Method of forming finned semiconductor devices with trench isolation

1. A trench isolation method for finned semiconductor devices, the method comprising:

forming, from a bulk semiconductor substrate, a first conductive fin set and a second conductive fin set, the first conductive fin set and the second conductive fin set being separated by a gap;

depositing an oxide material over the first conductive fin set, the second conductive fin set, and the bulk semiconductor substrate, the oxide material forming a recess that corresponds to the gap, the recess being defined by opposing sidewalls of the oxide material;

deepening the recess into the bulk semiconductor substrate to form a trench that is self-aligned with the opposing sidewalls;

filling the trench with a dielectric material, and filling between adjacent conductive fins in the first conductive fin set and between adjacent conductive fins in the second conductive fin set with the dielectric material; and

etching a portion of the dielectric material to expose an upper section of the first conductive fin set and an upper section of the second conductive fin set, while preserving the dielectric material in the trench, and retaining a layer of the dielectric material between and at the base of the adjacent conductive fins in each conductive fin set.

2. The method of claim 1 , wherein the forming step forms a plurality of conductive fins in the first conductive fin set, and a plurality of conductive fins in the second conductive fin set.

3. The method of claim 2 , wherein the forming step forms the plurality of conductive fins in the first conductive fin set and the plurality of conductive fins in the second conductive fin set in accordance with a designated fin pitch, and such that the gap separates the first conductive fin set from the second conductive fin set by a distance greater than the designated fin pitch.

4. The method of claim 1 , wherein deepening the recess comprises:

etching the oxide material to extend the recess to the bulk semiconductor substrate; and

thereafter etching the bulk semiconductor substrate using the oxide material as an etch mask.

5. The method of claim 1 , wherein filling the trench comprises depositing an oxide in the trench, over the bulk semiconductor substrate, over the first conductive fin set, and over the second conductive fin set.

6. The method of claim 5 , further comprising polishing the oxide to a height of the first conductive fin set and the second conductive fin set.

7. The method of claim 6 , further comprising etching the oxide to expose only a portion of the first conductive fin set and to expose only a portion of the second conductive fin set.

8. The method of claim 1 , further comprising:

completing fabrication of a first device structure that includes the first conductive fin set; and

completing fabrication of a second device structure that includes the second conductive fin set; wherein

the dielectric material in the trench electrically isolates the first device structure from the second device structure.

9. The method of claim 8 , wherein:

the first device structure is an NMOS transistor device structure that includes the first conductive fin set; and

the second device structure is a PMOS transistor device structure that includes the second conductive fin set.

10. The method of claim 1 , further comprising:

forming, from the oxide material, spacers in the gap and adjacent a first conductive fin structure in the first conductive fin set and adjacent a second conductive fin structure in the second conductive fin set; and

etching the bulk semiconductor substrate, using the spacers as an etch mask, to form the trench in the bulk semiconductor material.

11. The method of claim 10 , wherein etching the bulk semiconductor material forms the trench such that it is self-aligned with the spacers.