A semiconductor device and method for manufacturing the same are disclosed. The method comprises: forming a gate insulating layer and a gate above a substrate; forming a spacer on both sides of the gate respectively; etching the substrate with the gate and spacers as mask to form indents; respectively forming a dummy sidewall on the side of the spacers opposite to the gate; etching substrate with the gate, spacers and dummy sidewalls as mask to form recesses which are deeper than the indents; removing the dummy sidewalls; and filling SiGe in the indents and recesses to form source/drain extent regions and source/drain regions of the semiconductor device; wherein before the step of filling SiGe, a step of heating the substrate to reflow the substrate material so as to at least change the shape of the side surface of the indent on the side close to the gate is implemented.