We present results of a numerical formalism developed to address the band structure and charge control problem in n- and p-type silicon and silicon-germanium metal-oxide-semiconductor field effect transistors. We focus on the following issues: (i) the dependence of the in-plane carrier effective mass on sheet charge density and germanium content; (ii) the fraction of charge near the interface and the evaluation of the interface roughness matrix element. Results are compared to existing models. For n-type structure, the effective mass approximation and deformation potential theory is used to describe the electron states. However, for p-type structure, a six-band k∙p Kohn–Luttinger formulation is used to describe the hole states due to the strong coupling of heavy-hole, light-hole, and split-off bands. This allows us to examine the influence of the coupling of the heavy-hole, light-hole, and the split-off bands. © 1998 American Institute of Physics.