A hard mask etch stop is formed on the top surface of tall fins to preserve the fin height and protect the top surface of the fin from damage during etching steps of the transistor fabrication process. In an embodiment, the hard mask etch stop is formed using a dual hard mask system, wherein a hard mask etch stop layer is formed over the surface of a substrate, and a second hard mask layer is used to pattern a fin with a hard mask etch stop layer on the top surface of the fin. The second hard mask layer is removed, while the hard mask etch stop layer remains to protect the top surface of the fin during subsequent fabrication steps.