Semiconductor device and manufacturing method thereof

A method for manufacturing a semiconductor device, comprising:

• forming a semiconductor fin over a substrate;
• forming an isolation feature adjacent the semiconductor fin;
• recessing the isolation feature to form a first recess;
• forming a metal-containing compound mask in the first recess;
• recessing the semiconductor fin to expose a sidewall of the metal-containing compound mask;
• depositing a stress layer over the recessed the semiconductor fin and in contact with the sidewall of the metal-containing compound mask;
• and
• annealing the metal-containing compound mask.

A method for manufacturing a semiconductor device, comprising:

• forming a semiconductor fin over a substrate, wherein the semiconductor fin comprises an epitaxial stack and a semiconductor cap layer over the epitaxial stack;
• forming an isolation feature adjacent the semiconductor fin;
• recessing the isolation feature to form a recess;
• forming a metal-containing compound mask in the recess, wherein the metal-containing compound mask has a first portion and a second portion respectively on opposite sidewalls of the recess;
• and
• annealing the metal-containing compound mask such that the first and second portions of the metal-containing compound mask are merged.