JOEL - Demigod is not a scriptural term but is a mythological term for someone who begins his life as half mortal and half God having one mortal parent and one god parent(eg. Hercules or Achilles).
The difference for Jesus is that He was already a full-fledged God before He was born to Mary, even though he did not yet have a body. He condescended to a mortal life when he was born of a mortal woman and God the Father. He came in condescension, leaving his station as the Lord Omnipotent to undertake His mission of pain and humiliation.
The Book of Mormon prophet Nephi (c. 600 B.C.) was asked by an angel, "Knowest thou the condescension of God?" (1 Ne. 11:16). Nephi was then shown in a vision a virgin who was to become "the mother of the Son of God, after the manner of the flesh" (verse 18), and the temptations and pain He would suffer in His mortal state. This concept of condescension is not included in the deffinition of a demigod.