A high‐speed chemically amplified positive resist based on poly(p‐hydroxystyrene) has been developed for x‐ray lithography. This resist, CANI (meaning chemically amplified resist) by Nippon Telegraph and Telephone Corporation, has a sensitivity of 50–70 mJ/cm2to soft x rays while maintaining sub‐0.25‐μm resolution and a rather large dose margin of 34%–40%. Another advantage of CANI is that the theoretical weight loss from the removal oft‐butyl protecting groups by chemical amplification reactions is less than 4 wt %. This leads to little volume shrinkage at uv cure and reactive ion etching processes, and thus promises good controllability of pattern feature sizes between lithography and subsequent plasma etching processes.