Semiconductor device having air gap and method of fabricating thereof

A method, comprising:

• forming an active fin structure and a dielectric fin structure over a substrate, wherein the dielectric fin structure comprises a layer of high-k dielectric material;
• providing a first dummy gate structure over the active fin structure and a second dummy gate structure over the layer of high-k dielectric material of the dielectric fin structure;
• recessing source/drain regions of the active fin structure and the dielectric fin structure adjacent the first and second dummy gate structures respectively;
• removing the first dummy gate structure to expose a channel region of the active fin structure and removing the second dummy gate structure, wherein the removing the second dummy gate structure etches an opening in the layer of high-k dielectric material;
• forming a first metal gate structure over the channel region of the active fin structure and forming a second metal gate structure within the opening in the layer of high-k dielectric material;
• after forming the second metal gate structure, reducing a thickness of the layer of high-k dielectric material adjacent the second metal gate structure;
• forming a conductive contact over the dielectric fin structure and spaced a distance from the second metal gate structure;
• and
• forming an air gap structure in the distance.

A semiconductor device, comprising:

• a first gate structure over an active fin structure and a second gate structure over a dielectric fin structure;
• a conductive structure over the dielectric fin structure and spaced a distance from the second gate structure, wherein a plurality of dielectric layers is formed in the distance including:
• a high-k dielectric layer abutting sidewalls of the second gate structure;
• a first spacer element adjacent the high-k dielectric layer;
• an air gap adjacent the first spacer element;
• and
• a contact etch stop layer (CESL).