Semiconductor Device and Fabricating the Same

A semiconductor device comprising:

• a substrate having an N-type field-effect transistor (N-FET) region;
• a gate region in the N-FET region;
• source and drain regions separated by the gate region in the N-FET region;
• a first fin structure in a gate region in the N-FET region, the first fin structure including:
• a silicon germanium (SiGex) layer as a lower portion, where x is Ge composition in atomic percent;
• a silicon germanium oxide (SiGeOy) layer as a middle, where y is oxygen composition in atomic percent;
• and
• a Si layer as an upper portion;
• a second fin structure in S/D regions in the N-FET region, the second fin structure including;
• the SiGex layer as a lower portion;
• the SiGeOy as a first middle portion, wherein it directly contacting the middle portion of the first fin in the gate region;
• the SiGex as a second middle portion beside the first middle;
• and
• the Si layer as an upper portion;
• source/drain features on top of the upper portion of the second fin structure in the source and drain regions;
• and
• a high-k/metal gate (HKMG) on the substrate including wrapping over a portion of the first fin structure.

A semiconductor device comprising:

• a first fin structure including:
• a first semiconductor material layer as a lower portion of the first fin structure, a semiconductor oxide layer as a middle portion of the first fin structure, and a second semiconductor material layer as an upper portion of the first fin structure;
• and
• a second fin structure including:
• the first semiconductor material layer as a lower portion of the second fin structure, the semiconductor oxide layer as a first middle portion of the second fin structure, the first semiconductor material layer as a second middle portion beside the first middle portion of the second fin structure, and the second semiconductor material layer as an upper portion of the second fin structure.