The image shown on your camera LCD is NOT the RAW data file. It is a post processed JPEG Basic that is imbedded in the RAW data file.
By the same token, the histogram shown on your camera is NOT from the RAW data file but from the same post processed JPEG Basic image.
At any rate a noisy image is usually the result of using a high ISO setting, or underexposing and then increasing the exposure in post processing.
Additionally, RAW data files are captured in a 12-bit color depth by the D90 and converted to the 16-bit color depth as an image.
The Elements workspace is limited to an 8-bit color depth which is one of the reasons Elements is far less expensive than the full-featured Photoshop CS.
However, you can view and edit RAW data files in the 16-bit color depth in Adobe Camera RAW (ACR) by selecting "16-bits per channel" at the bottom of the ACR screen.