The present invention provides a nanometer-scale transistor architecture providing enhanced carrier mobility. In particular, a portion of a channel of a transistor is substantially surrounded with an acoustically hard material to form a barrier shell about the channel. The barrier shell functions to confine phonons in the channel. Confining the phonons in the channel reduces the extent to which atoms in the crystal lattice structure of the channel move as they vibrate. Restricting the extent that the atoms vibrate in the crystal lattice of the channel significantly reduces the scattering of electrons or holes traveling through the channel. In one embodiment of the invention, the thickness of the channel is in the order of the thermal phonon wavelength of the material forming the channel, and the barrier shell is acoustically harder than the channel. The benefits of the present invention may be provided without requiring strain engineering.