The shallow trench isolation (STI) module provides critical electrical and structural isolation between adjacent active regions, suppressing parasitic conduction and leakage currents P3.Following the initial trench etch and thermal STI liner oxidation—which repairs plasma damage and rounds trench corners to prevent stress concentration and field enhancement P3—the STI Fill Conformal CVD Liner step is executed.This deposition step introduces a thin, highly conformal dielectric layer over the ther