The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 11, 1998
Filed:
May. 05, 1997
Yugo Tomioka, Tokyo, JP;
Yasuo Sato, Tokyo, JP;
Nippon Steel Corporation, Tokyo, JP;
Abstract
A nonvolatile semiconductor storage device in which a composite gate of a floating gate memory cell transistor and a gate electrode of a peripheral MOS transistor are formed in the same lithography process and a manufacturing method thereof. A polycrystalline silicon film and an ONO film are formed on a well region through a gate oxide film and a tunnel oxide film. A polycrystalline silicon film is formed after removing the ONO film in the right region. A floating gate and a control gate of the memory cell transistor and a gate electrode of the select transistor are formed with photoresist as a mask. Thereafter, ions of impurities are implanted and diffused in a transverse direction, thereby to form an impurity diffused layer. With this, since the impurity diffused layer is formed by transverse diffusion of impurities after the tunnel oxide film is formed, it is possible to prevent deterioration of the film quality of the tunnel oxide film.