We describe fabrication methods of GaAs and InAs quantum dot (QD) structures and related semiconductor nanostructures having nanoscale heterointerfaces grown by the selective area metalorganic vapor-phase epitaxial (SA-MOVPE) method on partially masked GaAs substrates. GaAs QD arrays and wire-dot coupled structures having strong lateral confinement were fabricated on appropriately designed masked substrates. InAs QDs were also formed on various kinds of GaAs pyramidal and wire structures, where site-selective formation is demonstrated by the combination of self-assembling growth mode and selective area growth. The application of QDs to single-electron transistors using SA-MOVPE is also described. (C) 2002 Elsevier Science B.V. All rights reserved.