A film stack for forming shallow trench isolation among transistors and other devices on a semiconductor substrate is provided, including a plurality of light absorbing layers alternating between a layer of SiON and a layer of SiO.sub.2 and having a combined extinction coefficient >0.5. As reflected light interacts with the light absorbing layers, a substantial amount of light is absorbed therein thereby blocking such reflected light from negatively interfering with patterning of the photoresist during photo-lithography. Following patterning of the photoresist, isolation trenches may be formed in the semiconductor substrate by etching through the light absorbing layers and into the semiconductor substrate in accordance with the pattern formed on the photoresist.