CHF@sub 3@ plasmas are widely used for dry etching of SiO@sub 2@. There are many reports on the diagnostics of CF@sub x@ radicals in CHF@sub 3@ plasmas. However, reliable diagnostics of H atoms in CHF@sub 3@ plasmas have not ever been carried out. H atoms play an important role in scavenging F atoms which obstruct selective etching of SiO@sub 2@. In addition, excess H atoms may results in the damage of Si. Accordingly, the reliable diagnostics of H atoms in CHF@sub 3@ plasmas is an important issue. In the present work, we measured the absolute H atom density in high-density CHF@sub 3@ plasmas by (2+1)-photon laser-induced fluorescence spectroscopy.@footnote 1@ In addition, the absolute densities of CF and CF@sub 2@ radicals were also measured by laser-induced fluorescence. The experiments were carried out in a linear machine with a uniform magnetic field of 1 kG. Helicon-wave discharges were obtained by applying various rf powers to a helical antenna wound around a glass tube of 3 cm diameter. Since the plasma was confined radially by the external magnetic field, we had a slender plasma column with a diameter of 3 cm at the center of the cylindrical vacuum chamber. The H atom density was mainly on the order of 10@super 13@ cm@super -3@ at a CHF@sub 3@ gas pressure of 5 mTorr. The H atom density increased with the electron density of the plasma. Contrary to the H atom density, the CF@sub 2@ radical density was a decreasing function of the electron density. The H atom density was higher than the CF@sub 2@ radical density in plasmas with electron densities higher than 10@super 12@ cm@super -3@. The spatial distribution of the H atom density in low-density plasmas was roughly uniform, while in high-density plasmas, slightly hollow distributions (i.e., the H atom density in the plasma column was lower than that in the outside region) were observed in the H atom density. @FootnoteText@ @footnote 1@K. Sasaki, M. Nakamoto, and K. Kadota, Rev. Sci. Instrum., in press.