We found that B diffusion profiles in polysilicon can be regarded as having a constant surface concentration, N-0. Using this finding, we derived a B diffusion profile model and identified the diffusion coefficient of B in polysilicon. We also derived the model for the critical time, t(1), to flatten the B profile in a polysilicon gate. Using the critical time for B penetration through the gate oxide, t(2), we determined the allowable diffusion time t as t(1) < t < t(2). We showed that B implantation provides a thermal budget wide enough to fabricate p(+) polysilicon gates for 0.1 mu m complementary metaloxide semiconductor with pure SiO2.