Rambam's Moreh Nevuchim Book III, chap. 22 discussing sefer Iyove

"...the Talmud says as follows:  "Rebbe Shimeon ben Lakish, says: "The adversary (satan), evil inclination (yezer ha-ra'), and the angel of death, are one and the same being."   Here we find all that has been mentioned by us in such a dear manner that no intelligent person will be in doubt about it. It has thus been shown to you that one and the same thing is designated by these three different terms, and that actions ascribed to these three are in reality the actions of one and thesame agent. Again, the ancient doctors of the Talmud said: "The adversary (satan) goes about and misleads, then he goes up and accuses, obtains permission, and takes the soul." You have already beentold that when David at the time of the plague was shown the angel" with the sword drawn in his hand stretched out overJerusalem."

Rambam and Rebbe Shimeon ben Lakish teach that "satan" as discussed in Iyove and other instances,  refers to a person's own instincts. Not "part" of God, or another force in the universe.

Additionally, as all Chazal write, God cannot possess parts. This is a fundamental, the violation of which one forfeits their Olam Haba, as Rambam teaches. See his 13 Principles and Yesodei haTorah.