Methods for fabricating integrated circuits

A method for fabricating an integrated circuit comprising:

• forming a first layer of a first semiconductor material overlying a bulk semiconductor substrate that is formed of a second semiconductor material;
• forming a second layer of a third semiconductor material overlying the first layer;
• etching a first plurality of trenches through the first and second layers into the bulk semiconductor substrate;
• filling the first plurality of trenches with a structure forming material to form a plurality of support structures extending from the bulk semiconductor substrate through the first and second layers;
• etching a second plurality of trenches through the first and second layers into the bulk semiconductor substrate, wherein the second plurality of trenches are arranged alternately with the first plurality of trenches, and wherein portions of the second layer disposed between adjacent trenches of the first and second plurality of trenches define a plurality of fins;
• etching the first layer to form gap spaces between the bulk semiconductor substrate and the plurality of fins, wherein the plurality of fins are supported in position adjacent to the gap spaces by the plurality of support structures;
• and
• filling the gap spaces with an insulating material.

A method for fabricating an integrated circuits comprising:

• epitaxially growing a first layer of silicon germanium overlying a bulk silicon substrate;
• epitaxially growing a second layer of silicon overlying the first layer;
• etching a first plurality of trenches through the first and second layers into the bulk silicon substrate;
• filling the first plurality of trenches with a first oxide material to form a plurality of support structures extending from the bulk silicon substrate through the first and second layers;
• etching a second plurality of trenches through the first and second layers into the bulk silicon substrate, wherein the second plurality of trenches are arranged alternately with the first plurality of trenches, and wherein portions of the second layer disposed between adjacent trenches of the first and second plurality of trenches define a plurality of fins;
• etching the first layer to form gap spaces between the bulk silicon substrate and the plurality of fins, wherein the plurality of fins are supported in position adjacent to the gap spaces by the plurality of support structures;
• and
• filling the gap spaces with a second oxide material.