After lackluster results selling devices made by other companies, Google is giving hardware another try — this time with a smartphone made by a company it owns. On Thursday, Motorola Mobility, the handset maker Google bought last year for $12.5 billion and then retooled, introduced the Moto X, the company’s first major device since the deal.

The phone has all the standard features expected of today’s top smartphone, with a twist: the ability to control the phone by talking to it, without lifting a finger.

The stakes are big for Google, and not only because of the high price that it paid for Motorola. Google is enormously profitable, but its growth is slowing because of lagging ad sales. Finding success with the new phone could lead to a new source of revenue and a way to get more users to view the company’s ads.