A method of forming a shallow trench isolation (STI) for an integrated circuit (IC) structure to mitigate fin bending disclosed. The method may include forming a first insulator layer in a first portion of an opening in a substrate by a bottom-up atomic layer deposition (ALD) process; and forming a second insulator layer on the first insulator layer in a second portion of the opening. The opening may be position between a set of fins in the substrate. The method may further include forming an oxide liner in the opening before the forming the first insulator layer. The second insulator layer may be formed by deposition using a flowable chemical vapor deposition (FCVD) process, high aspect ratio process (HARP), high-density plasma chemical vapor deposition (HDP CVD) process, or any other conventional insulator material deposition process.