In this paper,total dose responses and reliability issues of MOSFETs fabricated by 65 nm CMOS technology were examined. “Radiation-induced narrow channel effect” is observed in a narrow channel device.Similar to total dose responses of NMOSFETs,narrow channel NMOSFEs have larger hot-carrier-induced degradation than wide channel devices.Step Time-Dependent Dielectric Breakdown(TDDB) stresses are applied,and narrow channel devices have higher breakdown voltage than wide channel devices,which agree with “weakest link” theory of TDDB.Experimental results show that linear current,transconductance,saturated drain current and subthreshold swing are superposed degenerated by total dose irradiation and reliability issues,which may result in different lifetime from that considering total dose irradiation reliability issues separately. In this paper, total dose responses and reliability issues of MOSFETs fabricated by 65 nm CMOS technology were examined. “Radiation-induced narrow channel effect ” is observed in a narrow channel device.Similar to total dose responses of NMOSFETs, narrow channel NMOSFEs have larger hot-carrier-induced degradation than wide channel devices, which agree with “weakest link ” theory of TDDB. Experimental results show that linear current, transconductance, saturated drain current and subthreshold swing are superposed degenerated by total dose irradiation and reliability issues, which may result in different lifetime from that accounting total dose irradiation reliability separately.