The present invention discloses a method for manufacturing a semiconductor device, comprising the steps of: forming a dummy gate stack structure on a substrate, wherein the dummy gate stack structure contains carbon-based materials; forming source/drain region in the substrate on both sides of the dummy gate stack structure; performing etching to remove the dummy gate stack structure until the substrate is exposed, resulting in a gate trench; and forming a gate stack structure in the gate trench. In accordance with the method for manufacturing a semiconductor device of the present invention, the dummy gate made of carbon-based materials is used to substitute the dummy gate made of silicon-based materials, then no oxide liner and/or etch blocking layer needs be added while the dummy gate is removed by etching in the gate last process, thus the reliability of device is ensured while the process is simplified and the cost is reduced.