Finfet structures having silicon germanium and silicon channels

A method comprising:

• obtaining a structure comprising a semiconductor substrate having a top surface, one or more trenches within the semiconductor substrate, one or more silicon germanium regions within the one or more trenches, each of the one or more silicon germanium regions including a top surface coplanar with the top surface of the semiconductor substrate, a plurality of mandrel portions on the top surface of the substrate, the mandrel portions having sidewalls, and a plurality of spacers on the sidewalls of the mandrel portions, and
• forming one or more semiconductor fins from the semiconductor substrate and one or more silicon germanium fins parallel to the one or more semiconductor fins from the one or more silicon germanium regions using sidewall image transfer.

A structure comprising:

• a substrate comprised of crystalline silicon, the substrate including a body portion and one or more first fins comprised of crystalline silicon extending from and integral with the body portion, and
• one or more second fins comprising silicon germanium and integral with the body portion of the substrate, the one or more second fins being parallel to the one or more first fins, at least one of the one or more second fins being within less than 30 nm of at least one of the one or more first fins.