The incorporation of nitrogen and oxygen in polysilicon has been examined by SIMS. The analysis, combined with C-V measurements and ion implantation, has been used to correlate the incorporation of the two species with the fixedcharge density at the back polysilicon/Si02 interface. Laser recrystallization with a silicon-nitride encapsulation layer results in the inclusion of 2–4 × 1017 cm−3 nitrogen atoms in the polysilicon; if an oxide capping layer is used, the nitrogen level observed is at the background of the SIMS system (~1015cm−3). Either type of capping layer results in 3−4×1018cm−3 oxygen atoms being incorporated into the polysilicon. Implantation of nitrogen into the polysilicon before recrystallization increases the fixed-charge density Nf,b) at the back interface, while implanted oxygen decreases Nf, b. The high Nf, b found with a nitride capping layer is attributed to deposition of nitrogen or SiNx at the back interface.