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.