A method of forming patterns, patterns formed according to the method, and a semiconductor device including the patterns, the method including forming an etching subject layer on a substrate, forming a first layer on the etching subject layer such that the first layer has a projecting pattern, forming a second layer such that the second layer completely covers the projecting pattern of the first layer, partially removing the second layer such that a top of the projecting pattern is exposed and a patterned second layer remains at a side of the projecting pattern, removing the first layer such that a top of the etching subject layer is exposed, and etching the etching subject layer using the patterned second layer as an etching mask, wherein one of the first layer and the second layer is a carbon-containing layer and the other is a silicon-containing layer, and the silicon-containing layer is formed by coating a silicon-containing composition and heat-treating the same.