A structure, for testing relative to an MOS transistor, closely resembles the MOS transistor of interest. For example, certain dimensions and a number of dopant concentrations typically are substantially the same in the test structure as found in corresponding elements of the MOS transistor of interest. However, the regions of the test structure corresponding to the source and drain of the transistor have no halos or extensions that might cause gate overlap; and in the test structure, these regions are of a semiconductor type opposite the type found in the source and drain of the transistor. The test structure enables accurate measurement of the gate-body current, for modeling floating body effects and/or for direct electrical measurement of gate length.