GdxSc2−xO3 and AlxSc2−xO3 have been investigated as potential high-k intergate dielectric (IGD) in planar NAND flash technology, such as hybrid floating gate (HFG). We have examined the atomic layer deposition (ALD) of Sc2O3, GdxSc2−xO3, and AlxSc2−xO3 on Si using Sc(MeCp)3, Gd(iPrCp)3, TMA, and H2O as precursors. The composition of GdxSc2−xO3 and AlxSc2−xO3 ranged from 4% to 76% Gd and from 7% to 66% Al, respectively. All compositions show linear growth behavior. While pure Sc2O3 is crystalline as-deposited, the layer becomes amorphous once ∼20% of Al is added. The (222) reflection of the cubic phase is also seen for GdxSc2−xO3 with less than 9% Gd. The bandgap of as-deposited GdxSc2−xO3 decreases with increasing Gd content while the opposite trend is observed for AlxSc2−xO3. A k-value of ∼21 can be obtained for GdxSc2−xO3 with approximately 26–52% Gd, irrespective of the Gd content. For AlxSc2−xO3 on the other hand, a maximum k-value of ∼19 is achieved with ∼48% Al. Although the k-value of AlxSc2−xO3 is lower than that of GdxSc2−xO3, its large breakdown field makes this material more suitable for HFG flash applications.