Electronic defect states at material interfaces provide highly deleterious sources of noise in solid-state nanostructures, and even a single trapped charge can qualitatively alter the properties of short one-dimensional nanowire field-effect transistors (FET) and quantum bit (qubit) devices(1-5). 'Understanding the dynamics of trapped charge is thus essential for future nanotechnologies, but their direct detection and manipulation is rather challenging(2,4,5). Here, a transistor-based set-up is used to create and probe individual electronic defect states that can be coherently driven with microwave (MW) pulses. Strikingly, we resolve a large number of very high quality (Q similar to 1 x 10(5)) resonances in the transistor current as a function of MW frequency and demonstrate both long decoherence times (similar to 1 mu s-40 mu s) and coherent control of the defect-induced dynamics. Efficiently characterizing over 800 individually addressable resonances across two separate defect-hosting materials, we propose that their properties are consistent with weakly driven two-level systems.