Semiconductor device including fin-fet and manufacturing method thereof

A method for manufacturing a semiconductor device, comprising:

• forming a fin structure including a lower layer, an intermediate layer disposed over the lower layer and an upper layer disposed over the intermediate layer;
• partially oxidizing the intermediate layer;
• after the oxidizing, forming a protective layer over the fin structure;
• reducing a height of the protective layer such that the partially oxidized intermediate layer remains covered by the protective layer;
• forming an isolation insulating layer so that the fin structure with the protective layer with the reduced height is embedded in the isolation insulating layer;
• and
• forming a gate structure over the upper layer.

A method for manufacturing a semiconductor device, comprising:

• forming a first fin structure and a second fin structure, each of which includes a lower layer, an intermediate layer disposed over the lower layer and an upper layer disposed over the intermediate layer;
• partially oxidizing the intermediate layer of the second fin structure, while the first fin structure is covered by a cover layer;
• forming a protective layer to fully cover the first fin structure and the second fin structure with partially oxidized intermediate layer;
• reducing a height of the protective layer such that the intermediate layer of the first fin structure and the partially oxidized intermediate layer of the second fin structure remain covered by the protective layer;
• forming an isolation insulating layer so that the first and second fin structures with the protective layer with the reduced height are embedded in the isolation insulating layer;
• removing a part of the upper layer of the first fin structure and the isolation insulating layer, thereby forming an opening in the isolation insulating layer;
• and
• forming a channel layer on the upper layer of the first fin structure in the opening.