There is no such thing as single channel DDR3 or dual channel DDR3 or DDR2. But you may have single-sided or double-sided RAM sticks.
Single channel, dual channel and triple channel are motherboard-specific terms.
If you install one RAM stick in a dual-channel motherboard or triple-channel motherboard ( the slot where you install that one RAM stick is important. Otherwise, you get no channel at all. ), motherboard operates the RAM stick in single channel mode.
Hope this clarifies.