The combination of silicon-on-insulator (SOI) substrates with ultrathin Si and insulator layers opens new opportunities for quantum effect and hot-electron devices. Unlike their III-V predecessors, these devices have the crucial advantage of potential integrability with dominant silicon technology. We discuss three examples of such SOI devices: a three-terminal real-space transfer transistor with a low-barrier dielectric; a vertical tunneling transistor with an ultrathin tunneling gate oxide; and a lateral interband tunneling transistor. None of these devices has progressed beyond a rudimentary proof-of-concept demonstration, but the strong nonlinearities of their characteristics deriving from quantum tunneling or hot-electron injection, as well as their unique scaling behavior, make them an interesting playground for innovative device research. (C) 2004 Elsevier Ltd. All rights reserved.