Looking for a DSLR with Sony sensor inside, NIKON uses Sony EXMOR CMOS sensor in their DSLR. But there is no confirmation about what is the sensor used in NIKON D3300.
There is no definite answer to the question, unless anyone can find a teardown that shows the part number for the sensor.
Nikon use sensors from Aptina, Sony, Toshiba and their own designs, many of which offer excellent dynamic range at base ISO (on a par with Sony EXMOR). I suggest you look at test results for the D3300 on DXO mark and ignore the sensor manufacturer.
The sensor is Sony IMX-193-AQK.
This is like a year late. I was looking for the sensor's spec sheet, but never found it.
- List of all Nikon DSLR cameras and their sensor manufacturer/designer at nikonrumors.com.