[en] This doctoral thesis illustrates the studies of the variability and mismatch between ^N type MOSFET devices (nMOSFETs) with hexagonal (DnM), octagonal (OnM) and rectangular (CnM) gate geometry, considering four different types of bias of these nMOSFETs during the ionizing radiation procedure X-ray: I- without electrical bias or with all terminals (source, door, drain and substrate) open (Floating); II- with electrical bias of the devices in the operating state of “on-state” or “closed-switch” (On-state); III- with bias of the devices in the condition of analogue operation or operating as an amplifier (Analog); IV- with device bias in the state-off or “open-switch” operating condition (Off-state). Considering the Floating bias, during the X-ray ionizing radiation procedure, it appears that DnMs with an α angle of 90° reduce the mismatch between devices by 40.7% for the threshold voltage (VTH) and 56.8% for the subthreshold slope (SS), respectively, in comparison to the values found in the CnMs counterparts. Considering the On-state bias during the procedure of X-ray ionizing radiation, it is observed that OnMs with an α angle of ° and a 50% “c” factor improve the matching between devices by 57.4% for V_TH and 54.9% for SS compared to those found in CnM counterparts. In the Analog and Off-state bias during the X-ray ionizing radiation procedure, the DnMs and OnMs showed a better matching between devices compared to those obtained with the CnMs counterparts and with a 95% accuracy level. During the procedure of X-ray ionizing radiation in Floating mode, the maximum total ionizing dose (TID) used was in the order of up to 4.5 Mrad. In addition, during ionizing X-ray radiation procedures in On-State, Off-State and Analog modes, the maximum TIDs used were 200 krad for On-State and Analog modes and 20 krad for Off-State mode. Therefore, the Diamond and Octo layout styles can be considered as alternative layout strategies for the implementation of MOSFETs in order to enhance their tolerances to ionizing X-ray radiation, aiming at applications in integrated circuits (ICs) implemented with Complementary Metal-Oxide-Semiconductor (CMOS) manufacturing technology. (author)