A method for depositing silicon oxide layers having a low dielectric constant by reaction of an organosilicon compound and a hydroxyl forming compound at a substrate temperature less than about 400° C. The low dielectric constant films contain residual carbon and are useful for gap fill layers, pre-metal dielectric layers, inter-metal dielectric layers, and shallow trench isolation dielectric layers in sub-micron devices. The hydroxyl compound can be prepared prior to deposition from water or an organic compound. The silicon oxide layers are preferably deposited at a substrate temperature less than about 40° C. onto a liner layer produced from the organosilicon compound to provide gap fill layers having a dielectric constant less than about 3.0.