Semiconductor Device Well Isolation for High- and Low-Voltage Integration

The device is divided into two distinct well regions: a first well region for high-voltage elements and a second well region for low-voltage elements. This segmentation physically separates the high-voltage and low-voltage circuits, preventing electrical interference while maintaining high integration by keeping both regions on the same substrate.

Different regions of the device are given different electrical characteristics through selective doping. The first well region is optimized for high-voltage operation with appropriate doping concentrations, while the second well region is optimized for low-voltage operation. This local differentiation allows each region to operate at its optimal voltage level without interfering with the other.

The solution moves from a two-dimensional layout optimization to a three-dimensional structure by forming gate electrode layers stacked in the vertical direction. Multiple gate electrodes can be positioned at different heights, allowing the device to achieve high-voltage operation through vertical stacking rather than horizontal expansion, thus reducing the planar area occupied by each element.

The gate electrode structure employs nested or stacked configurations where multiple gate electrodes are positioned one above another in the vertical direction. This nesting approach allows the device to pack more functional elements into a smaller planar area while maintaining the thick gate insulating layers necessary for high-voltage operation.

The gate insulating layers and gate electrode layers are formed in a predetermined stacked sequence during the fabrication process. By establishing the vertical stacking structure early in the manufacturing process, subsequent alignment steps can be optimized to match this pre-established framework, reducing the overall manufacturing precision requirements compared to forming all layers simultaneously.

The fabrication process is divided into separate stages for forming different gate electrode layers. Each gate electrode layer can be formed and aligned independently using the underlying structure as a reference, breaking down the complex multi-layer alignment task into manageable sequential steps that reduce cumulative alignment errors.