A one time programmable memory cell having twin wells to improve dielectric breakdown while minimizing current leakage. The memory cell is manufactured using a standard CMOS process used for core and I/O (input/output) circuitry. A two transistor memory cell having an access transistor and an anti-fuse device, or a single transistor memory cell 100 having a dual thickness gate oxide 114 & 116, are formed in twin wells 102 & 104. The twin wells are opposite in type to each other, where one can be an N-type well 102 while the other can be a P-type well 104. The anti-fuse device is formed with a thin gate oxide and in a well similar to that used for the core circuitry. The access transistor is formed with a thick gate oxide and in a well similar to that used for I/O circuitry.