We systematically examined thermal diffusion processes of boron into silicon including the predeposition and the drive-in diffusion using a liquid boron tribromide (BBr3) source, in order to enable its application to buried-gate-type static-induction thyristors (SIThys). A low sheet resistance of 22 +/- 1 Omega/square with a good in-wafer uniformity of within +/- 5% and with a good wafer-to-wafer uniformity of within +/- 1% was successfully achieved in the predeposition process using the liquid BBr3 source. The effect of the silicon boride (SiBx: 4 <= x <= 6) phase on the stability of the boron-diffused layers after drive-in diffusion was also investigated, and it was concluded that the removal of the silicon boride phase is important for obtaining stable drive-in diffused layers. The I-V characteristics of p-n junctions in SIThys fabricated using the liquid BBr3 source exhibited better properties than those fabricated using a solid boron nitride (BN) source. The results of the recombination-lifetime measurement indicated that high-quality p-n junctions were realized for boron-diffused wafers prepared using the liquid BBr3 source, in comparison with those prepared using the solid BN source. (c) 2005 The Electrochemical Society. All rights reserved.