yes some mtech courses can be done after bsc like mtech in material science engineering of mysore university.if you look at nano technology and material engineering courses ,these students are allowed to do mtech contact your university.for streams like mtech in electronics,civil,mech you should have BE/BTECH/AMIE it is must.you can persue mtech after your MSC course for subjects like electronics after attending GATE exams .for more details contact mysore university website metallurgy and material science engineering section