Volumeless threshold voltage tuning for stacked device structures

Abstract

Dipole engineering techniques for stacked device structures are disclosed herein. According to various aspects of the present disclosure, an exemplary dipole engineering technique includes (1) forming at least two patterned dipole dopant source layers having different patterns and covering gate dielectric layers of some transistors, but not other transistors, (2) performing a thermal drive-in process (e.g., a dipole drive-in anneal), and (3) after removing the dipole dopant source layer, forming gate electrodes for the transistors, where a same gate electrode material is used for the transistors. Thickness(es) and/or material characteristics (e.g., dipole dopant) of the patterned dipole dopant source layers and/or parameters of the thermal drive-in process may be configured to achieve desired threshold voltages. Such technique may provide 2threshold voltages (Vt), where N is a number of patterned dipole dopant source layers formed on the gate dielectric layers of the transistors to tune their threshold voltages.