The borophosphosilicate glass(BPSG) layers as the filling coatings to silica-based planar lightwave circuits were obtained by using plasma enhanced chemical vapor deposition with SiH_4/N_2O and PH_3,B_2H_6.The influence of dopants on refractive index of BPSG layers was discussed and the methods related the refractive index of BPSG layers to PH_3 and B_2H_6 gases flows were suggested.The annealing effects of BPSG layers were studied on its optical features and surface map at different annealing conditions.By using multiple deposition followed by annealing,the perfect BPSG layers,which are without void and gap and with fine smoothness,were fabricated.