JPS5568672A - Fabrication of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the ON voltage and trigger current of a thyristor while shortening the step of fabricating a semiconductor device by similarly diffusing opposite conductivity layers on both front and back surfaces of a one-conductivity semiconductor substrate and etching to remove one layer until the surface becomes predetermined impurity density. CONSTITUTION:SiO2 films 10, 11 are coated on both front and back surfaces of an n-type silicon substrate 1, openings 12, 13 are perforated on both ends thereof, and p-type impurity is diffused thereat to thereby form a p-type isolation region 4 in the substrate 1. Then, an opening 14 is perforated at the surface film 10, the back film 11 is removed, the p-type impurity is diffused thereat, a p-type gate region 2 is formed in the substrate 1 exposed with the opening 14, and a p-type anode region 3 is simultaneously formed on the back surface of the substrate 1 to thereby connect the region 3 to the region 4. Then, the film 10 is removed, the surface of the exposed substrate 1 is polished, the region 2 is formed thinner than the region 3 by t1-t2 so as to set the surface impurity density to predetermined value. Then, the entire surface is coated by a SiO2 film 9, an opening 15 is perforated, and an n-type cathode region 5 is diffused in the region 2.