A capacitor for a single-poly floating gate device is fabricated on a semiconductor substrate along with low and high voltage transistors. Each transistor has a gate width greater than or equal to a minimum gate width of the associated process. A dielectric layer is formed over the substrate, and a patterned polysilicon structure is formed over the dielectric layer. The patterned polysilicon structure includes one or more narrow polysilicon lines, each having a width less than the minimum gate width. The LDD implants for low and high voltage transistors of the same conductivity type are allowed to enter the substrate, using the patterned polysilicon structure as a mask. A thermal drive-in cycle results in a continuous diffusion region that merges under the narrow polysilicon lines. Contacts formed adjacent to the narrow polysilicon lines and a metal-1 trace connected to the contacts may increase the resulting capacitance.