Manufacture of semiconductor device

Abstract

Abstract PURPOSE:To thin the thickness only of a high resistance section in the same polysilicon layer while forming a low resistance section at a proper position by implanting ions only to sections except the high resistance section by shaping a silicon oxide layer to a section, in which a silicon nitride film is not formed, in the surface of the polysilicon layer, removing the silicon nitride film and implanting ions to the polysilicon layer again to shape the low resistance section. CONSTITUTION:An Si3N4 film 15 is shaped onto second layer polysilicon 14 by using a low-pressure CVD method. The film 15 is patterned so that the film 15 is left only on sections as low resistance sections 14a, 14b in the second layer polysilicon 14 through photolithography. Only the high resistance section 14a is oxidized selectively, and an oxide film 14d is formed. The film 15 is removed through dry etching by a fluorine gas. Ions are implanted to the whole surface of the element. An impurity is diffused in specified concentration to low resistance sections 14b, 14c exposed through the ion implantation, and resistance is lowered up to a desired resistance value.

Inventors

• 👤 Noriaki Okada

Bibliographic Details