Effective work function instability of high‐κ∕metal gate MOS stacks after high temperature treatment results in device threshold voltage shifts and is one of the problems associated with the gate‐first integration of high‐κ dielectrics in the CMOS process flow. The exact reason for this instability is subject of intense debate. In this paper it is shown that a positive threshold voltage shift due to thermal treatment can be compensated by implanting the lanthanoids lanthanum or dysprosium into the high‐κ stack
