High aspect ratio deep reactive ion etching (DRIE) of single-crystalline silicon carbide (SiC) holds promise for fabricating next-generation harsh-environment (e.g. high temperature, high power, reactive environments) micro- and nanoelectromechanical systems (MEMS/NEMS). However, unlike Si, SiC microfabrication via DRIE remains in its infancy. In particular, high aspect ratio SiC DRIE poses a significant challenge in SiC MEMS development. To tackle this issue, SiC DRIE process parameters (e.g. cycle time, power, backside substrate cooling) were investigated to achieve high aspect ratio SiC microstructures with close to vertical sidewalls. Overall, the SiC processing work described here helps to bridge the knowledge gap between Si and SiC microfabrication and support the adaption of single-crystalline SiC-based micro- and nanodevices.