We have fabricated a nanometer-scale transistor that operates by using a gate field to modulate the transmission of electrons through a lateral metal/oxide tunnel barrier. Our initial devices have a 30-nm-wide lateralNb/NbOxtunnel junction on top of a planarAl2O3/Alburied gate. We observe effective modulation of the source–drain current with gate bias at room temperature with negligible gate leakage current. We identify the materials issues that currently limit the device performance, and we offer direction for future device improvements.