Silicon germanium and germanium multigate and nanowire structures for logic and multilevel memory applications

1. A method to provide a transistor or memory cell structure comprising:

providing a substrate including a lower Si substrate and an insulating layer on the substrate;

providing a first projection extending above the insulating layer, the first projection including an Si material and a Si1-xGex material on the Si material by growing a Si/Si1-xGex superlattice on the lower Si substrate and creating a Si/Si1-xGex fin from the superlattice;

exposing the first projection to preferential oxidation to yield a second projection including a center region comprising Ge/Si1-yGey and a covering region comprising SiO2 and enclosing the center region, wherein the second projection is a multilevel core structure, the center region including a plurality of center subregions comprising respective floating nanowires, and the covering region including an insulation covering surrounding the nanowires and electrically insulating each of the nanowires.

2. The method of claim 1 , wherein:

the first projection includes a Si fin; and

the Si1-xGex material of the first projection is disposed on three sides of the fin.

3. The method of claim 2 , wherein providing a first projection comprises epitaxially growing the Si1-xGex material on the Si material.

4. The method of claim 2 , wherein:

the center region comprises a Ge/Si1-yGey fin projecting above the insulating layer; and

the method further comprises selectively removing the covering region to expose the Ge/Si1-yGey fin.

5. The method of claim 3 , further comprising growing a Si cap on top of the Si1-xGex material of the first projection to yield a sacrificial protective layer before exposing.

6. The method of claim 1 , further comprising forming source and drain contacts including anchoring a portion of the Si fin on both ends thereof prior to exposing.