Method for manufacturing semiconductor structure with source/drain structure having modified shape

A method for forming a semiconductor structure, comprising:

• forming a fin structure over a substrate longitudinally oriented along a first direction;
• forming a gate structure around a channel region of the fin structure and longitudinally oriented along a second direction;
• forming a first spacer layer in contact with a sidewall of the fin structure in the second direction;
• recessing the fin structure to form a recess;
• forming a first doped region having a first thickness in a third direction in the fin structure under the recess;
• thinning the first doped region to a second thickness in the third direction;
• and
• forming a source/drain structure in the recess.

A method for forming a semiconductor structure, comprising:

• forming a fin structure over a substrate;
• forming an isolation structure around the fin structure;
• forming a gate structure across the fin structure;
• forming spacers on sidewalls of the fin structure;
• recessing the fin structure not covered by the gate structure to form a curved top surface;
• implanting As from the curved top surface to form a doped region;
• etching an upper portion of the doped region;
• and
• forming a source/drain structure over a bottom portion of the doped region after etching the upper portion of the doped region,
• wherein a bottom surface of the bottom portion of the doped region is lower than bottom surfaces of the spacers.