Semiconductor devices and methods of manufacturing thereof

A semiconductor device, comprising:

• a fin structure protruding from a substrate and including semiconductor layers;
• a dummy fin structure extending parallel to the fin structure and including a deformable stress layer;
• an active gate structure overlaying the fin structure;
• a high-k dielectric layer disposed over the dummy fin structure and protruding from a top surface of the active gate structure along a vertical direction;
• and
• a gate cut structure extending from the high-k dielectric layer along the vertical direction.

A method of fabricating a semiconductor device, comprising:

• forming a fin structure protruding from a substrate;
• forming a dummy fin structure that extends parallel to the fin structure, the dummy fin structure including a deformable layer;
• forming a high-k dielectric layer over the dummy fin structure;
• and
• forming an active gate structure overlaying the fin structure, the dummy fin structure defining a sidewall of the active gate structure and the high-k dielectric layer protruding from a top surface of the active gate structure.