Gate cut isolation formed as layer against sidewall of dummy gate mandrel

A method, comprising:

• forming a dummy gate material mandrel having a sidewall positioned between and spaced from a first active region covered by the dummy gate material mandrel and a second active region not covered by the dummy gate material mandrel;
• forming a gate cut dielectric layer against the sidewall of the dummy gate material mandrel;
• removing at least one selected portion of the gate cut dielectric layer against the sidewall;
• depositing a dummy gate material over at least the second active region to create a dummy gate material layer with the dummy gate material mandrel, the dummy gate material layer encasing the remaining gate cut dielectric layer;
• forming at least one dummy gate from the dummy gate material layer over the remaining gate cut dielectric layer and over the first and second active region;
• depositing an interlayer dielectric (ILD) about each dummy gate;
• removing each dummy gate to create a gate cut isolation separating space vacated by each dummy gate into a first gate trench over the first active region and a second gate trench over the second active region;
• and
• forming a gate conductor in each gate trench, the gate cut isolation electrically isolating respective first and second portions of the gate conductor.