An ion beam milling technique is used to planarize the SiO2steps in 8 μm period field‐access magnetic bubble devices. A photoresist coating is first applied over the SiO2steps to produce a smooth surface. The resist layer is then ion milled using conditions that give equal milling rates for the resist and SiO2films. The planar resist surface is thus preserved in SiO2after the resist layer is completely milled away. Magnetic bubble devices fabricated by this process are shown to operate at much lower in‐plane drive field than similar devices fabricated by conventional nonplanar processes.