God did not create Satan. The Hebrew translation of "ha satan" is "accuser" or "one who opposes." So, Satan is not technically a proper name, although that is often how people refer to the Devil.

Devil comes from the Greek word "diaballein," which means "to throw across." A more appropriate translation would be to throw apart. The Devil seeks to tear people apart, often by manipulating their emotions.

God did not create opposition. God did, however, give his creatures freedom. That freedom includes the possibility of serving God or denying God.

God created Lucifer, who was the highest of all the angels. The name means "bearer of light." As an angel, Lucifer also had freewill. Rather than freely choosing to serve God, Lucifer denied God and was therefore cast out of heaven. It was then that Lucifer became "ha satan" or "one who opposes" God, also known as the Devil.