In one aspect, a method of forming a CMOS device includes forming nanowires suspended over a BOX, wherein a first/second one or more of the nanowires are suspended at a first/second suspension height over the BOX, and wherein the first suspension height is greater than the second suspension height; depositing a conformal gate dielectric on the BOX and around the nanowires wherein the conformal gate dielectric deposited on the BOX is i) in a non-contact position with the conformal gate dielectric deposited around the first one or more of the nanowires, and ii) is in direct physical contact with the conformal gate dielectric deposited around the second one or more of the nanowires such that the BOX serves as an oxygen source during growth of a conformal oxide layer at the interface between the conformal gate dielectric and the second one or more of the nanowires.