Patent ID: 6713331
Filing Date: 2004-03-30
Classification: H01L

Abstract:
A method of manufacturing a semiconductor device comprising the steps of:forming a first photo resist film having a first opening in a source forming region on a first conductive type semiconductor substrate and also having a second opening, a size of which is larger than that of the first opening, in a drain forming region; forming second conductive type sourceâ€¢drain regions of low concentration when a first impurity of the second conductive type is subjected to ion implantation into the substrate by using the first photo resist film as a mask and then the second type first impurity is diffused; forming an element separation film in a predetermined region by selectively oxidizing while an oxidation-resistant film formed on the substrate is being used as a mask and also forming a first gate oxidation film, further forming a second gate oxidation film in regions except for the element separation film and the first gate oxidation film after the element separation film and the first gate oxidation film having been formed; forming a gate electrode in such a manner that the gate electrode lies across the first and the second gate oxidation film; forming a second photo resist film having a third opening in the source region of low concentration and also having fourth opening in a region separate from the other end portion of the gate electrode in the drain region of low concentration; and forming second conductive type sourceâ€¢drain regions of high concentration when ions of a second impurity of the second conductive type are implanted into the substrate by using the second photo resist film, gate electrode, element separation film and first gate oxidation film as a mask.