Metamaterials are artificially structured media that are engineered for electromagnetic properties such as negative refractive index,giant optical activity and circular dichroism.Applications include multiband circular polarization transformers and wave plates,chirality based sensors etc.Theoretical studies on metamaterials for their enormously strong chiral responses,covers various structural designs such as helical,split ring,combined U-or L-shape,twisted arc,twisted rosette,metallic cut wire structures etc.However,the research on the actual devices is limited because the actual structures are normally generated on a substrate,which interferes with the optical behavior of the metamaterial itself,making it difficult to distinguish the contributions between the two factors.In order to study the optical behavior of the metamaterial,developing a method to create free-standing metamaterial structures is crucial.Here we report a method for free-standing chiral metamaterials on SiNx membrane.First,a suspended SiNx membrane of 100 nm thickness is fabricated on a double-side-polished silicon substrate.The SiNx layer is deposited by LPCVD onto one side of the silicon substrate.On the other side multiple windows in the size of 1 mm by 1 mm are etched through the silicon substrate using KOH chemical with the protection of photoresist,leaving the SiNx film suspended.Then a JEOL 6300FS EBL system is used to create chiral patterns in the PMMA resist on the SiNx membrane.Afterwards,Reactive Ion Etching by Samco RIE system is applied with CHF3 and O2 to etch through the SiNx membrane to form the stencil mask.After depositing the metal film on top of the etched SiNx membrane,the free-standing metamaterial structures are created.With this method,free-standing chiral metamaterial structures are generated for optical behavior study within the visible frequency range.This facilitates enhanced experimental research on metamaterial devices in the study of artificial light manipulation.