METHOD OF FORMING SHALLOW TRENCH ISOLATION (STI) STRUCTURES

A method of forming a trench isolation (e.g., an STI) for an integrated circuit includes forming a pad oxide layer and then a nitride layer over a semiconductor substrate, performing a trench etch through the structure to form a trench, depositing a trench oxide layer over the structure to form a filled trench, depositing a sacrificial planarizing layer, which is etch-selective to the trench oxide layer, over the deposited oxide, performing a planarizing etch process that removes the sacrificial planarizing layer and decreases surface variations in an upper surface of the trench oxide layer, performing an oxide etch process that is selective to the trench oxide layer to remove remaining portions of the trench oxide layer outside the filled trench, and removing the remaining nitride layer such that the remaining oxide-filled trench defines a trench isolation structure that projects above an exposed upper surface of the semiconductor substrate.