Semiconductor device including field effect transistor and method of forming the same

A method of forming a semiconductor device, comprising:

• forming a gate pattern on a substrate, the gate pattern including a gate insulator and a gate electrode stacked on the substrate;
• etching a substrate adjacent to opposite sides of the gate pattern to form a recess region;
• forming a source/drain pattern of silicon-germanium doped with dopants to fill the recess region;
• forming a capping layer of silicon-germanium on the source/drain pattern;
• forming a metal layer on the capping layer;
• and
• reacting the metal layer with the capping layer by performing an annealing process to form a metal germanosilicide layer,
• wherein a proportion of germanium amount to the sum of the germanium amount and silicon amount in the capping layer is lower than that of germanium amount to the sum of the germanium amount and silicon amount in the source/drain pattern.