Method for fabricating a semiconductor device including gate-to-bulk substrate isolation

A method for fabricating a semiconductor device, the method comprising:

• forming a sacrificial layer of a first semiconductor material on a substrate;
• forming a layer of a second semiconductor material on the sacrificial layer;
• forming a layer of a third semiconductor material on the layer of the second semiconductor material;
• removing portions of the layer of the third semiconductor material, portions of the second semiconductor material, and portions of the sacrificial layer to form a sacrificial fin in the sacrificial layer, a first nanowire arranged on the sacrificial fin and a second nanowire arranged on the first nanowire;
• depositing a layer of insulator material in trenches defined by the sacrificial layer adjacent to the sacrificial fin;
• etching to remove exposed portions of the first nanowire;
• and
• performing an oxidizing process that forms a first layer of oxide material on exposed portions of the second nanowire and a second layer of oxide material on exposed portions of the sacrificial fin, the first layer of oxide material having a first thickness and the second layer of oxide material having a second thickness, where the first thickness is less than the second thickness.

A semiconductor device comprising:

• a substrate;
• a fin arranged on the substrate;
• a layer of oxide material arranged on the fin;
• a nanowire comprising a semiconductor material arranged over the layer of oxide material where the layer of oxide material is disposed between the fin and the nanowire;
• and
• a gate stack arranged around the nanowire and over the layer of oxide material.