Next, a first cleaning process is conducted to remove the oxide layer remained on the surface of the fin-shaped structures 14 according to step 104. Specifically, as shown in FIG. 4, the first cleaning process conducted at this stage preferably removes the oxide layer formed during the step 103, transforms the angles included between sidewalls of the fin-shaped structures 14 and the top surface of the substrate 12 from angles made of planar surfaces to angles made of curved surfaces, and at the same time removes majority of impurities remained on the surface of the substrate 12 and/or fin-shaped structures 14. In this embodiment, the cleaning agent used in the first cleaning process preferably includes but not limited to for example diluted hydrofluoric acid (dHF).

Next, a second cleaning process is conducted according to step 105 to remove polymers remained on surface of the fin-shaped structures. In this embodiment, the cleaning agent used in the second cleaning process preferably includes but not limited to for example ozone (O₃).

Next, a third cleaning process is conducted according to step 106 to remove particles remained on the surface of the fin-shaped structures. In this embodiment, the cleaning agent used in the third cleaning process preferably includes but not limited to for example Standard Clean 1 (SC1).