The need for higher manufacturing yields and improved operational reliability of semiconductor devices and circuits has led to a continuing scrutiny of all processing steps. Topic of the present paper is the effect of addition of chlorine or one of its compounds during silicon oxidation. After discussing oxidation kinetics in the presence of halogens and the metallurgical aspects of the process, a comprehensive review of the electrical effects is given. Attention is paid to the elimination of oxide charge centers and interface states, surface stabilization and enhanced dielectric behavior in MOS structures, and to the increased minority carrier lifetime in the silicon substrate. The improvements in device characteristics which have been attained using this method are summarized.