A method of programming a nonvolatile memory cell is provided according to an embodiment of the invention. The nonvolatile memory cell includes a substrate; and a select transistor, a following gate transistor, and an anti-fuse transistor comprising a first gate oxide layer, disposed on the substrate and coupled in series with each other. The programming method includes applying to said nonvolatile memory cell a variable DC voltage source comprising at least one high voltage part for forming a trapping path within the first gate oxide layer and at least one low voltage part for crystallizing the trapping path into a silicon filament.