I've been watching professor Lundstrom's ECE 656: Electronic Transport in Semiconductors (Fall 2011) lectures on the nanoHUB, which are extremely good. As result, I started to reading his book Fundamentals of Carrier Transport. Quantum confinement is common in many devices today and even in silicon MOSFETs. Professor Lundstrom makes the following analogy about the nature of the confined electrons that I have not seen anywhere else, but find very helpful (see page 39).

The wave functions of confined electrons are qualitatively different from the plane waves that describe three-dimensional bulk electrons. There is a close analogy between confined electrons and electromagnetic waves in a waveguide. The various subbands are analogous to waveguide modes; occupied subbands correspond to propagating modes, unoccupied subbands to evanescent modes. This analogy can even be exploited to build electron devices analogous to optical or microwave devices.