Abstract: An efficient method for fabricating dual well type structures uses the same number of masks used in single well type structure fabrication. In a preferred embodiment, the current invention allows low voltage and high voltage n-channel transistors and low voltage and high voltage p-channel transistors to be formed in a single substrate. One mask is used for forming a diffusion well, a second mask for both forming a retrograde well and doping the well to achieve an intermediate threshold voltage in that well, and a third mask for both differentiating the gate oxides for the low voltage devices and doping the threshold voltages to achieve the final threshold voltages.

Abstract: In one aspect, the invention includes a method of forming a gated semiconductor assembly, comprising: a) forming a silicon nitride layer over and against a floating gate; and b) forming a control gate over the silicon nitride layer. In another aspect, the invention includes a method of forming a gated semiconductor assembly, comprising: a) forming a floating gate layer over a substrate; b) forming a silicon nitride layer over the floating gate layer, the silicon nitride layer comprising a first portion and a second portion elevationally displaced from the first portion, the first portion having a greater stoichiometric amount of silicon than the second portion; and c) forming a control gate over the silicon nitride layer.

Abstract: An efficient method for fabricating dual well type structures uses the same number of masks used in single well type structure fabrication. In a preferred embodiment, the current invention allows low voltage and high voltage n-channel transistors and low voltage and high voltage p-channel transistors to be formed in a single substrate. One mask is used for forming a diffusion well, a second mask for both forming a retrograde well and doping the well to achieve an intermediate threshold voltage in that well, and a third mask for both differentiating the gate oxides for the low voltage devices and doping the threshold voltages to achieve the final threshold voltages.

Abstract: The use of separate masks to pattern the same layer of material formed over a semiconductor substrate serves to reduce or avoid lithographic rounding effects. A layer of material formed over a semiconductor substrate may be patterned in accordance with separate masks. A first mask may have a feature which is substantially perpendicular to a feature of a separate second mask. Where the layer is patterned to form transistor gates, the minimum amount each transistor gate should extend over the edge of its active region under the endcap rule may be reduced. In this regard, a line pattern mask and a gap mask are used to avoid lithographic rounding effects in forming the transistor gates. Semiconductor devices may thus be fabricated with higher packing densities as transistors may be placed closer to one another.