Terahertz biosensors are used for sensing chemical and biochemical material. In order to sense small material quantities, such as DNA strands, sensors with a high sensitivity are needed. Our recent approach applies asymmetric double-split ring resonators (aDSR) in a two-dimensional array. Interaction of resonances within the structure results in a steep flank in the frequency response which is sensitively shifted by small amounts of biomolecules loaded on the sensor surface. Additionally a high E-field concentration connected to the split ring resonances is used to maximize the frequency shift induced by biomaterial covering only a small fraction of the sensor area. Minutes amounts of biomaterial can therefore be detected. In this presentation, the approach is analyzed with numerical simulation. We demonstrate the functionality and optimization of the aDSR array structures, and the capability to detect submicrometer layers of dielectric material with a spatially selective deposition on the resonant structures. A measurement of the complementary structure is presented as proof of principle.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.