How do low-Vt and high-Vt devices differ specifically in their fabrication processes?

Can someone explain how fabrication processes differ for low-Vt and high-Vt devices? Specifically, what changes are made in doping, gate oxide thickness, or other steps to achieve these variations? Additionally, what are the trade-offs in terms of performance, power, or leakage when choosing between low-Vt and high-Vt devices?