A semiconductor device, which is characterized by that two or more island-shaped semiconductor layers including first and second island-shaped semiconductor layers are formed on the same substrate, at least the first island-shaped semiconductor layer has steps in its side wall so that sectional area of a cross section parallel to the surface of the substrate varies stepwise with respect to height in the vertical direction, the second island-shaped semiconductor layer is different from the first island-shaped semiconductor layer with respect to the presence/absence of a step in the side wall or the number of steps, and each of the first and second island-shaped semiconductor layers provides an element on a stair part of the side wall divided by the steps or on the side wall having no steps.