Chemical vapor deposited (CVD) nanocrystalline diamond films and novel lithography techniques were used to fabricate short wavelength photonic slab crystals (PhC) with feature sizes below 100 nm. CVD diamond was chosen as a promising material for photonic structures due to a large bandgap (5.45 eV) and high index of refraction (2.38). Two methods of fabricating diamond PhC, both based on electron-beam lithography, have been developed. For structures with a high filling coefficient, the best results were obtained with an organic-inorganic bilayer negative resist structure utilizing a polymer-based resist as the bottom layer and a flowable oxide (FOx-12) as the top layer. After E-beam exposure and developing, the FOx pattern was used as a mask for dry etching the bottom resist layer. The resulting structure provides rigid overhang with very fine feature size control that is not affected by the surface roughness of the diamond film. A metal mask was deposited over the patterned bilayer resist followed by lift-off. The remaining metal pattern was used as a protective mask for a highly anisotropic oxygen plasma etch of the nanodiamond film. With the proper choice of the metal mask, this method can be applied to a wide range of materials and feature sizes. Relatively thin nanodiamond structures with a low filling coefficient can be fabricated in a simpler process that utilizes E-beam patterned FOx-12 as an etch mask. Freely suspended PhC slabs were formed by wet etch removal of the sacrificial oxide layer underneath the diamond film. We will present fabrication techniques, experimental data of the mechanical properties of the nanodiamond resonator, and analysis of the optical bandgap of the nanodiamond PhC.