Chemically sensitive sensor with lightly doped drains

A method of making a chemically sensitive sensor, comprising:

• forming a substrate with a first conductivity type of dopant;
• building an epitaxial layer using the same conductivity type dopant used to form the substrate, but made less dense than the dopant on the substrate;
• forming an electrode layer on the epitaxial layer formed from a different, second conductivity type of dopant than the first conductivity type of dopant used to form the substrate, wherein the density of dopant on both the electrode layer and the substrate are similar;
• masking and etching the electrode layer to produce gates and electrodes;
• creating a first lightly doped region adjacent to one of the electrodes using a multidirectional implant technique, wherein the first lightly doped region is formed from a dopant of a conductivity type opposite the epitaxial layer dopant;
• producing diffusion nodes that are self-aligned with the electrodes next to the gates, a first of said diffusion nodes contiguous with the first lightly doped region, from a dopant of a conductivity type similar to the gates, electrodes, and lightly doped region;
• and
• forming a floating gate electrode, electrodes above the diffusion area, and contacts for electrodes by alternating layers of insulation, dielectric, conductive and metal layers.