We present both modeling and experimental results devoted to design, fabrication and characterization of metal covered hexagonal diffraction gratings. Variation of exposition and development time allow to modify the shape of the elementary cell, leaving the depth and periodicity unchanged. The fabrication process was modeled using real parameters of the lithography bench and the photoresist, substantially improving experimental results. The high quality of metal covered gratings is confirmed by excitation of plasmonic resonances, which are in a good agreement with theoretical predictions. The described approach allows to better understand plasmonic effects in 2D periodic structures and leads to an optimized design of plasmonic sensors.