JPS5583263A - Mos semiconductor device - Google Patents

Abstract

PURPOSE:To accelerate the operating speed of a transistor by burying an oxide layer in each of the bottoms of source and drain regions when diffusing the source and drain regions at both sides of a channel region. CONSTITUTION:A gate insulating film 10 buried internally with a gate electrode 10' is formed on a semiconductor substrate provided with a thick field oxide film 5 on the periphery thereof. Then, with the film 10 as a mask oxygen ion is implanted into the substrates at both sides of the mask while controlling the acceleration voltage to thereby produce maximum oxygen density region at predetermined depth, the substrate is then annealed to thereby form oxide layers 17 and 18. Then, shallow source and drain regions 13 and 14 are formed thereon by ion implantation or diffusion, and electrodes 13' and 14' are mounted thereat. Thus, the extension of a depletion layer from the channel layer 16 to the channel region 16 can be reduce to the degree to be ignored to thus become a short channel, and the dielectric constant of the oxide layer is lower than the substrate to thereby improve the operating speed of the transistor.