Actually not really :-) Total office space in the San Jose and 'South bay' area, which covers about 1/2 of what people think of as Silicon valley (people in Mtn View, Palo Alto, Atherton, and Fremont and Milpitas aren't 'south bay' but are often lumped into the Silicon Valley pile. Is over 109M square feet[1], the 'sprawling suburban square miles' add an additional 50M square feet. Midtown Manhattan was at 143M square feet in in 2013 [2], but I'll grant you its surprisingly similar.

What tall buildings give you of course is easier mass transit since you get better economies making a few stations which can serve a million, rather than a lot of stations that serve only thousands.

[1] Total office inventory in the South Bay/San Jose market area amounted to 106,215,509 square feet in 4,417 buildings as of the end of the second quarter 2009. -- Pg 12, https://www.sanjoseca.gov/DocumentCenter/View/1623

[2] 142,809,572 (table 1) -- http://www.thesquarefoot.com/blog/posts/manhattan-q3-2013-of...

Along with that there is an added efficiency to in person meetings, if everyone works within a mile of one another.

Why would you want to?