We describe all-ultra-high-vacuum selective area growth based on surface nitridation and scanning tunneling micros-copy (STM) lithography. We pattern an amorphous nitrified GaAs surfaces by STM lithography, and can grow an array of uniform 6.4±0.8 nm-high GaAs dots successfully on the areas (50 nm×50 nm) from which the nitrided mask is re-moved by STM lithography. For uniformity in such nm-scale growth, the window area should be larger than the “nucleus-occupied area”, defined as the inverse of the saturated nucleus density, and the window separation should be larger than the diameter of the “nucleus-occupied area”.