Aug 13 (Reuters) - Applied Materials ( AMAT ) forecast fourth-quarter revenue above Wall Street expectations on Thursday, betting that unabated demand for advanced AI chips will continue to fuel robust spending on its semiconductor manufacturing equipment.

Yet, its shares fell 5% in extended trading on high investor expectations heading into the results. The stock has more than doubled this year.

Expectations were elevated as the chip equipment maker reports after peers such as Lam Research and KLA Corp posted solid quarterly performances and forecast revenue growth, said Stifel's Brian Chin.

Applied Materials ( AMAT ) forecast fourth-quarter revenue of around $10.25 billion, plus or minus $500 million, compared with analysts' average estimate of $9.54 billion, according to data compiled by LSEG.

The company, which supplies tools for key wafer fabrication processes such as physical vapor deposition and ion implantation, is benefiting from increased spending by chipmakers to support a rapid build-out of AI infrastructure.

"We expect continued strong revenue growth in the second half of the calendar year, particularly in DRAM as well as leading-edge foundry-logic and advanced packaging," Chief Financial Officer Brice Hill said.

The company reported revenue of $9.12 billion for the third quarter ended July 26, beating the estimate of $8.99 billion.