The present invention presents a method for manufacturing a semiconductor device structure as well as the semiconductor device structure. Said method comprises: providing a semiconductor substrate; forming a first insulating layer on the semiconductor substrate; forming a shallow trench isolation embedded in the first insulating layer and the semiconductor substrate; forming a channel region embedded in the semiconductor substrate; and forming a gate stack stripe on the channel region. Said method further comprises, before forming the channel region, performing a source/drain implantation on the semiconductor substrate. By means of forming the source/drain regions in a self-aligned manner before forming the channel region and the gate stack, said method achieves the advantageous effects of the replacement gate process without using a dummy gate, thereby simplifying the process and reducing the cost.