Contrary to what many Christians believe, God didn't create Satan. I will go out on a limb here and argue that it is blasphemous to say that God created Satan, because God would never create a being who he knew would wreck so much havoc on humanity.
Like all other condemned spirits, Satan was born a human, lived his life then died, and went to hell. And he became the Devil. Satan, who told me his real name is Raj, was a brahmin (priest) caste Hindu 4,500 years ago who dedicated his life to serving man-made gods like Krishna and Shiva (so he told me). For this reason, Satan did not inherit salvation. Last fortnight, Satan invaded my dream and tried to cajole me into a bargain again, which I promptly rejected. I asked him how he became the Devil, but he didn't tell me, so I don't know how he became the leader of hell.