Methods for threshold voltage tuning and structures formed thereby

A structure comprising:

• a first transistor on a substrate, the first transistor comprising:
• a first gate dielectric layer over a first active area, the first gate dielectric layer being doped with a dipole dopant species at a first dipole dopant concentration;
• and
• a first gate over the first gate dielectric layer;
• and
• a second transistor on the substrate, the second transistor comprising:
• a second gate dielectric layer over a second active area, the second gate dielectric layer being doped with a dipole dopant species at a second dipole dopant concentration, the first dipole dopant concentration being greater than the second dipole dopant concentration;
• and
• a second gate over the second gate dielectric layer.

A method for semiconductor processing, the method comprising:

• forming a gate dielectric layer over a first active area and a second active area, the first active area and the second active area being on a substrate;
• forming a first dipole layer over the gate dielectric layer over the first active area;
• and
• diffusing a dipole dopant species from the first dipole layer into the gate dielectric layer, wherein after diffusing the dipole dopant species from the first dipole layer into the gate dielectric layer, a dipole dopant concentration in the gate dielectric layer over the first active area is greater than a dipole dopant concentration in the gate dielectric layer over the second active area.