Isolation structures

A method, comprising:

• forming a fin-like structure over a substrate;
• forming an isolation feature over the substrate and adjacent to the fin-like structure;
• forming a first dummy gate structure across the fin-like structure, wherein the first dummy gate structure comprises a first portion disposed directly over the fin-like structure and a second portion disposed directly over a first portion of the isolation feature;
• forming source/drain features adjacent to the first portion of the first dummy gate structure;
• forming a mask film to cover the first portion of the first dummy gate structure while exposing the second portion of the first dummy gate structure;
• removing the second portion of the first dummy gate structure and the first portion of the isolation feature thereunder to form a first gate isolation trench;
• forming a first gate isolation structure in the first gate isolation trench;
• and
• replacing the first portion of the first dummy gate structure with a first gate stack, wherein a height of the first gate isolation structure is greater than a height of the first gate stack.

A semiconductor structure, comprising:

• a first vertical stack of channel members disposed over a substrate;
• a first gate stack wrapping around each channel member of the first vertical stack of channel members;
• first source/drain features coupled to the first vertical stack of channel members and adjacent the first gate stack;
• a second vertical stack of channel members disposed over the substrate and spaced apart from the first vertical stack of channel members;
• a second gate stack wrapping around each channel member of the second vertical stack of channel members;
• second source/drain features coupled to the second vertical stack of channel members and adjacent the second gate stack;
• and
• a first isolation structure disposed between and in direct contact with the first gate stack and the second gate stack and extending into the substrate,
• wherein the first gate stack is isolated from the second gate stack by the first isolation structure, and wherein, in a top view, the first isolation structure, the first gate stack, and the second gate stack extend lengthwise along a same direction.