A large number of applications of electron-beam lithography (EBL) systems in nanotechnology have been demonstrated in recent years. In this paper we present a simple and general-purpose EBL system constructed by insertion of an electrostatic deflector plate system at the electron-beam exit of the column of a scanning electron microscope (SEM). The system can easily be mounted on most standard SEM systems. The tested setup allows an area of up to about 50 x 50 microm to be scanned, if the upper limit for acceptable reduction of the SEM resolution is set to 10 nm. We demonstrate how the EBL system can be used to write three-dimensional nanostructures by electron-beam deposition.