A semiconductor device including an isolation region located in a substrate, an NMOS device located partially over a surface of the substrate, and a PMOS device isolated from the NMOS device by the isolation region and located partially over the surface. The neutron source in accordance with the invention may include a capsule into which the neutron emitting material is loaded and a guide wire. Therefore, the thickness of the thin wall cap can approximately be reduced to 3 mm. This layer produces small, uniform grains in the remaining Al layer, which promotes a uniform oxidation of the Al between its upper and lower surfaces by the subsequent radical oxidation.