Motorola has seen fourth-quarter earnings nearly double compared to the same period a year ago.
The Razr has helped Motorola into second place behind Nokia
The firm, second-largest mobile phone maker after Nokia, made a net profit of $1.2bn (£682m), from $647m in 2005.
It said if had been helped by strong sales of its mobile phones, including its new ultra-slim Razr phones.
In total Motorola shipped 44.7 million handsets in the October to December quarter, up 40% on a year earlier, and giving it a world market share of 19%.
The Razr phone has sold more than 12 million units across the world since it was launched over a year ago, and has revived the company's fortunes.
The company said it expects first-quarter sales of between $9.3bn and $9.5bn.
Shares dropped $1.65, or nearly 7 percent, to $22.70 in after-hours trade.