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A grayscale technology process for structuring of true 3D shapes into crystalline silicon (c-Si) has been developed. The process combines maskless grayscale lithography and an optimized RIE process. To achieve a 1:1 transfer of the 3D photoresist patterns into c-Si, the RIE process was optimized for a selectivity of S = 1 and an anisotropy A_f close to one. Suitable process conditions of the RIE process are defined by SF₆ flowrate of 3 sccm, CHF₃ flowrate of 35 sccm, a RF power of 100 W, a temperature of 10 °C and a pressure of 10 mTorr. The 3D pattern transfer is demonstrated at special test structures as well as at real 3D structures such as pyramids. The developed process allows a direct transfer from 3D CAD data via maskless grayscale lithography using Heidelberg Instrument DWL66FS to c-Si 3D structures. The pattern transfer accuracy is about 5% in respect to the 3D CAD data.