The present invention discloses a method for manufacturing semiconductor device, including: forming device isolation structure on a semiconductor substrate to limit an active area; forming a hard maskpattern to limit a concave area on the semiconductor substrate; etching the semiconductor substrate selectively using the hard mask pattern as etching mask, so as to form concave type channel structure, the etching process is completed by two plasma etching methods under different etching conditions; removing the hard mask pattern to bare the semiconductor substrate containing the concave type channel structure; and forming a grid electrode to fill the concave type channel structure.