** Next:** 4.1 Unprimed Subbands
**Up:** Dissertation T. Windbacher
** Previous:** 3.5.2 The k.p Method

Multi-Gate FinFETs and Ultra Thin Body Silicon On Insulator (UTBSOI) FETs are considered as perfect candidates for the
technology node and beyond.
Strong size quantization leads to a formation of quasi-two-dimensional subbands in carrier systems in thin silicon films. For analytical hole subband structure calculations a six-band **k****.****p** Hamiltonian is commonly employed. The electron subband structure consists of six equivalent minima located close to the X-points in the Brillouin zone. Close to the minimum the energy dispersion is usually described by a parabolic approximation with the transversal masses
and the longitudinal mass
. Isotropic non-parabolicity takes into account deviations in the density of states at higher energies. A more general description is, however, needed in ultra-thin silicon films, especially in the presence of shear strain [178]. The two-band **k****.****p** Hamiltonian accurately describes the bulk structure up to energies of
[179]. It includes a shear strain component which is neglected in the parabolic approximation [161,170,179]. Shear strain is responsible for effective mass modification and is, therefore, an important source of the electron mobility enhancement in ultra-thin silicon films [180,178].

**Subsections**

** Next:** 4.1 Unprimed Subbands
**Up:** Dissertation T. Windbacher
** Previous:** 3.5.2 The k.p Method

T. Windbacher: Engineering Gate Stacks for Field-Effect Transistors