting the first ion-implanted layer to a first annealing process;
• and
• d) subjecting the semiconductor layer to a second annealing process, thereby forming a heavily doped region out of the first ion-implanted layer after the step c) has been performed,
• wherein the temperature of the second annealing process is higher than the temperature of the first annealing process,
• wherein in the step b), the first dopant is introduced at such a dose that a maximum concentration of the first dopant when the first annealing process is over will be greater than a predetermined percentage of a solid solubility at a process temperature of the first annealing process and that a maximum concentration of the first dopant when the second annealing process is over will be equal to or less than a solid solubility at a process temperature of the second annealing process, and
• wherein in the step d), the second annealing process is performed at the highest process temperature in all process steps succeeding the step b).