Dummy gate structures and manufacturing methods thereof

A method for manufacturing a semiconductor device, the method comprising:

• providing a semiconductor structure including a semiconductor substrate, one or more fins protruding from the semiconductor substrate, a trench on opposite sides of the one or more fins, a first insulator layer partially filling the trench, and a second insulator layer on the one or more fins, the one or more fins protruding from the first insulator layer;
• forming a plurality of dummy gate structures associated with the one or more fins, the plurality of dummy gate structures including at least a first dummy gate structure on the first insulator layer and a second dummy gate structure on the second insulator layer, the first and second dummy gate structures being spaced apart from each other, the first dummy gate structure adjacent to a portion of the second insulator layer on a side surface of the one or more fins;
• forming a spacer on side surfaces of the dummy gate structures;
• etching a portion of the second insulator layer and a portion of the one or more fins not covered by the spacer and the plurality of dummy gate structures to form a recess;
• and
• forming a source or a drain in the recess.