Selectively grown self-aligned fins for deep isolation integration

A method of forming a semiconductor structure, said method comprising:

• providing a structure including a hard mask material stack comprising from bottom to top, an oxide hard mask layer and a nitride hard mask layer on a topmost surface of a semiconductor substrate;
• forming an opening entirely through said hard mask material stack and partially through said semiconductor substrate;
• providing a trench isolation structure in said opening, wherein said trench isolation structure has a topmost surface that is coplanar with a topmost surface of remaining portions of said nitride hard mask layer;
• removing said remaining portion of said nitride hard mask layer to expose remaining portions of said oxide hard mask layer;
• forming a screen oxide layer on each of said remaining portions of said oxide hard mask layer and said topmost surface of said trench isolation structure;
• forming a mandrel structure on said screen oxide layer and having a first portion located above said semiconductor substrate and a second portion located above said trench isolation structure, wherein a bottommost surface of said mandrel structure straddles a sidewall edge of said trench isolation structure;
• forming a nitride spacer on each sidewall of said mandrel structure;
• removing said mandrel structure selective to said nitride spacers;
• forming a dielectric oxide material having a topmost surface that is coplanar with a topmost surface of said nitride spacers;
• removing one of nitride spacers to provide a cavity exposing a portion of said screen oxide layer located above said topmost surface of said semiconductor substrate and another of said nitride spacers to provide another cavity exposing another portion of said screen oxide layer located above said topmost surface of said trench isolation structure;
• extending said cavity to expose said topmost surface of said semiconductor substrate, and said another cavity to expose said topmost surface of said trench isolation structure;
• and
• epitaxially growing a semiconductor fin in said cavity that exposes said portion of said topmost surface of said semiconductor substrate, but not in said another cavity that exposes said portion of said topmost surface of said trench isolation structure.