In semiconductor surface research, the scanning tunneling microscope (STM) has been applied primarily to the study of the structural and electronic on figurations of elemental group IV surfaces on the atomic scale. Several investigations are reported on semiconductor compound substrates such as GaAs and adsorbates. The interest in epitaxially grown layers is growing, both on the growth plane and in cross sections. This survey will review essentials of elemental surfaces and then focus on growth-related STM work, notably epitaxy and cross sections of III-V compound multilayers. Examples of p-n junctions, interfacial regions and electronic structure across interfaces will be discussed, and a comparison with other spectroscopic and electron-microscopic techniques will be made.