The development of an efficient photocatalyst capable of producing enough hydrogen for applications in everyday life under direct sunlight exposure is still challenging. In this work, a new concept for a three-dimensional microstructured photocatalyst is proposed, in which a standard deep-reactive ion etching process allows for the optimization, fabrication and subsequent deposition of TiO2 thin films by physical vapor deposition for H2 production by direct water splitting. After the development of enlarged surface microstructures, the composition and morphology of the 3D TiO2 photocatalyst were characterized by XRD, XPS, UV/Vis spectroscopy and SEM. Furthermore, the influence of the area enlargement factor on the 3D photocatalyst surface morphology and its photocatalytic performance under UV–visible irradiation was thoroughly analyzed and corroborated by electrochemical experiments. The photocatalyst exhibited an increase in H2 production by almost a factor of 12 compared to conventional planar TiO2 films. The H2 production was further improved by a factor of 4 through the introduction of Au nanoparticles grown on top of the TiO2 layer. The advantages and development of robust and hierarchical photocatalysts using microelectromechanical fabrication techniques are highlighted as potential solutions for a broad range of applications from photocatalysis, electronics, and sensing elements to 3D metamaterials.