Embodiments of the present disclosure provide a method of cleaning a lanthanum containing substrate without formation of undesired lanthanum compounds during processing. In one embodiment, the cleaning method includes treating the lanthanum containing substrate with an acidic solution prior to cleaning the lanthanum containing substrate with a HF solution. The cleaning method permits using lanthanum doped high-k dielectric layer to modulate effective work function of the gate stack, thus, improving device performance.