Apple's stock price will likely get a boost in the second half of the year from new products, including a bigger iPhone 6 to compete with ever-increasing screen sizes from competitors, Steve Milunovich of UBS said Monday.

"The next couple of quarters still look a little tough," he said on CNBC's "Halftime Report," adding that channel checks are suggesting slowing demand for iPhone and iPad orders, making for soft quarterly results in March and June.

"Investors are really looking out for the second calendar half, when we're likely to get the larger-screen iPhone 6," he said. "I think there's going to be pent-up demand for that."

Milunovich, who covers information technology hardware, is UBS' managing director, U.S. research group. He holds a long position in Apple and a $625 price target on the stock with a "buy" rating.

He said that he expected Apple to see a boost from new products, whether in new wearable technology or a Comcast deal for streaming content, as a Wall Street Journal report mentioned. "It's becoming clear the company wants to do more with Apple TV," he said.

Milunovich said that he was expecting two iPhone 6 models, one with a 4.7-inch screen and one with a 5.5-inch screen. The larger screen size could be seen as competition to smartphone options from such rivals as Samsung and HTC.

(Watch video: Apple & Comcast talk streaming TV: WSJ)

"But I do have some faith that you're going to see interesting products from Apple later this year," he said.

Disclosure: Comcast is the owner of NBCUniversal, the parent company of CNBC and CNBC.com.

—By CNBC's Bruno J. Navarro. Follow him on Twitter @Bruno_J_Navarro.