EFPGAs give designers the flexibility to make changes at any point in the chip's life span, even in the customers' systems. Though, eFPGA are not efficient from an integration perspective, making proper dimensionning and tailoring mandatory. Unfortunately, designing an eFPGA is a complex and error-prone task. Even though automatic generation from high level models can produce correct-by-construction layouts, integration remains complex due to process variation. A key point is then to reduce the technology dependency.This paper presents the ELNATH project in which three implementations of the same architecture have been addressed: overlay, eFPGA, and 55 nm FPGA thanks to an open-source integrated tool flow that supports defining, implementing and programming reconfigurable architectures.