Semiconductor device and manufacturing method thereof

A manufacturing method of a semiconductor device, comprising:

• forming a fin structure by using a patterned mask layer, wherein the fin structure comprises semiconductor channel layers and semiconductor sacrificial layers alternatively disposed on top of one another, a topmost layer of the fin structure is one of the semiconductor channel layers, and the patterned mask layer is formed on the topmost layer;
• forming a cladding layer extending along sidewalls of the fin structure;
• performing a first etching process by a first etchant to partially removing the cladding layer and the patterned mask layer;
• and
• performing a second etching process by a second etchant to accessibly expose the topmost layer of the fin structure with cladding spacers extending along the sidewalls of the fin structure, wherein an etch rate of the first etchant for the cladding layer is greater than that of the second etchant for the cladding layer.

A manufacturing method of a semiconductor device, comprising:

• forming a fin structure on a semiconductor substrate by a patterned mask layer, wherein the fin structure comprises semiconductor channel layers and semiconductor sacrificial layers alternately stacked;
• forming isolation structures along sidewalls of the semiconductor substrate;
• forming a cladding layer on the isolation structures and along sidewalls of the fin structure;
• forming dielectric structures on the isolation structures, wherein the dielectric structures are in contact with the cladding layer;
• removing a portion of the cladding layer and the patterned mask layer to accessibly expose a topmost one of the semiconductor channel layers of the fin structure, wherein the portion of the cladding layer is removed to form cladding spacers with concave top surfaces;
• and
• replacing the semiconductor sacrificial layers of the fin structure to form a gate structure wrapping around each of the semiconductor channel layers.