a method of measuring a width of an undoped or lightly doped polysilicon line is disclosed . the width measuring method includes generating carriers in the polysilicon line with an energy source ; measuring a capacitance between the polysilicon line and a substrate separated from the polysilicon line by a dielectric layer ; and determining a line width of said polysilicon line from the measured capacitance . the capacitance measurement includes connecting first and second probes to the polysilicon line ; connecting a third probe to the substrate ; connecting a first terminal of a capacitance meter to the first and second probes ; connecting a second terminal of the capacitance meter to the third probe ; and applying a direct current bias across the first and second probes . a capacitor may be connected between the first and second probes . further steps include , connecting a fourth probe to a conductor that supports the substrate ; and connecting the fourth probe to the third probe .