Dummy dielectric fins for finFETs with silicon and silicon germanium channels

A method for forming a semiconductor device, comprising:

• etching a portion of a semiconductor substrate, the substrate including a first semiconductor material;
• growing a second semiconductor material in a trench formed by removing the portion of the semiconductor substrate, wherein the first semiconductor material is different from the second semiconductor material;
• etching first fins in the first semiconductor material and second fins in the second semiconductor material in accordance with a dielectric mask;
• forming spacers on sidewalls of the dielectric mask and the first fins and the second fins thus encapsulating the first fins and the second fins with a protective dielectric;
• etching semiconductor material between the first fins and the second fins thus forming trenches;
• filling the trenches, between the first fins and between the second fins with a dielectric fill;
• oxidizing the first semiconductor material below the first fins and the second semiconductor material below the second fins while the first and second fins are encapsulated by the protective dielectric;
• and
• oxidizing fins in an intermediary region between the first fins and the second fins thus forming consecutive dummy fins in the intermediary region, the dummy fins stripped of the protective dielectric, to create a uniform topology of all first fins, second fins, and dummy fins with same heights across the device.