We report an approach to the lateral confinement of electrons in InAs/AlSb single quantum wells. Using electron-beam lithography and reactive ion etching, we have fabricated conducting wires, rings, and dots with lateral dimensions greater than or equal to 50 nm. Characterization on narrow wires and rings indicates that the electron transport is in the quasiballistic regime at 4.2 K. The current-voltage characteristics of 70-nm-diam dots in single-electron transistor structures show the Coulomb gap and the Coulomb staircase features. These artificially patterned devices have an ultimate lateral dimension of a few nanometers, limited by the resolution of electron-beam lithography.