We demonstrate the first successful mapping of the two-dimensional electrostatic potential in semiconductor transistor structures by electron holography. Our high resolution 2D phase maps allow the delineation of the source and drain areas in deep submicron transistors. By measuring the mean inner potential of Si and surface depletion effects in thin cross-section samples, we have directly determined the 2D electrostatic potential distribution with 10 nm spatial resolution and 0.1 V sensitivity. We discuss the sensitivity limits of the technique, and outline its possible applications in the study of solid state reactions in two dimensions within a few nanometers of the surface.

• Received 28 August 1998

DOI:https://doi.org/10.1103/PhysRevLett.82.2614