Three-dimensional (3D) InAs dots were formed from 2D layers by annealing. Critical thickness (CT) of 2D-3D transition due to annealing was studied, and it was found that this shape transition depends on the growth condition of the 2D InAs layers, which changes the surface structure of the 2D layers. The formation mechanism of the 3D dots was kinetically explained by desorption of indium species from step edges and their aggregation near the steps. (C) 2003 Elsevier Science B.V. All rights reserved.