Proximity X-ray Lithography (PXL) has been demonstrated to be powerful tool for fabricating patterns at the 130-nm technology node and to be extendable to the 70-nm node and below. On the other hand, the capabilities of optical lithography have now reached the 150-nm node, and it is widely discussed that it will be applicable to the 100- and 70-nm nodes. In this study, we have investigated the printing characteristics of PXL and compare them to those of ArF and F2 optical lithography for several model patterns of DRAMs, SRAMs, and logic devices at the 100- and 70-nm nodes. We used aerial image simulations and carried out PXL exposure experiments to confirm the simulation results. Both the aerial images and the exposure results show that PXL has sufficient resolution for patterns with a 100-nm design rule and offers a wide latitude in the proximity gap. For ArF and F2 lithography with a Levenson-type mask, the same patterns were resolved with a lower fidelity and the depth of focus (DOF) was less than 0.2 micrometer. No resolution enhancement techniques (RET), such as optical proximity correction (OPC) to masks, are required in PXL; but they are indispensable in optical lithography. At the 70-nm node, PXL provides acceptable resolution, even at a gap of 10 micrometer; and the simulations show that the resolution can be increased by setting the gap in the range of 5 - 10 micrometer.