New research shows that Apple is the largest smartphone maker in the US and the third largest worldwide.

The numbers confirm that the iPhone beat out various Motorola phones to garner the most US sales this quarter, selling 8.8 million iPhones in relation to Motorola’s 8.5 million.

Those numbers are down 6.2 million for Motorola from the same quarter last year, though the company is focusing on selling smaller numbers of higher market smartphones.

Globally, Apple has maintained the third spot in the smartphone market, right behind RIM and Nokia.  Apple reached a 3% global market share among all phone makers, with a 16.4% share in the smartphone market.

The growth could be attributed to a huge growth in smartphone sales, which are reported to be up nearly 50% in the first quarter of 2010. Fifty-four million smartphones were shipped in the first quarter of 2010, in contrast to the 36 million sold in the same quarter last year.

In Japan alone, the iPhone jumped to take a 72% share of the country’s smartphone market. That share has doubled in less than a year, with an increase of 1.69 million units sold last year.