Sequans shares were down 15 percent from their IPO price, while STAG, which is looking to own and lease industrial property, fell more than 4 percent.
The IPOs follow two high-profile deals on Thursday -- car-sharing service Zipcar Inc and McDonald's largest South American franchisee, Arcos Dorados. Both generated enough demand to price above the proposed range and soar in their first day of trading.
"These companies are coming in a week when there are eight deals and two really, really strong ones... This week, if you weren't Zipcar, if you weren't Arcos, it wasn't great," said Morningstar IPO strategist Bill Buhr.
"Investors and the market in general continue to have a lot of discernment for deals that are fundamentally sound versus the deals that, to me, don't have a real advantage."
Sequans IPO follows tepid market responses to previous initial public offerings in the semiconductor sector: BCD Semiconductor Manufacturing Ltd, NeoPhotonics and MagnaChip Semiconductor.
Led by Apple's red-hot iPhones and iPads, the exploding market for mobile devices connected to the Internet has become the focus of much of the semiconductor industry.
STAG, which expects to operate as a real estate investment trust, plans to buy, own and manage warehouses, distribution centers, manufacturing properties and office buildings around the United States.
The industry, closely tied to economic activity, bottomed out with the economic crisis. But it is now poised for a rebound as ripples spread from the $8.7 billion acquisition of ProLogis by rival AMB Property Corp and as Blackstone Group LP is betting on the sector.
Sequans and its shareholders sold 7.7 million shares for $10 each in the IPO, raising $77 million. They had planned to sell 9.2 million at $11 to $13 and use the proceeds for general corporate purposes that may include acquisitions.
The shares were down 15 percent at $8.50 in afternoon NYSE trading.
STAG sold 13.8 million shares for $13 each in its IPO, raising about $179 million. It had planned to sell the shares for $15 to $17 each and use proceeds mostly to pay down mortgages and loans.
Shares of STAG were down 4.3 percent at $12.44.
Arcos Dorados and Zipcar also eased off, with Arcos down 0.5 percent to $21.10 and Zipcar falling 3 percent to $27.25.
UBS Investment Bank and Jefferies led underwriters on the Sequans offering. Bank of America Merrill Lynch, JPMorgan and UBS led underwriters on STAG's IPO.