A sensor element for determining at least one physical property of a gas in a measuring gas chamber, particularly for determining an oxygen concentration in an exhaust gas. The sensor element includes at least one first electrode and at least one second electrode, and at least one solid electrolyte connecting the first electrode and the second electrode. The second electrode is situated on the inside of the sensor element and is able to have gas from the measuring gas chamber applied to it via at least one gas access hole and at least one diffusion barrier. At least partially gas-impermeable cover layer is provided on the diffusion barrier, at least from area to area. The gas access hole has at least one chamfer in the vicinity of the cover layer.