Manufacturing method of integrated circuit structure

A method comprising:

• forming a stacking structure over a substrate, wherein the stacking structure comprises a first sacrificial layer, a first channel layer, a second sacrificial layer, and a second channel layer sequentially stacked from bottom to top;
• forming a dummy gate structure across the stacking structure;
• forming a gate spacer structure surrounding the dummy gate structure;
• removing the dummy gate structure to form a gate trench defined by the gate spacer structure;
• after forming the gate trench, recessing the second channel layer to form a first recess in the second channel layer;
• forming a first dielectric structure in the first recess of the second channel layer;
• after forming the first dielectric structure, removing the first sacrificial layer to release the first channel layer;
• forming a first metal gate structure in the gate trench and surrounding the first channel layer;
• removing the second sacrificial layer to release the second channel layer;
• and
• forming a second metal gate structure in the gate trench and surrounding the second channel layer.

A method comprising:

• forming a stacking structure over a protruding portion of a substrate, wherein the stacking structure comprises a first sacrificial layer, a first channel layer, a second sacrificial layer, and a second channel layer sequentially stacked from bottom to top;
• forming a first isolation structure and a second isolation structure on opposite sides of the protruding portion of the substrate;
• forming a dummy gate structure across the stacking structure;
• forming a gate spacer structure to surround the dummy gate structure;
• removing the dummy gate structure to form a gate trench defined by the gate spacer structure;
• removing the first sacrificial layer to release the first channel layer;
• forming a first metal gate structure in the gate trench and in contact with the first channel layer and the first isolation structure;
• forming a first dielectric structure on a sidewall of the first channel layer after forming the first metal gate structure;
• after forming the first dielectric structure, removing the second sacrificial layer to release the second channel layer;
• and
• forming a second metal gate structure in the gate trench and in contact with the second channel layer and the second isolation structure.