Method for manufacturing semiconductor devices

A method for manufacturing a semiconductor device, wherein the semiconductor device has a first region and a second region, the method comprising:

• forming a first fin structure and a second fin structure on a substrate, wherein the first fin structure and the second fin structure are in the first region and the second region respectively;
• forming a first stack structure and a second stack structure so as to respectively cover a portion of the first fin structure and of the second fin structure, wherein the first stack structure and the second stack structure respectively include a dummy layer and a hard mask layer from bottom to top;
• forming a spacer respectively on sidewalls of the first fin structure and of the second fin structure through an atomic layer deposition process, wherein a composition of the spacers includes silicon carbon nitride;
• forming an interlayer dielectric covering the first stack structure, the second stack structure and the spacers;
• etching the interlayer dielectric so as to expose each of the hard mask layers;
• forming a mask layer to cover the second stack structure and a portion of the dielectric layer;
• removing the hard mask layer in the first stack structure under a coverage of the mask layer;
• removing the dummy layer in the first stack structure to leave a first trench;
• and
• filling up the first trench with a conductive layer.