Semiconductor device and method for forming the same

A method for forming a semiconductor device, comprising:

• forming an active region and an isolation region surrounding the active region on a semiconductor substrate;
• forming a gate stack structure, wherein the gate stack structure is formed on the active region and extends onto the isolation region;
• and
• forming an S/D region, wherein the S/D region is embedded into the semiconductor substrate in the active region and located at both sides of the gate stack structure;
• wherein the step of forming the S/D region comprises:
• determining an interface region comprising the active region of a partial width abutting the isolation region, and forming an auxiliary layer covering the interface region;
• removing the semiconductor substrate of a partial thickness in the active region using the auxiliary layer, the gate stack structure and the isolation region as a mask, so as to form a groove;
• growing a semiconductor material in the groove for filling into the groove;
• and
• removing the auxiliary layer.