Amazon lost share in the public cloud business in the fourth quarter, while Microsoft continued to gain momentum, according to research from KeyBanc analysts.

Amazon Web Services had 62 percent market share in the quarter, down from 68 percent a year earlier, KeyBanc's Brent Bracelin and other analysts wrote in a note on Thursday. Microsoft Azure jumped from 16 percent to 20 percent, and Google's share increased from 10 percent to 12 percent, they said.

According to KeyBanc, Azure likely contributed $3.7 billion to Microsoft's fiscal 2017 revenue, which totaled an estimated $96.6 billion. That suggests Azure almost doubled, which is consistent with Microsoft's disclosures about Azure's revenue growth in recent quarters.

Amazon, meanwhile, said that AWS grew 42 percent in the third quarter.

The analysts expect Azure's revenue growth to slow in fiscal year 2018 to 88 percent.

The KeyBanc report compared the big three cloud providers' artificial intelligence tools and found that Microsoft "has more pre-built models than other public cloud vendors" and makes them available from more data centers around the world.

Citing Azure growth as well as Microsoft's opportunities in AI, the analysts raised Microsoft's 12-month price target from $94 to $106. The stock closed at $89.60 on Friday.

"After our conversations with leaders at Microsoft, we came away believing the majority of revenue will come from the surrounding infrastructure costs, rather than the monetization of specific AI services, due to the required intensive model training and ongoing inference," Bracelin and the other analysts wrote.