Semiconductor device and method of forming thereof

A method comprising:

• forming a plurality of isolation regions between a plurality of fin structures over a substrate;
• forming a dummy gate structure over the fin structures and the isolation regions;
• forming gate spacers on either side of the dummy gate structure;
• forming a plurality of source/drain epitaxial structures over the fin structures;
• removing the dummy gate structure to form a gate trench between the gate spacers;
• forming a first isolation material in the gate trench;
• etching the first isolation material to form a plurality of first isolation layers between the fin structures and over the isolation regions;
• and
• after forming the plurality of first isolation layers, forming a gate structure over the fin structures.

A device comprising:

• a plurality of fin structures over a substrate;
• a plurality of isolation regions between the fin structures;
• a gate structure over the fin structures;
• a plurality of source/drain epitaxial structures over the fin structures;
• and
• a plurality of first isolation layers between the fin structures and over the isolation regions, wherein the first isolation layers have top surfaces more planar than bottom surfaces of the first isolation layers.