JPS553650A - Semiconductor device production - Google Patents

Abstract

PURPOSE:To enhance withstand voltage between the second gate electrode and the substrate in a semiconductor device, a thick, low-temperature oxidized layer is formed near the boundary of the first and second gate oxide film, thereby preventing the formation of extremely thin layer at the second gate oxide layer boundary. CONSTITUTION:A semiconductor substrate 11 is deposited with an oxide layer 17 and a first electrode material layer 18, and a selected portion of which is deposited with a mask 19' of Si oxide or Si nitride layer. Side etching is applied to the layer 18 so as to leave an extended edge 20 of layer 19', forming a first gate electrode 18'. The gate electrode 18' is used as mask to etch the layer 17, to form a first gate oxide layer 17'. Vapor phase growing process is used to coat a low temperature oxide layer 21 to fill sufficiently a space 22 enclosed by the extrusion 20 and the substrate 11. Entire surface etching is applied to the layer 21 to leave only the layer 22' between the substrate 11 and the extruded edge 20. An oxide layer 23 and second electrode material are coated and, by selective etching, a second gate electrode 24 and a second gate oxide layer 23' are sequently formed.