Hydrogen transport in low‐pressure chemical vapor deposited Si3N4has been investigated using samples consisting of a double layer of hydrogenated and deuterated nitride films. Concentration depth profiles of hydrogen and deuterium were measured using elastic recoil detection. Diffusion coefficients forDwere derived from the deuterium concentration depth profiles before and after annealing at temperatures in the range 700–1000 °C. The diffusion coefficient is characterized by an activation energy of 2.94 eV for the entire temperature range. Its value varies between 10−17cm2/s at 700 °C and 5×10−14cm2/s at 1000 °C.