Since the Bible says that God “created all things,” some have concluded that God must have created the Devil. (Ephesians 3:9; Revelation 4:11) The Bible clearly shows that he did not. Jehovah created the person who became the Devil.
Talking about God the Bible says “Perfect is his activity, for all his ways are justice. A God of faithfulness, with whom there is no injustice; righteous and upright is he.” (Deuteronomy 32:3-5) This scripture shows that God only creates perfect things, so to say that God could create the sinful Satan is false according to the Bible.
From that statement at Deut 32:3-5, we can conclude that Satan had at one time been perfect and righteous, namely, one of God’s angelic sons, an Angel. At John 8:44, Jesus said that the Devil “did not stand fast in the truth,” implying that Satan had at one time been truthful and guiltless.
We can also see Satan at times walked among and with the Angels before God.
(Job 1:6) “…Now it came to be the day when the sons of the [true] God [the Angels] entered to take their station before Jehovah, and even Satan proceeded to enter right among them…”
So Satan at one time was an Angel that forsook his position and thus came to be known as the Devil. This has also happened to other Angels too.
(Jude 6) "...And the angels that did not keep their original position but forsook their own proper dwelling place he has reserved with eternal bonds under dense darkness for the judgment of the great day..." These Angels came to be known as Demons, with Satan the ruler of the Demons
(Matthew 9:34) "...But the Pharisees began to say: “It is by the ruler of the demons that he expels the demons...”
We can see also that Satan has in his control Angels, of course these angels under his control are known to use by the title Demons, however they can still be rightly called Angels.
(Revelation 12:9) "...So down the great dragon was hurled, the original serpent, the one called Devil and Satan, who is misleading the entire inhabited earth; he was hurled down to the earth, and his angels were hurled down with him..."
Hope I've helped.