According to reports from Bloomberg, the company is working on a 7-inch version that can make calls as well as a massive 12-inch version.
The report said that sources close to the company said that both version would run on ARM-based Qualcomm chips, running Windows RT. The pair is set to launch towards the end of next year.
Windows RT will only run apps pre-installed by Microsoft, including Office 13, or those downloaded from the company’s Windows Store.
The firm is said not to be planning Intel x86-based Windows tablets as this would push the price of such tablets over $1,000, too much for most tablet buyers.
Microsoft said that more than 40 million Windows 8 licenses have been sold since the OS was released. But the firm wouldn’t comment on sales of its iPad rival the Surface RT, which is thought to be selling well below expectations.
Apple has sold 3 million iPads over the first three days following the launch of the iPad mini in early November.