Preparing a semiconductor alloy channel by generating a hard mask layer stack and applying a plasma assisted mask patterning process

A method comprising: Forming a first hard mask layer (214) on a first active region (202A) and a second active region (202B) of a semiconductor device; Forming isolation regions (202C), which limit the first active region and the second active region laterally, after forming the first hard mask layer; Forming a second hard mask layer (204) on the first hard mask layer after formation of the isolation regions; thereafter forming an etching mask in such a way (205) so as to cover the first and second hard mask layer over the second active region and leaves open above the first active region; Removing the first and the second hard mask layer selectively from the first active region by performing a plasma-assisted etch process, the second hard mask layer remains on the second active region; thereafter removing the etching mask; Forming a layer of a semiconductor alloy (208) on the first active region and using the first and / or second hard mask layer on the second active region as a growth mask; Exposing said second active region; and Forming a first gate electrode structure of a first transistor on the layer of a semiconductor alloy and a second gate electrode structure of a second transistor on the second active region, wherein the first and the second gate electrode structure having a metal-containing gate electrode material and gate insulation layer with a dielectric material having a large e.