A fabricating method of a semiconductor device includes providing a substrate having a first region and a second region, forming a plurality of first gates in the first region of the substrate, such that the first gates are spaced apart from each other at a first pitch, forming a plurality of second gates in the second region of the substrate, such that the second gates are spaced apart from each other at a second pitch different from the first pitch, implanting an etch rate adjusting dopant into the second region to form implanted regions, while blocking the first region, forming a first trench by etching the first region between the plurality of first gates, and forming a second trench by etching the second region between the plurality of second gates.