**Abstract**

Plasmonic nanostructures have attracted growing interest over the last decades due to their efficiency in improving the performance in various application fields such as catalysis, photovoltaics, (opto-)electronic devices, and biomedicine. The behavior of a specific metal plasmonic system depends on many factors such as the material, the size, the shape, and the dielectric environment. The geometry, that is, size and shape of both single plasmonic elements and patterned arrays of plasmonic nanostructures, plays an essential role, and it provides considerable freedom to tune the plasmonic properties of a single plasmonic nanostructure or any combination of nanostructures. This freedom is mainly used in the application fields of surfaceenhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS). In this context, the chapter encompasses how the geometry of the SERSactive plasmonic nanostructures and tips with/without metal substrates used in TERS influences the localized surface plasmon resonances of the plasmonic systems.

**Keywords:** plasmonics, metal nanostructures, geometry, SERS, TERS, simulation
