Fin Structure of Semiconductor Device

A method of fabricating a semiconductor device, comprising:

• forming a fin structure including a lower portion of a first material and an upper portion of a second material and an interface between the first material and the second material;
• forming an isolation structure surrounding the lower portion, wherein the interface and the upper portion extend above an topmost surface of the isolation structure;
• and
• selectively oxidizing portions of the fin structure to form a first ring extending into the lower portion from sidewalls of the fin structure at a point of contact between the lower portion and the topmost surface of the isolation structure, and to form a second ring extending into the fin structure from the sidewalls of the fin structure at the interface.

A method of fabricating a semiconductor device comprising:

• forming a pad layer over a semiconductor substrate and a hard mask layer over the pad layer;
• patterning the pad layer and the mask layer;
• patterning the semiconductor substrate to form a first fin and a second fin extending from the semiconductor substrate and a trench between the first fin and the second fin;
• depositing a dielectric material to surround the first fin and the second fin;
• planarizing the first fin, the second fin and the dielectric material;
• recessing a top surface of the first fin and of the second fin to form a first lower fin portion with a first cavity thereabove and a second lower fin portion with a second cavity thereabove;
• filling the first cavity with a first upper fin portion forming a first interface with the first lower fin portion to form a first fin structure, and filling the second cavity with a second upper fin portion forming a second interface with the second lower fin portion to form a second fin structure;
• recessing the dielectric material to have a topmost surface at a level below the first interface and the second interface;
• and
• forming a first oxide ring extending into the first fin structure, and forming a second oxide ring extending into the first fin structure at the first interface;
• and
• forming a third oxide ring extending into the second fin structure, and forming a fourth oxide ring extending into the second fin structure at the second interface.