Maximizing performance for higher K gate dielectrics

Further scaling of complementary metal oxide semiconductor gate stacks will require gate dielectrics with a higher dielectric constant (K) than HfO2. We point out that this will require strategies to minimize the overall effective oxide thickness of the gate stack, and not just maximizing the dielectric constant, so that the channel mobility is not impaired and there is still control of the flatband voltages. This may require retention of a SiO2-based interfacial layer, and attention should be paid to the flatband voltages of lanthanide oxides. Phase control of HfO2 and ZrO2 by addition of group IV elements offers simpler advances.