Leatherface is a fictional character created for the film. The character's appearance and actions are entirely the product of makeup, acting, and special effects.
While there have been some real-life cases of serial killers who wore masks or engaged in similar acts of violence, Leatherface is not based on any one specific person.
The use of real-life inspiration for fictional characters is common, but in this case, the creators of the Texas Chainsaw Massacre franchise opted to create a purely fictional character.