Provided is a method of manufacturing a semiconductor device. The method includes forming an underlying structure on a semiconductor substrate, forming a material layer on the semiconductor substrate having the underlying structure, the material layer including a first region having a first surface disposed at a first height from a surface of the semiconductor substrate and a second region having a second surface disposed at a second height lower than the first height, and planarizing the material layer. The planarization of the material layer includes coating an etchant on the material layer disposed on the semiconductor substrate, and selectively heating the first region of the material layer to increase an etch rate of the first region of the material layer more than an etch rate of the second region of the material layer.