Abstract: This invention includes methods of depositing a silicon dioxide comprising layer in the fabrication of integrated circuitry, and to methods of forming trench isolation in the fabrication of integrated circuitry. In one implementation, a method of depositing a silicon dioxide comprising layer in the fabrication of integrated circuitry includes flowing an aluminum containing organic precursor to a chamber containing a semiconductor substrate effective to deposit an aluminum comprising layer over the substrate. An alkoxysilanol is flowed to the substrate comprising the aluminum comprising layer within the chamber effective to deposit a silicon dioxide comprising layer over the substrate.