Thermally stable bubble garnets (YCaRE)3(FeGe)5O12 (RE: rare‐earth ion) were studied as materials for high density and high speed bubble devices. Rare‐earth ions used were EuYb, EuTm, EuEr, Sm, SmLu and SmTm. These garnets were particularly useful for bubble materials with bubble diameters of 6 μm to less than 1 μm. For example, the temperature stabilities of submicron bubble garnet YCaSmLuGeIG were very good up to 140°C, temperature coefficients of the stripe width and bubble collapse field being −0.01%/°C and −0.2%/°C, respectively. Typical values of 4πMs, uniaxial anisotropy field and wall mobility of this garnet were 518 Gauss, 1650 Oe and 600 cm/sec⋅Oe, respectively. For the highly reproducible growth the feedback control technique of the growth process was applied for YCaEuYbGeIG with 3 μm bubble diameters which was used for 105 bits/chip bubble devices. By this technique the epitaxial growth of the garnet was well controlled resulting in an extremely high yield of films: for example, more than 60% for bubble collapse field Ho=140±3 Oe.