Root with Kingo root; stuck at turn on screen

This morning I root my phone with Kingo Root. This night my phone suddenly turned off and restarted while I was browsing with Chrome. Then it permanently stuck at one of the turn on screen. I tried factory reset by - Home + Power + Volume Up but my phone has no response. But restart by Home + Power + Volume Down works. I am using a Samsung A7. Does anyone experience this before? Anyone providing other suggestions? Thanks, Simon