Fin end isolation structure for semiconductor devices

A semiconductor structure, comprising:

• a substrate;
• first and second semiconductor fins extending from the substrate, wherein the first and the second semiconductor fins are lengthwise aligned along a first direction, and a first end of the first semiconductor fin faces a second end of the second semiconductor fin;
• a first isolation structure over the substrate and adjacent to sidewalls of the first and the second semiconductor fins;
• first and second gate structures that are oriented lengthwise along a second direction generally perpendicular to the first direction, wherein the first and the second gate structures are disposed over the first isolation structure, the first gate structure is disposed over the first semiconductor fin, and the second gate structure is disposed over the second semiconductor fin;
• and
• a second isolation structure extending from the first end of the first semiconductor fin to the second end of the second semiconductor fin, wherein the first and the second isolation structures include different dielectric materials.

A method, comprising:

• providing a structure having a substrate, a semiconductor fin extending from the substrate, an isolation structure over the substrate and adjacent to sidewalls of the semiconductor fin, and two gate structures over the isolation structure and over the semiconductor fin, wherein a segment of the semiconductor fin is disposed between the two gate structures;
• forming an etch mask that exposes the segment of the semiconductor fin and portions of the isolation structure and the two gate structures that are adjacent to the segment of the semiconductor fin;
• etching the segment of the semiconductor fin through the etch mask to form a first trench;
• forming a spacer layer on sidewalls of the two gate structures and within the first trench;
• and
• forming an inter-layer dielectric (ILD) layer over the gate structures and over the spacer layer, wherein a portion of the ILD layer is within the first trench.