Provided is a radiation-tolerant unit MOSFET to block a leakage current path caused by a total ionizing dose effect and reduce influence of a current pulse generated due to a single event effect. The radiation-tolerant unit MOSFET includes a poly gate layer for designating a gate region and at least one dummy gate region, a source and a drain, and a P+ layer and a P-active layer for specifying a P+ region to the source and the drain, and a dummy drain allowing application of a voltage. An electronic part that may normally operate is provided even a radiation environment where particle radiation and electromagnetic radiation are present.