A method for fabricating semiconductor device includes the steps of: providing a substrate having a memory region and a periphery region; forming a first buried gate and a second buried gate in the substrate on the memory region; forming a first silicon layer on the substrate on the periphery region; forming a stacked layer on the first silicon layer; forming an epitaxial layer on the substrate between the first buried gate and the second buried gate; and forming a second silicon layer on the epitaxial layer on the memory region and the stacked layer on the periphery region.