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We investigate the star formation activity in the molecular complexassociated with the Galactic HII region Sh2-90, using radio-continuum mapsobtained at 1280 MHz and 610 MHz, Herschel Hi-GAL observations at 70 -- 500microns, and deep near-infrared observation at JHK bands, along with Spitzerobservations. Sh2-90 presents a bubble morphology in the mid-IR (size ~ 0.9 pcx 1.6 pc). Radio observations suggest it is an evolved HII region with anelectron density ~ 144 cm^-3, emission measure ~ 6.7 x 10^4 cm^-6 pc and aionized mass ~ 55 Msun. From Hi-GAL observations it is found that the HIIregion is part of an elongated extended molecular cloud (size ~ 5.6 pc x 9.7pc, H_2 column density >= 3 x 10^21 cm^-2 and dust temperature 18 -- 27 K) oftotal mass >= 1 x 10^4 Msun. We identify the ionizing cluster of Sh2-90, themain exciting star being an O8--O9 V star. Five cold dust clumps (mass ~ 8 --95 Msun), four mid-IR blobs around B stars, and a compact HII region are foundat the edge of the bubble.The velocity information derived from CO (J=3-2) datacubes suggests that most of them are associated with the Sh2-90 region. 129YSOs are identified (Class I, Class II, and near-IR excess sources). Themajority of the YSOs are low mass (<= 3 Msun) sources and they are distributedmostly in the regions of high column density. Four candidate Class 0/I MYSOshave been found; they will possibly evolve to stars of mass >= 15 Msun. Wesuggest multi-generation star formation is present in the complex. From theevidences of interaction, the time scales involved and the evolutionary statusof stellar/protostellar sources, we argue that the star formation at theimmediate border/edges of Sh2-90 might have been triggered by the expanding HIIregion. However, several young sources in this complex are probably formed bysome other processes.

The molecular complex associated with the Galactic HII region Sh2-90: a possible site of triggered star formation