Several sets of x‐ray masks for a metal–oxide semiconductor (MOS) device program were fabricated using boron‐doped silicon as the membrane and gold as the absorber. The metrology of the mask sets was characterized. Mask‐to‐mask overlay error is ≪0.12 μm (3σ) including measurement error. Absorber induced distortion is not the dominating mask error. (Lack of better measurement systems and techniques preclude exact analysis of errors.) Quarter‐micron patterns have been resolved using a multilayer resist system. Linewidth variations are ≪0.017 μm (1σ) across the entire membrane. The mask sets have been successfully used to fabricate fully scaled n‐type MOS circuits.