Abstract: A method for forming dielectric filled isolation trenches in a semiconductor substrate wherein the substrate is coated with a photopolymer layer which also fills the trenches. Depending on the type of radiation used, the photopolymer layer is masked except for the regions directly above the filled trenches. The structure is exposed to radiation through the mask, which is then removed. The unexposed portions of the photopolymer layer are washed away and heat is gradually applied to shrink the remaining photopolymer into the trenches until it becomes coplanar with the semiconductor substrate surface. A mask is used if the radiation is ultraviolet light, but no mask is required if electron beam or x-radiation is employed.