Abstract: Method of manufacturing a semiconductor device comprising MOS-transistors of a first type (A) having a gate oxide (3) of a first thickness and MOS-transistors of a second type (B) having a gate oxide (10) of a second, greater thickness. In this method, active regions (4) and field oxide regions (5) are formed in a silicon body (1). Then a layer of gate oxide (6) of said first thickness is formed on the active regions, on which a layer (7,8) of an electrode material is deposited. In the layer of electrode material, the gate electrodes (9) for the transistors of the second type are formed. Then an oxidation treatment is carried out, in which the thickness of the gate oxide under said gate-electrodes increases to the desired second thickness (10). During these processes, the electrode layer on the active regions of the MOS-transistors of the first type is not disturbed. The gate electrodes for the transistors of the first type are formed after the oxidation treatment.

Abstract: Method of manufacturing a semiconductor device comprising MOS-transistors of a first type (A) having a gate oxide (3) of a first thickness and MOS-transistors of a second type (B) having a gate oxide (10) of a second, greater thickness. In this method, active regions (4) and field oxide regions (5) are formed in a silicon body (1). Then a layer of gate oxide (6) of said first thickness is formed on the active regions, on which a layer (7,8) of an electrode material is deposited. In the layer of electrode material, the gate electrodes (9) for the transistors of the second type are formed. Then an oxidation treatment is carried out, in which the thickness of the gate oxide under said gate-electrodes increases to the desired second thickness (10). During these processes, the electrode layer on the active regions of the MOS-transistors of the first type is not disturbed. The gate electrodes for the transistors of the first type are formed after the oxidation treatment.

Abstract: The present invention provides a method of forming a semiconductor structure (10) comprising a substrate (12) having a patterned Oxide-Nitride-Oxide (ONO) insulating layer (22) provided over a portion of the substrate (12). The invention employs an Oxide-Nitride-Silicon structure (38, 40, 42) as the basis for the ONO layer, which has the advantage that the upper silicon sub-layer (42) of the structure is resistant to damage during the photoresist stripping step of a patterning process and is then available for re-oxidizing into an oxide layer forming the upper sub-layer of the required ONO structure.