From Dr. Anatolios’s book Retrieving Nicea: The Development and Meaning of Trinitarian Doctrine, describing the theology of Eusebius of Caesarea (c. 260 – c. 339):
Eusebius conceives of the Spirit as the next level down in the chain of being and willing that descends from the Father and the Son. While he is ambiguous on the neuralgic question of the creaturehood of the Son, he is clear that the Spirit is a creature, the first to come into existence through the agency of the Son. The Spirit is a self-subsistent being who indwells those who are sanctified and bestows on them the gifts of holiness. In one passage, Eusebius says that the Spirit is neither God nor Son. However, such a statement is more difficult to interpret than at first appears. This is so not only because the notion of divinity is still fairly elastic at this point, such that many could speak of the Son as divine but not “true God,” but also because Eusebius in particular is preoccupied with scriptural titles… [and] the Spirit is not scripturally identified as either God or Son. If “all things came to be through the Son,” then the Spirit is the first of the creatures who came into existence through the Son; the Spirit sanctifies the faithful and is one of the “holy Trinity.” (p. 67, emphases added)
I.e., the holy trinity, yes, not the triune God, but the triad of the one God and these two lesser deities.
I think that Tertullian and Origen and Justin also held the Spirit to be the third greatest deity. You see a similar view in the famous English unitarian John Biddle (1615-62).