The software giant claims that Motorola phones that use Google's increasingly popular Android operating system infringe on patents it holds covering functions including calendars, contacts, email synchronisation and scheduling.
The suit is an attack on the Android system on the eve of the launch of a Microsoft product, Windows Phone 7, that will compete with it.
Android has been enormously successful, overtaking Apple's operating system for popularity this year.
Microsoft corporate vice president and deputy general counsel of intellectual property and licensing Horacio Gutierrez said that Microsoft had to file the suit.
"We have a responsibility to our customers, partners, and shareholders to safeguard the billions of dollars we invest each year in bringing innovative software products and services to market. Motorola needs to stop its infringement of our patented inventions in its Android smartphones," he said.
Gutierrez told the Financial Times newspaper that the action targeted features that were part of the operating system. "The patented features implicated in the action are in the Android platform", not in added technology invented by Motorola, he said.
Microsoft has filed its claim with the US District Court for the Western District of Washington and the International Trade Commission. The claim covers nine Microsoft patents.
"The patents at issue relate to a range of functionality embodied in Motorola’s Android smartphone devices that are essential to the smartphone user experience, including synchronizing email, calendars and contacts, scheduling meetings, and notifying applications of changes in signal strength and battery power," said Gutierrez.
Android handsets are the subject of other patent claims. Apple launched a suit against phone maker HTC earlier this year claiming that its Android handsets violated some of its patents.
HTC issued a counter-claim, saying that Apple's technology infringed HTC patents.
Business software maker Oracle sued Google directly earlier this year, claiming that Android infringes patents it holds in Java technology. It acquired Java inventor Sun Microsystems last year.
