Device isolation technology on semiconductor substrate

A method of forming a conformal and/or gap-filling insulative layer on a semiconductor substrate having at least one trench, comprising:

• providing a silicon-containing gas, a nitrogen-containing gas, and a carbon-containing gas as a process gas, said process gas being capable of filling the trench by forming a flowable, insulative material by plasma reaction at first flow rates of the silicon-containing gas, the nitrogen-containing gas, and the carbon-containing gas;
• decreasing a ratio of the first flow rate of the carbon-containing gas to the first flow rate of the silicon-containing gas and/or a ratio of the first flow rate of the carbon-containing gas to the first flow rate of the nitrogen-containing gas;
• forming a conformal/flowable, insulative material by plasma reaction at the decreased flow rate(s), thereby forming a conformal coating in the trench as a result of the step of decreasing the ratio(s);
• and
• multi-step post deposition treatment after the step of forming the conformal/flowable, insulative material, said multi-step post deposition treatment comprising heating the substrate including the conformal coating in the presence of oxygen, irradiating the heated substrate with UV light in the presence of oxygen, and annealing the UV irradiated substrate, thereby removing carbon from the conformal coating as a result of the multi-step post deposition treatment.