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We design a deep-trench microstructure covered with thin gold films to enhance near-infrared absorption of silicon material. This deep-trench microstructure exhibits a much higher absorption compared with plane nanoantenna arrays. We investigate its absorption enhancement in detail and find that the trench-shaped plasmonic waveguide greatly contributes an absorption enhancement by concentrating light effectively. Further, we clarify the influence of both trench depth and gold films covering on different positions of deep trench on the absorption. Finally, we use surface plasmon polaritons offered by plasmonic waveguide to explain well the significant enhancement of near-infrared absorption. [ABSTRACT FROM AUTHOR]