In a method of treating a semiconductor substrate, a plurality of active regions and a plurality of trench isolation regions are formed by selectively etching the semiconductor substrate. The semiconductor substrate is washed by providing deionized water to the semiconductor substrate. A silicon-based solution is provided to the semiconductor substrate by replacing the deionized water disposed on the semiconductor substrate with the silicon-based solution. A silicon oxide material is formed from the silicon-based solution by performing a heat treatment on the silicon-based solution and the semiconductor substrate. The silicon oxide material fills the trench isolation regions.