Chemical epitaxial growth of nanometer YIG films is proposed. Average surface roughness is ∼0.8 nm for 50 nm YIG films. The extracted Gilbert damping constant is as low as 1.4 × 10−3. YIG films are fabricated upon heavy metal Pt buffered GGG for the first time. Inhomogeneous linewidth for YIG/Pt/GGG has been greatly enhanced up to 108 Oe.