Methods of forming a semiconductor device are provided. An active region is formed on a substrate. A temporary gate crossing the active region and a capping pattern covering the temporary gate are formed. Spacers are formed on sidewalls of the temporary gate. A growth-blocking layer is locally formed in an upper edge of the temporary gate. A source/drain region is formed on the active region adjacent to the temporary gate. The capping pattern, the first growth-blocking layer, and the temporary gate are removed to expose the active region. A gate electrode is formed on the exposed active region.