No, carbon can be created through various processes in addition to supernovae. While supernovae are one of the primary sources of carbon in the universe, they are not the only means by which carbon is formed.
In stars like our Sun, carbon is synthesized through a process known as the triple-alpha process. In this process, three helium nuclei (alpha particles) combine to form a carbon-12 nucleus. This occurs in the stellar core when the temperature and pressure are high enough to overcome the electrostatic repulsion between the positively charged alpha particles.
Furthermore, carbon can also be formed in the later stages of stellar evolution, during the helium and carbon burning phases in massive stars. These processes involve nuclear fusion reactions that convert helium into carbon and other heavier elements.
It is important to note that while supernovae can produce and distribute large amounts of carbon and other elements into the surrounding space, there are other sources of carbon as well. Processes like stellar winds, stellar outflows, and planetary nebulae can also contribute to the enrichment of carbon in the interstellar medium.